add signature filter for MPEG7 video signature

This filter does not implement all features of MPEG7. Missing features:
- compression of signature files
- work only on (cropped) parts of the video

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

6 files changed, 1912 insertions, 1 deletions

diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 428251f71c..a48ca0ab45 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -280,6 +280,7 @@ OBJS-$(CONFIG_SHUFFLEFRAMES_FILTER)          += vf_shuffleframes.o
 OBJS-$(CONFIG_SHUFFLEPLANES_FILTER)          += vf_shuffleplanes.o
 OBJS-$(CONFIG_SIDEDATA_FILTER)               += f_sidedata.o
 OBJS-$(CONFIG_SIGNALSTATS_FILTER)            += vf_signalstats.o
+OBJS-$(CONFIG_SIGNATURE_FILTER)              += vf_signature.o
 OBJS-$(CONFIG_SMARTBLUR_FILTER)              += vf_smartblur.o
 OBJS-$(CONFIG_SOBEL_FILTER)                  += vf_convolution.o
 OBJS-$(CONFIG_SPLIT_FILTER)                  += split.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 2bf34efc84..93271fb2c4 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -290,6 +290,7 @@ static void register_all(void)
     REGISTER_FILTER(SHUFFLEPLANES,  shuffleplanes,  vf);
     REGISTER_FILTER(SIDEDATA,       sidedata,       vf);
     REGISTER_FILTER(SIGNALSTATS,    signalstats,    vf);
+    REGISTER_FILTER(SIGNATURE,      signature,      vf);
     REGISTER_FILTER(SMARTBLUR,      smartblur,      vf);
     REGISTER_FILTER(SOBEL,          sobel,          vf);
     REGISTER_FILTER(SPLIT,          split,          vf);
diff --git a/libavfilter/signature.h b/libavfilter/signature.h
new file mode 100644
index 0000000000..2659c8790e
--- /dev/null
+++ b/libavfilter/signature.h
@@ -0,0 +1,569 @@
+/*
+ * Copyright (c) 2017 Gerion Entrup
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with FFmpeg; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/**
+ * @file
+ * MPEG-7 video signature calculation and lookup filter
+ */
+
+#ifndef AVFILTER_SIGNATURE_H
+#define AVFILTER_SIGNATURE_H
+
+#include <float.h>
+#include "libavutil/common.h"
+#include "libavutil/opt.h"
+#include "libavutil/timestamp.h"
+#include "avfilter.h"
+#include "internal.h"
+
+#define ELEMENT_COUNT 10
+#define SIGELEM_SIZE 380
+#define DIFFELEM_SIZE 348 /* SIGELEM_SIZE - elem_a1 - elem_a2 */
+#define COARSE_SIZE 90
+
+enum lookup_mode {
+    MODE_OFF,
+    MODE_FULL,
+    MODE_FAST,
+    NB_LOOKUP_MODE
+};
+
+enum formats {
+    FORMAT_BINARY,
+    FORMAT_XML,
+    NB_FORMATS
+};
+
+typedef struct {
+    uint8_t x;
+    uint8_t y;
+} Point;
+
+typedef struct {
+    Point up;
+    Point to;
+} Block;
+
+typedef struct {
+    int av_elem; /* average element category */
+    short left_count; /* count of blocks that will be added together */
+    short block_count; /* count of blocks per element */
+    short elem_count;
+    const Block* blocks;
+} ElemCat;
+
+typedef struct FineSignature {
+    struct FineSignature* next;
+    struct FineSignature* prev;
+    uint64_t pts;
+    uint32_t index; /* needed for xmlexport */
+    uint8_t confidence;
+    uint8_t words[5];
+    uint8_t framesig[SIGELEM_SIZE/5];
+} FineSignature;
+
+typedef struct CoarseSignature {
+    uint8_t data[5][31]; /* 5 words with min. 243 bit */
+    struct FineSignature* first; /* associated Finesignatures */
+    struct FineSignature* last;
+    struct CoarseSignature* next;
+} CoarseSignature;
+
+/* lookup types */
+typedef struct MatchingInfo {
+    double meandist;
+    double framerateratio; /* second/first */
+    int score;
+    int offset;
+    int matchframes; /* number of matching frames */
+    int whole;
+    struct FineSignature* first;
+    struct FineSignature* second;
+    struct MatchingInfo* next;
+} MatchingInfo;
+
+typedef struct {
+    AVRational time_base;
+    /* needed for xml_export */
+    int w; /* height */
+    int h; /* width */
+
+    /* overflow protection */
+    int divide;
+
+    FineSignature* finesiglist;
+    FineSignature* curfinesig;
+
+    CoarseSignature* coarsesiglist;
+    CoarseSignature* coarseend; /* needed for xml export */
+    /* helpers to store the alternating signatures */
+    CoarseSignature* curcoarsesig1;
+    CoarseSignature* curcoarsesig2;
+
+    int coarsecount; /* counter from 0 to 89 */
+    int midcoarse;   /* whether it is a coarsesignature beginning from 45 + i * 90 */
+    uint32_t lastindex; /* helper to store amount of frames */
+
+    int exported; /* boolean whether stream already exported */
+} StreamContext;
+
+typedef struct {
+    const AVClass *class;
+    /* input parameters */
+    int mode;
+    int nb_inputs;
+    char *filename;
+    int format;
+    int thworddist;
+    int thcomposdist;
+    int thl1;
+    int thdi;
+    int thit;
+    /* end input parameters */
+
+    uint8_t l1distlut[243*242/2]; /* 243 + 242 + 241 ... */
+    StreamContext* streamcontexts;
+} SignatureContext;
+
+
+static const Block elem_a1_data[] = {
+    {{ 0, 0},{ 7, 7}},
+    {{ 8, 0},{15, 7}},
+    {{ 0, 8},{ 7,15}},
+    {{ 8, 8},{15,15}},
+    {{16, 0},{23, 7}},
+    {{24, 0},{31, 7}},
+    {{16, 8},{23,15}},
+    {{24, 8},{31,15}},
+    {{ 0,16},{ 7,23}},
+    {{ 8,16},{15,23}},
+    {{ 0,24},{ 7,31}},
+    {{ 8,24},{15,31}},
+    {{16,16},{23,23}},
+    {{24,16},{31,23}},
+    {{16,24},{23,31}},
+    {{24,24},{31,31}},
+    {{ 0, 0},{15,15}},
+    {{16, 0},{31,15}},
+    {{ 0,16},{15,31}},
+    {{16,16},{31,31}}
+};
+static const ElemCat elem_a1 = { 1, 1, 1, 20, elem_a1_data };
+
+static const Block elem_a2_data[] = {
+    {{ 2, 2},{ 9, 9}},
+    {{12, 2},{19, 9}},
+    {{22, 2},{29, 9}},
+    {{ 2,12},{ 9,19}},
+    {{12,12},{19,19}},
+    {{22,12},{29,19}},
+    {{ 2,22},{ 9,29}},
+    {{12,22},{19,29}},
+    {{22,22},{29,29}},
+    {{ 9, 9},{22,22}},
+    {{ 6, 6},{25,25}},
+    {{ 3, 3},{28,28}}
+};
+static const ElemCat elem_a2 = { 1, 1, 1, 12, elem_a2_data };
+
+static const Block elem_d1_data[] = {
+    {{ 0, 0},{ 1, 3}},{{ 2, 0},{ 3, 3}},
+    {{ 4, 0},{ 7, 1}},{{ 4, 2},{ 7, 3}},
+    {{ 0, 6},{ 3, 7}},{{ 0, 4},{ 3, 5}},
+    {{ 6, 4},{ 7, 7}},{{ 4, 4},{ 5, 7}},
+    {{ 8, 0},{ 9, 3}},{{10, 0},{11, 3}},
+    {{12, 0},{15, 1}},{{12, 2},{15, 3}},
+    {{ 8, 6},{11, 7}},{{ 8, 4},{11, 5}},
+    {{14, 4},{15, 7}},{{12, 4},{13, 7}},
+    {{ 0, 8},{ 1,11}},{{ 2, 8},{ 3,11}},
+    {{ 4, 8},{ 7, 9}},{{ 4,10},{ 7,11}},
+    {{ 0,14},{ 3,15}},{{ 0,12},{ 3,13}},
+    {{ 6,12},{ 7,15}},{{ 4,12},{ 5,15}},
+    {{ 8, 8},{ 9,11}},{{10, 8},{11,11}},
+    {{12, 8},{15, 9}},{{12,10},{15,11}},
+    {{ 8,14},{11,15}},{{ 8,12},{11,13}},
+    {{14,12},{15,15}},{{12,12},{13,15}},
+    {{16, 0},{19, 1}},{{16, 2},{19, 3}},
+    {{22, 0},{23, 3}},{{20, 0},{21, 3}},
+    {{16, 4},{17, 7}},{{18, 4},{19, 7}},
+    {{20, 6},{23, 7}},{{20, 4},{23, 5}},
+    {{24, 0},{27, 1}},{{24, 2},{27, 3}},
+    {{30, 0},{31, 3}},{{28, 0},{29, 3}},
+    {{24, 4},{25, 7}},{{26, 4},{27, 7}},
+    {{28, 6},{31, 7}},{{28, 4},{31, 5}},
+    {{16, 8},{19, 9}},{{16,10},{19,11}},
+    {{22, 8},{23,11}},{{20, 8},{21,11}},
+    {{16,12},{17,15}},{{18,12},{19,15}},
+    {{20,14},{23,15}},{{20,12},{23,13}},
+    {{24, 8},{27, 9}},{{24,10},{27,11}},
+    {{30, 8},{31,11}},{{28, 8},{29,11}},
+    {{24,12},{25,15}},{{26,12},{27,15}},
+    {{28,14},{31,15}},{{28,12},{31,13}},
+    {{ 0,16},{ 3,17}},{{ 0,18},{ 3,19}},
+    {{ 6,16},{ 7,19}},{{ 4,16},{ 5,19}},
+    {{ 0,20},{ 1,23}},{{ 2,20},{ 3,23}},
+    {{ 4,22},{ 7,23}},{{ 4,20},{ 7,21}},
+    {{ 8,16},{11,17}},{{ 8,18},{11,19}},
+    {{14,16},{15,19}},{{12,16},{13,19}},
+    {{ 8,20},{ 9,23}},{{10,20},{11,23}},
+    {{12,22},{15,23}},{{12,20},{15,21}},
+    {{ 0,24},{ 3,25}},{{ 0,26},{ 3,27}},
+    {{ 6,24},{ 7,27}},{{ 4,24},{ 5,27}},
+    {{ 0,28},{ 1,31}},{{ 2,28},{ 3,31}},
+    {{ 4,30},{ 7,31}},{{ 4,28},{ 7,29}},
+    {{ 8,24},{11,25}},{{ 8,26},{11,27}},
+    {{14,24},{15,27}},{{12,24},{13,27}},
+    {{ 8,28},{ 9,31}},{{10,28},{11,31}},
+    {{12,30},{15,31}},{{12,28},{15,29}},
+    {{16,16},{17,19}},{{18,16},{19,19}},
+    {{20,16},{23,17}},{{20,18},{23,19}},
+    {{16,22},{19,23}},{{16,20},{19,21}},
+    {{22,20},{23,23}},{{20,20},{21,23}},
+    {{24,16},{25,19}},{{26,16},{27,19}},
+    {{28,16},{31,17}},{{28,18},{31,19}},
+    {{24,22},{27,23}},{{24,20},{27,21}},
+    {{30,20},{31,23}},{{28,20},{29,23}},
+    {{16,24},{17,27}},{{18,24},{19,27}},
+    {{20,24},{23,25}},{{20,26},{23,27}},
+    {{16,30},{19,31}},{{16,28},{19,29}},
+    {{22,28},{23,31}},{{20,28},{21,31}},
+    {{24,24},{25,27}},{{26,24},{27,27}},
+    {{28,24},{31,25}},{{28,26},{31,27}},
+    {{24,30},{27,31}},{{24,28},{27,29}},
+    {{30,28},{31,31}},{{28,28},{29,31}},
+    {{ 2, 2},{ 3, 5}},{{ 4, 2},{ 5, 5}},
+    {{ 6, 2},{ 9, 3}},{{ 6, 4},{ 9, 5}},
+    {{ 2, 8},{ 5, 9}},{{ 2, 6},{ 5, 7}},
+    {{ 8, 6},{ 9, 9}},{{ 6, 6},{ 7, 9}},
+    {{12, 2},{13, 5}},{{14, 2},{15, 5}},
+    {{16, 2},{19, 3}},{{16, 4},{19, 5}},
+    {{12, 8},{15, 9}},{{12, 6},{15, 7}},
+    {{18, 6},{19, 9}},{{16, 6},{17, 9}},
+    {{22, 2},{23, 5}},{{24, 2},{25, 5}},
+    {{26, 2},{29, 3}},{{26, 4},{29, 5}},
+    {{22, 8},{25, 9}},{{22, 6},{25, 7}},
+    {{28, 6},{29, 9}},{{26, 6},{27, 9}},
+    {{ 2,12},{ 3,15}},{{ 4,12},{ 5,15}},
+    {{ 6,12},{ 9,13}},{{ 6,14},{ 9,15}},
+    {{ 2,18},{ 5,19}},{{ 2,16},{ 5,17}},
+    {{ 8,16},{ 9,19}},{{ 6,16},{ 7,19}},
+    {{12,12},{15,13}},{{12,14},{15,15}},
+    {{16,12},{19,13}},{{16,14},{19,15}},
+    {{12,18},{15,19}},{{12,16},{15,17}},
+    {{16,18},{19,19}},{{16,16},{19,17}},
+    {{22,12},{23,15}},{{24,12},{25,15}},
+    {{26,12},{29,13}},{{26,14},{29,15}},
+    {{22,18},{25,19}},{{22,16},{25,17}},
+    {{28,16},{29,19}},{{26,16},{27,19}},
+    {{ 2,22},{ 3,25}},{{ 4,22},{ 5,25}},
+    {{ 6,22},{ 9,23}},{{ 6,24},{ 9,25}},
+    {{ 2,28},{ 5,29}},{{ 2,26},{ 5,27}},
+    {{ 8,26},{ 9,29}},{{ 6,26},{ 7,29}},
+    {{12,22},{13,25}},{{14,22},{15,25}},
+    {{16,22},{19,23}},{{16,24},{19,25}},
+    {{12,28},{15,29}},{{12,26},{15,27}},
+    {{18,26},{19,29}},{{16,26},{17,29}},
+    {{22,22},{23,25}},{{24,22},{25,25}},
+    {{26,22},{29,23}},{{26,24},{29,25}},
+    {{22,28},{25,29}},{{22,26},{25,27}},
+    {{28,26},{29,29}},{{26,26},{27,29}},
+    {{ 7, 7},{10, 8}},{{ 7, 9},{10,10}},
+    {{11, 7},{12,10}},{{13, 7},{14,10}},
+    {{ 7,11},{ 8,14}},{{ 9,11},{10,14}},
+    {{11,11},{14,12}},{{11,13},{14,14}},
+    {{17, 7},{20, 8}},{{17, 9},{20,10}},
+    {{21, 7},{22,10}},{{23, 7},{24,10}},
+    {{17,11},{18,14}},{{19,11},{20,14}},
+    {{21,11},{24,12}},{{21,13},{24,14}},
+    {{ 7,17},{10,18}},{{ 7,19},{10,20}},
+    {{11,17},{12,20}},{{13,17},{14,20}},
+    {{ 7,21},{ 8,24}},{{ 9,21},{10,24}},
+    {{11,21},{14,22}},{{11,23},{14,24}},
+    {{17,17},{20,18}},{{17,19},{20,20}},
+    {{21,17},{22,20}},{{23,17},{24,20}},
+    {{17,21},{18,24}},{{19,21},{20,24}},
+    {{21,21},{24,22}},{{21,23},{24,24}}
+};
+static const ElemCat elem_d1 = { 0, 1, 2, 116, elem_d1_data };
+
+static const Block elem_d2_data[] = {
+    {{ 0, 0},{ 3, 3}},{{ 4, 4},{ 7, 7}},{{ 4, 0},{ 7, 3}},{{ 0, 4},{ 3, 7}},
+    {{ 8, 0},{11, 3}},{{12, 4},{15, 7}},{{12, 0},{15, 3}},{{ 8, 4},{11, 7}},
+    {{16, 0},{19, 3}},{{20, 4},{23, 7}},{{20, 0},{23, 3}},{{16, 4},{19, 7}},
+    {{24, 0},{27, 3}},{{28, 4},{31, 7}},{{28, 0},{31, 3}},{{24, 4},{27, 7}},
+    {{ 0, 8},{ 3,11}},{{ 4,12},{ 7,15}},{{ 4, 8},{ 7,11}},{{ 0,12},{ 3,15}},
+    {{ 8, 8},{11,11}},{{12,12},{15,15}},{{12, 8},{15,11}},{{ 8,12},{11,15}},
+    {{16, 8},{19,11}},{{20,12},{23,15}},{{20, 8},{23,11}},{{16,12},{19,15}},
+    {{24, 8},{27,11}},{{28,12},{31,15}},{{28, 8},{31,11}},{{24,12},{27,15}},
+    {{ 0,16},{ 3,19}},{{ 4,20},{ 7,23}},{{ 4,16},{ 7,19}},{{ 0,20},{ 3,23}},
+    {{ 8,16},{11,19}},{{12,20},{15,23}},{{12,16},{15,19}},{{ 8,20},{11,23}},
+    {{16,16},{19,19}},{{20,20},{23,23}},{{20,16},{23,19}},{{16,20},{19,23}},
+    {{24,16},{27,19}},{{28,20},{31,23}},{{28,16},{31,19}},{{24,20},{27,23}},
+    {{ 0,24},{ 3,27}},{{ 4,28},{ 7,31}},{{ 4,24},{ 7,27}},{{ 0,28},{ 3,31}},
+    {{ 8,24},{11,27}},{{12,28},{15,31}},{{12,24},{15,27}},{{ 8,28},{11,31}},
+    {{16,24},{19,27}},{{20,28},{23,31}},{{20,24},{23,27}},{{16,28},{19,31}},
+    {{24,24},{27,27}},{{28,28},{31,31}},{{28,24},{31,27}},{{24,28},{27,31}},
+    {{ 4, 4},{ 7, 7}},{{ 8, 8},{11,11}},{{ 8, 4},{11, 7}},{{ 4, 8},{ 7,11}},
+    {{12, 4},{15, 7}},{{16, 8},{19,11}},{{16, 4},{19, 7}},{{12, 8},{15,11}},
+    {{20, 4},{23, 7}},{{24, 8},{27,11}},{{24, 4},{27, 7}},{{20, 8},{23,11}},
+    {{ 4,12},{ 7,15}},{{ 8,16},{11,19}},{{ 8,12},{11,15}},{{ 4,16},{ 7,19}},
+    {{12,12},{15,15}},{{16,16},{19,19}},{{16,12},{19,15}},{{12,16},{15,19}},
+    {{20,12},{23,15}},{{24,16},{27,19}},{{24,12},{27,15}},{{20,16},{23,19}},
+    {{ 4,20},{ 7,23}},{{ 8,24},{11,27}},{{ 8,20},{11,23}},{{ 4,24},{ 7,27}},
+    {{12,20},{15,23}},{{16,24},{19,27}},{{16,20},{19,23}},{{12,24},{15,27}},
+    {{20,20},{23,23}},{{24,24},{27,27}},{{24,20},{27,23}},{{20,24},{23,27}}
+};
+static const ElemCat elem_d2 = { 0, 2, 4, 25, elem_d2_data };
+
+static const Block elem_d3_data[] = {
+    {{ 1, 1},{10,10}},{{11, 1},{20,10}},
+    {{ 1, 1},{10,10}},{{21, 1},{30,10}},
+    {{ 1, 1},{10,10}},{{ 1,11},{10,20}},
+    {{ 1, 1},{10,10}},{{11,11},{20,20}},
+    {{ 1, 1},{10,10}},{{21,11},{30,20}},
+    {{ 1, 1},{10,10}},{{ 1,21},{10,30}},
+    {{ 1, 1},{10,10}},{{11,21},{20,30}},
+    {{ 1, 1},{10,10}},{{21,21},{30,30}},
+    {{11, 1},{20,10}},{{21, 1},{30,10}},
+    {{11, 1},{20,10}},{{ 1,11},{10,20}},
+    {{11, 1},{20,10}},{{11,11},{20,20}},
+    {{11, 1},{20,10}},{{21,11},{30,20}},
+    {{11, 1},{20,10}},{{ 1,21},{10,30}},
+    {{11, 1},{20,10}},{{11,21},{20,30}},
+    {{11, 1},{20,10}},{{21,21},{30,30}},
+    {{21, 1},{30,10}},{{ 1,11},{10,20}},
+    {{21, 1},{30,10}},{{11,11},{20,20}},
+    {{21, 1},{30,10}},{{21,11},{30,20}},
+    {{21, 1},{30,10}},{{ 1,21},{10,30}},
+    {{21, 1},{30,10}},{{11,21},{20,30}},
+    {{21, 1},{30,10}},{{21,21},{30,30}},
+    {{ 1,11},{10,20}},{{11,11},{20,20}},
+    {{ 1,11},{10,20}},{{21,11},{30,20}},
+    {{ 1,11},{10,20}},{{ 1,21},{10,30}},
+    {{ 1,11},{10,20}},{{11,21},{20,30}},
+    {{ 1,11},{10,20}},{{21,21},{30,30}},
+    {{11,11},{20,20}},{{21,11},{30,20}},
+    {{11,11},{20,20}},{{ 1,21},{10,30}},
+    {{11,11},{20,20}},{{11,21},{20,30}},
+    {{11,11},{20,20}},{{21,21},{30,30}},
+    {{21,11},{30,20}},{{ 1,21},{10,30}},
+    {{21,11},{30,20}},{{11,21},{20,30}},
+    {{21,11},{30,20}},{{21,21},{30,30}},
+    {{ 1,21},{10,30}},{{11,21},{20,30}},
+    {{ 1,21},{10,30}},{{21,21},{30,30}},
+    {{11,21},{20,30}},{{21,21},{30,30}}
+};
+static const ElemCat elem_d3 = { 0, 1, 2, 36, elem_d3_data };
+
+static const Block elem_d4_data[] = {
+    {{ 7,13},{12,18}},{{19,13},{24,18}},
+    {{13, 7},{18,12}},{{13,19},{18,24}},
+    {{ 7, 7},{12,12}},{{19,19},{24,24}},
+    {{19, 7},{24,12}},{{ 7,19},{12,24}},
+    {{13, 7},{18,12}},{{19,13},{24,18}},
+    {{19,13},{24,18}},{{13,19},{18,24}},
+    {{13,19},{18,24}},{{ 7,13},{12,18}},
+    {{ 7,13},{12,18}},{{13, 7},{18,12}},
+    {{ 7, 7},{12,12}},{{19, 7},{24,12}},
+    {{19, 7},{24,12}},{{19,19},{24,24}},
+    {{19,19},{24,24}},{{ 7,19},{12,24}},
+    {{ 7,19},{12,24}},{{ 7, 7},{12,12}},
+    {{13,13},{18,18}},{{13, 1},{18, 6}},
+    {{13,13},{18,18}},{{25,13},{30,18}},
+    {{13,13},{18,18}},{{13,25},{18,30}},
+    {{13,13},{18,18}},{{ 1,13},{ 6,18}},
+    {{13, 1},{18, 6}},{{13,25},{18,30}},
+    {{ 1,13},{ 6,18}},{{25,13},{30,18}},
+    {{ 7, 1},{12, 6}},{{19, 1},{24, 6}},
+    {{ 7,25},{12,30}},{{19,25},{24,30}},
+    {{ 1, 7},{ 6,12}},{{ 1,19},{ 6,24}},
+    {{25, 7},{30,12}},{{25,19},{30,24}},
+    {{ 7, 1},{12, 6}},{{ 1, 7},{ 6,12}},
+    {{19, 1},{24, 6}},{{25, 7},{30,12}},
+    {{25,19},{30,24}},{{19,25},{24,30}},
+    {{ 1,19},{ 6,24}},{{ 7,25},{12,30}},
+    {{ 1, 1},{ 6, 6}},{{25, 1},{30, 6}},
+    {{25, 1},{30, 6}},{{25,25},{30,30}},
+    {{25,25},{30,30}},{{ 1,25},{ 6,30}},
+    {{ 1,25},{ 6,30}},{{ 1, 1},{ 6, 6}}
+};
+static const ElemCat elem_d4 = { 0, 1, 2, 30, elem_d4_data };
+
+static const Block elem_d5_data[] = {
+    {{ 1, 1},{10, 3}},{{ 1, 4},{ 3, 7}},{{ 8, 4},{10, 7}},{{ 1, 8},{10,10}},{{ 4, 4},{ 7, 7}},
+    {{11, 1},{20, 3}},{{11, 4},{13, 7}},{{18, 4},{20, 7}},{{11, 8},{20,10}},{{14, 4},{17, 7}},
+    {{21, 1},{30, 3}},{{21, 4},{23, 7}},{{28, 4},{30, 7}},{{21, 8},{30,10}},{{24, 4},{27, 7}},
+    {{ 1,11},{10,13}},{{ 1,14},{ 3,17}},{{ 8,14},{10,17}},{{ 1,18},{10,20}},{{ 4,14},{ 7,17}},
+    {{11,11},{20,13}},{{11,14},{13,17}},{{18,14},{20,17}},{{11,18},{20,20}},{{14,14},{17,17}},
+    {{21,11},{30,13}},{{21,14},{23,17}},{{28,14},{30,17}},{{21,18},{30,20}},{{24,14},{27,17}},
+    {{ 1,21},{10,23}},{{ 1,24},{ 3,27}},{{ 8,24},{10,27}},{{ 1,28},{10,30}},{{ 4,24},{ 7,27}},
+    {{11,21},{20,23}},{{11,24},{13,27}},{{18,24},{20,27}},{{11,28},{20,30}},{{14,24},{17,27}},
+    {{21,21},{30,23}},{{21,24},{23,27}},{{28,24},{30,27}},{{21,28},{30,30}},{{24,24},{27,27}},
+    {{ 6, 6},{15, 8}},{{ 6, 9},{ 8,12}},{{13, 9},{15,12}},{{ 6,13},{15,15}},{{ 9, 9},{12,12}},
+    {{16, 6},{25, 8}},{{16, 9},{18,12}},{{23, 9},{25,12}},{{16,13},{25,15}},{{19, 9},{22,12}},
+    {{ 6,16},{15,18}},{{ 6,19},{ 8,22}},{{13,19},{15,22}},{{ 6,23},{15,25}},{{ 9,19},{12,22}},
+    {{16,16},{25,18}},{{16,19},{18,22}},{{23,19},{25,22}},{{16,23},{25,25}},{{19,19},{22,22}},
+    {{ 6, 1},{15, 3}},{{ 6, 4},{ 8, 7}},{{13, 4},{15, 7}},{{ 6, 8},{15,10}},{{ 9, 4},{12, 7}},
+    {{16, 1},{25, 3}},{{16, 4},{18, 7}},{{23, 4},{25, 7}},{{16, 8},{25,10}},{{19, 4},{22, 7}},
+    {{ 1, 6},{10, 8}},{{ 1, 9},{ 3,12}},{{ 8, 9},{10,12}},{{ 1,13},{10,15}},{{ 4, 9},{ 7,12}},
+    {{11, 6},{20, 8}},{{11, 9},{13,12}},{{18, 9},{20,12}},{{11,13},{20,15}},{{14, 9},{17,12}},
+    {{21, 6},{30, 8}},{{21, 9},{23,12}},{{28, 9},{30,12}},{{21,13},{30,15}},{{24, 9},{27,12}},
+    {{ 6,11},{15,13}},{{ 6,14},{ 8,17}},{{13,14},{15,17}},{{ 6,18},{15,20}},{{ 9,14},{12,17}},
+    {{16,11},{25,13}},{{16,14},{18,17}},{{23,14},{25,17}},{{16,18},{25,20}},{{19,14},{22,17}},
+    {{ 1,16},{10,18}},{{ 1,19},{ 3,22}},{{ 8,19},{10,22}},{{ 1,23},{10,25}},{{ 4,19},{ 7,22}},
+    {{11,16},{20,18}},{{11,19},{13,22}},{{18,19},{20,22}},{{11,23},{20,25}},{{14,19},{17,22}},
+    {{21,16},{30,18}},{{21,19},{23,22}},{{28,19},{30,22}},{{21,23},{30,25}},{{24,19},{27,22}},
+    {{ 6,21},{15,23}},{{ 6,24},{ 8,27}},{{13,24},{15,27}},{{ 6,28},{15,30}},{{ 9,24},{12,27}},
+    {{16,21},{25,23}},{{16,24},{18,27}},{{23,24},{25,27}},{{16,28},{25,30}},{{19,24},{22,27}},
+    {{ 2, 2},{14, 6}},{{ 2, 7},{ 6, 9}},{{10, 7},{14, 9}},{{ 2,10},{14,14}},{{ 7, 7},{ 9, 9}},
+    {{ 7, 2},{19, 6}},{{ 7, 7},{11, 9}},{{15, 7},{19, 9}},{{ 7,10},{19,14}},{{12, 7},{14, 9}},
+    {{12, 2},{24, 6}},{{12, 7},{16, 9}},{{20, 7},{24, 9}},{{12,10},{24,14}},{{17, 7},{19, 9}},
+    {{17, 2},{29, 6}},{{17, 7},{21, 9}},{{25, 7},{29, 9}},{{17,10},{29,14}},{{22, 7},{24, 9}},
+    {{ 2, 7},{14,11}},{{ 2,12},{ 6,14}},{{10,12},{14,14}},{{ 2,15},{14,19}},{{ 7,12},{ 9,14}},
+    {{ 7, 7},{19,11}},{{ 7,12},{11,14}},{{15,12},{19,14}},{{ 7,15},{19,19}},{{12,12},{14,14}},
+    {{12, 7},{24,11}},{{12,12},{16,14}},{{20,12},{24,14}},{{12,15},{24,19}},{{17,12},{19,14}},
+    {{17, 7},{29,11}},{{17,12},{21,14}},{{25,12},{29,14}},{{17,15},{29,19}},{{22,12},{24,14}},
+    {{ 2,12},{14,16}},{{ 2,17},{ 6,19}},{{10,17},{14,19}},{{ 2,20},{14,24}},{{ 7,17},{ 9,19}},
+    {{ 7,12},{19,16}},{{ 7,17},{11,19}},{{15,17},{19,19}},{{ 7,20},{19,24}},{{12,17},{14,19}},
+    {{12,12},{24,16}},{{12,17},{16,19}},{{20,17},{24,19}},{{12,20},{24,24}},{{17,17},{19,19}},
+    {{17,12},{29,16}},{{17,17},{21,19}},{{25,17},{29,19}},{{17,20},{29,24}},{{22,17},{24,19}},
+    {{ 2,17},{14,21}},{{ 2,22},{ 6,24}},{{10,22},{14,24}},{{ 2,25},{14,29}},{{ 7,22},{ 9,24}},
+    {{ 7,17},{19,21}},{{ 7,22},{11,24}},{{15,22},{19,24}},{{ 7,25},{19,29}},{{12,22},{14,24}},
+    {{12,17},{24,21}},{{12,22},{16,24}},{{20,22},{24,24}},{{12,25},{24,29}},{{17,22},{19,24}},
+    {{17,17},{29,21}},{{17,22},{21,24}},{{25,22},{29,24}},{{17,25},{29,29}},{{22,22},{24,24}},
+    {{ 8, 3},{13, 4}},{{ 8, 5},{ 9, 6}},{{12, 5},{13, 6}},{{ 8, 7},{13, 8}},{{10, 5},{11, 6}},
+    {{13, 3},{18, 4}},{{13, 5},{14, 6}},{{17, 5},{18, 6}},{{13, 7},{18, 8}},{{15, 5},{16, 6}},
+    {{18, 3},{23, 4}},{{18, 5},{19, 6}},{{22, 5},{23, 6}},{{18, 7},{23, 8}},{{20, 5},{21, 6}},
+    {{ 3, 8},{ 8, 9}},{{ 3,10},{ 4,11}},{{ 7,10},{ 8,11}},{{ 3,12},{ 8,13}},{{ 5,10},{ 6,11}},
+    {{ 8, 8},{13, 9}},{{ 8,10},{ 9,11}},{{12,10},{13,11}},{{ 8,12},{13,13}},{{10,10},{11,11}},
+    {{13, 8},{18, 9}},{{13,10},{14,11}},{{17,10},{18,11}},{{13,12},{18,13}},{{15,10},{16,11}},
+    {{18, 8},{23, 9}},{{18,10},{19,11}},{{22,10},{23,11}},{{18,12},{23,13}},{{20,10},{21,11}},
+    {{23, 8},{28, 9}},{{23,10},{24,11}},{{27,10},{28,11}},{{23,12},{28,13}},{{25,10},{26,11}},
+    {{ 3,13},{ 8,14}},{{ 3,15},{ 4,16}},{{ 7,15},{ 8,16}},{{ 3,17},{ 8,18}},{{ 5,15},{ 6,16}},
+    {{ 8,13},{13,14}},{{ 8,15},{ 9,16}},{{12,15},{13,16}},{{ 8,17},{13,18}},{{10,15},{11,16}},
+    {{13,13},{18,14}},{{13,15},{14,16}},{{17,15},{18,16}},{{13,17},{18,18}},{{15,15},{16,16}},
+    {{18,13},{23,14}},{{18,15},{19,16}},{{22,15},{23,16}},{{18,17},{23,18}},{{20,15},{21,16}},
+    {{23,13},{28,14}},{{23,15},{24,16}},{{27,15},{28,16}},{{23,17},{28,18}},{{25,15},{26,16}},
+    {{ 3,18},{ 8,19}},{{ 3,20},{ 4,21}},{{ 7,20},{ 8,21}},{{ 3,22},{ 8,23}},{{ 5,20},{ 6,21}},
+    {{ 8,18},{13,19}},{{ 8,20},{ 9,21}},{{12,20},{13,21}},{{ 8,22},{13,23}},{{10,20},{11,21}},
+    {{13,18},{18,19}},{{13,20},{14,21}},{{17,20},{18,21}},{{13,22},{18,23}},{{15,20},{16,21}},
+    {{18,18},{23,19}},{{18,20},{19,21}},{{22,20},{23,21}},{{18,22},{23,23}},{{20,20},{21,21}},
+    {{23,18},{28,19}},{{23,20},{24,21}},{{27,20},{28,21}},{{23,22},{28,23}},{{25,20},{26,21}},
+    {{ 8,23},{13,24}},{{ 8,25},{ 9,26}},{{12,25},{13,26}},{{ 8,27},{13,28}},{{10,25},{11,26}},
+    {{13,23},{18,24}},{{13,25},{14,26}},{{17,25},{18,26}},{{13,27},{18,28}},{{15,25},{16,26}},
+    {{18,23},{23,24}},{{18,25},{19,26}},{{22,25},{23,26}},{{18,27},{23,28}},{{20,25},{21,26}}
+};
+static const ElemCat elem_d5 = { 0, 4, 5, 62, elem_d5_data };
+
+static const Block elem_d6_data[] = {
+    {{ 3, 5},{12,10}},{{ 5, 3},{10,12}},
+    {{11, 5},{20,10}},{{13, 3},{18,12}},
+    {{19, 5},{28,10}},{{21, 3},{26,12}},
+    {{ 3,13},{12,18}},{{ 5,11},{10,20}},
+    {{11,13},{20,18}},{{13,11},{18,20}},
+    {{19,13},{28,18}},{{21,11},{26,20}},
+    {{ 3,21},{12,26}},{{ 5,19},{10,28}},
+    {{11,21},{20,26}},{{13,19},{18,28}},
+    {{19,21},{28,26}},{{21,19},{26,28}}
+};
+static const ElemCat elem_d6 = { 0, 1, 2, 9, elem_d6_data };
+
+static const Block elem_d7_data[] = {
+    {{ 0, 4},{ 3, 7}},{{ 8, 4},{11, 7}},{{ 4, 4},{ 7, 7}},
+    {{ 4, 0},{ 7, 3}},{{ 4, 8},{ 7,11}},{{ 4, 4},{ 7, 7}},
+    {{ 5, 4},{ 8, 7}},{{13, 4},{16, 7}},{{ 9, 4},{12, 7}},
+    {{ 9, 0},{12, 3}},{{ 9, 8},{12,11}},{{ 9, 4},{12, 7}},
+    {{10, 4},{13, 7}},{{18, 4},{21, 7}},{{14, 4},{17, 7}},
+    {{14, 0},{17, 3}},{{14, 8},{17,11}},{{14, 4},{17, 7}},
+    {{15, 4},{18, 7}},{{23, 4},{26, 7}},{{19, 4},{22, 7}},
+    {{19, 0},{22, 3}},{{19, 8},{22,11}},{{19, 4},{22, 7}},
+    {{20, 4},{23, 7}},{{28, 4},{31, 7}},{{24, 4},{27, 7}},
+    {{24, 0},{27, 3}},{{24, 8},{27,11}},{{24, 4},{27, 7}},
+    {{ 0, 9},{ 3,12}},{{ 8, 9},{11,12}},{{ 4, 9},{ 7,12}},
+    {{ 4, 5},{ 7, 8}},{{ 4,13},{ 7,16}},{{ 4, 9},{ 7,12}},
+    {{ 5, 9},{ 8,12}},{{13, 9},{16,12}},{{ 9, 9},{12,12}},
+    {{ 9, 5},{12, 8}},{{ 9,13},{12,16}},{{ 9, 9},{12,12}},
+    {{10, 9},{13,12}},{{18, 9},{21,12}},{{14, 9},{17,12}},
+    {{14, 5},{17, 8}},{{14,13},{17,16}},{{14, 9},{17,12}},
+    {{15, 9},{18,12}},{{23, 9},{26,12}},{{19, 9},{22,12}},
+    {{19, 5},{22, 8}},{{19,13},{22,16}},{{19, 9},{22,12}},
+    {{20, 9},{23,12}},{{28, 9},{31,12}},{{24, 9},{27,12}},
+    {{24, 5},{27, 8}},{{24,13},{27,16}},{{24, 9},{27,12}},
+    {{ 0,14},{ 3,17}},{{ 8,14},{11,17}},{{ 4,14},{ 7,17}},
+    {{ 4,10},{ 7,13}},{{ 4,18},{ 7,21}},{{ 4,14},{ 7,17}},
+    {{ 5,14},{ 8,17}},{{13,14},{16,17}},{{ 9,14},{12,17}},
+    {{ 9,10},{12,13}},{{ 9,18},{12,21}},{{ 9,14},{12,17}},
+    {{10,14},{13,17}},{{18,14},{21,17}},{{14,14},{17,17}},
+    {{14,10},{17,13}},{{14,18},{17,21}},{{14,14},{17,17}},
+    {{15,14},{18,17}},{{23,14},{26,17}},{{19,14},{22,17}},
+    {{19,10},{22,13}},{{19,18},{22,21}},{{19,14},{22,17}},
+    {{20,14},{23,17}},{{28,14},{31,17}},{{24,14},{27,17}},
+    {{24,10},{27,13}},{{24,18},{27,21}},{{24,14},{27,17}},
+    {{ 0,19},{ 3,22}},{{ 8,19},{11,22}},{{ 4,19},{ 7,22}},
+    {{ 4,15},{ 7,18}},{{ 4,23},{ 7,26}},{{ 4,19},{ 7,22}},
+    {{ 5,19},{ 8,22}},{{13,19},{16,22}},{{ 9,19},{12,22}},
+    {{ 9,15},{12,18}},{{ 9,23},{12,26}},{{ 9,19},{12,22}},
+    {{10,19},{13,22}},{{18,19},{21,22}},{{14,19},{17,22}},
+    {{14,15},{17,18}},{{14,23},{17,26}},{{14,19},{17,22}},
+    {{15,19},{18,22}},{{23,19},{26,22}},{{19,19},{22,22}},
+    {{19,15},{22,18}},{{19,23},{22,26}},{{19,19},{22,22}},
+    {{20,19},{23,22}},{{28,19},{31,22}},{{24,19},{27,22}},
+    {{24,15},{27,18}},{{24,23},{27,26}},{{24,19},{27,22}},
+    {{ 0,24},{ 3,27}},{{ 8,24},{11,27}},{{ 4,24},{ 7,27}},
+    {{ 4,20},{ 7,23}},{{ 4,28},{ 7,31}},{{ 4,24},{ 7,27}},
+    {{ 5,24},{ 8,27}},{{13,24},{16,27}},{{ 9,24},{12,27}},
+    {{ 9,20},{12,23}},{{ 9,28},{12,31}},{{ 9,24},{12,27}},
+    {{10,24},{13,27}},{{18,24},{21,27}},{{14,24},{17,27}},
+    {{14,20},{17,23}},{{14,28},{17,31}},{{14,24},{17,27}},
+    {{15,24},{18,27}},{{23,24},{26,27}},{{19,24},{22,27}},
+    {{19,20},{22,23}},{{19,28},{22,31}},{{19,24},{22,27}},
+    {{20,24},{23,27}},{{28,24},{31,27}},{{24,24},{27,27}},
+    {{24,20},{27,23}},{{24,28},{27,31}},{{24,24},{27,27}}
+};
+static const ElemCat elem_d7 = { 0, 2, 3, 50, elem_d7_data };
+
+static const Block elem_d8_data[] = {
+    {{ 0, 0},{ 7, 3}},{{ 0, 4},{ 7, 7}},
+    {{ 8, 0},{11, 7}},{{12, 0},{15, 7}},
+    {{ 0, 8},{ 3,15}},{{ 4, 8},{ 7,15}},
+    {{ 8, 8},{15,11}},{{ 8,12},{15,15}},
+    {{16, 0},{19, 7}},{{20, 0},{23, 7}},
+    {{24, 0},{31, 3}},{{24, 4},{31, 7}},
+    {{16, 8},{23,11}},{{16,12},{23,15}},
+    {{24, 8},{27,15}},{{28, 8},{31,15}},
+    {{ 0,16},{ 3,23}},{{ 4,16},{ 7,23}},
+    {{ 8,16},{15,19}},{{ 8,20},{15,23}},
+    {{ 0,24},{ 7,27}},{{ 0,28},{ 7,31}},
+    {{ 8,24},{11,31}},{{12,24},{15,31}},
+    {{16,16},{23,19}},{{16,20},{23,23}},
+    {{24,16},{27,23}},{{28,16},{31,23}},
+    {{16,24},{19,31}},{{20,24},{23,31}},
+    {{24,24},{31,27}},{{24,28},{31,31}},
+    {{ 0, 0},{ 7,15}},{{ 8, 0},{15,15}},
+    {{16, 0},{31, 7}},{{16, 8},{31,15}},
+    {{ 0,16},{15,23}},{{ 0,24},{15,31}},
+    {{16,16},{23,31}},{{24,16},{31,31}}
+};
+static const ElemCat elem_d8 = { 0, 1, 2, 20, elem_d8_data };
+
+static const ElemCat* elements[ELEMENT_COUNT] = { &elem_a1, &elem_a2,
+                                                  &elem_d1, &elem_d2, &elem_d3, &elem_d4,
+                                                  &elem_d5, &elem_d6, &elem_d7, &elem_d8 };
+#endif /* AVFILTER_SIGNATURE_H */
diff --git a/libavfilter/signature_lookup.c b/libavfilter/signature_lookup.c
new file mode 100644
index 0000000000..5bc2904409
--- /dev/null
+++ b/libavfilter/signature_lookup.c
@@ -0,0 +1,573 @@
+/*
+ * Copyright (c) 2017 Gerion Entrup
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with FFmpeg; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/**
+ * @file
+ * MPEG-7 video signature calculation and lookup filter
+ */
+
+#include "signature.h"
+
+#define HOUGH_MAX_OFFSET 90
+#define MAX_FRAMERATE 60
+
+#define DIR_PREV 0
+#define DIR_NEXT 1
+#define DIR_PREV_END 2
+#define DIR_NEXT_END 3
+
+#define STATUS_NULL 0
+#define STATUS_END_REACHED 1
+#define STATUS_BEGIN_REACHED 2
+
+static void fill_l1distlut(uint8_t lut[])
+{
+    int i, j, tmp_i, tmp_j,count;
+    uint8_t dist;
+
+    for (i = 0, count = 0; i < 242; i++) {
+        for (j = i + 1; j < 243; j++, count++) {
+            /* ternary distance between i and j */
+            dist = 0;
+            tmp_i = i; tmp_j = j;
+            do {
+                dist += FFABS((tmp_j % 3) - (tmp_i % 3));
+                tmp_j /= 3;
+                tmp_i /= 3;
+            } while (tmp_i > 0 || tmp_j > 0);
+            lut[count] = dist;
+        }
+    }
+}
+
+static unsigned int intersection_word(const uint8_t *first, const uint8_t *second)
+{
+    unsigned int val=0,i;
+    for (i = 0; i < 28; i += 4) {
+        val += av_popcount( (first[i]   & second[i]  ) << 24 |
+                            (first[i+1] & second[i+1]) << 16 |
+                            (first[i+2] & second[i+2]) << 8  |
+                            (first[i+3] & second[i+3]) );
+    }
+    val += av_popcount( (first[28] & second[28]) << 16 |
+                        (first[29] & second[29]) << 8  |
+                        (first[30] & second[30]) );
+    return val;
+}
+
+static unsigned int union_word(const uint8_t *first, const uint8_t *second)
+{
+    unsigned int val=0,i;
+    for (i = 0; i < 28; i += 4) {
+        val += av_popcount( (first[i]   | second[i]  ) << 24 |
+                            (first[i+1] | second[i+1]) << 16 |
+                            (first[i+2] | second[i+2]) << 8  |
+                            (first[i+3] | second[i+3]) );
+    }
+    val += av_popcount( (first[28] | second[28]) << 16 |
+                        (first[29] | second[29]) << 8  |
+                        (first[30] | second[30]) );
+    return val;
+}
+
+static unsigned int get_l1dist(AVFilterContext *ctx, SignatureContext *sc, const uint8_t *first, const uint8_t *second)
+{
+    unsigned int i;
+    unsigned int dist = 0;
+    uint8_t f, s;
+
+    for (i = 0; i < SIGELEM_SIZE/5; i++) {
+        if (first[i] != second[i]) {
+            f = first[i];
+            s = second[i];
+            if (f > s) {
+                /* little variation of gauss sum formula */
+                dist += sc->l1distlut[243*242/2 - (243-s)*(242-s)/2 + f - s - 1];
+            } else {
+                dist += sc->l1distlut[243*242/2 - (243-f)*(242-f)/2 + s - f - 1];
+            }
+        }
+    }
+    return dist;
+}
+
+/**
+ * calculates the jaccard distance and evaluates a pair of coarse signatures as good
+ * @return 0 if pair is bad, 1 otherwise
+ */
+static int get_jaccarddist(SignatureContext *sc, CoarseSignature *first, CoarseSignature *second)
+{
+    int jaccarddist, i, composdist = 0, cwthcount = 0;
+    for (i = 0; i < 5; i++) {
+        if ((jaccarddist = intersection_word(first->data[i], second->data[i])) > 0) {
+            jaccarddist /= union_word(first->data[i], second->data[i]);
+        }
+        if (jaccarddist >= sc->thworddist) {
+            if (++cwthcount > 2) {
+                /* more than half (5/2) of distances are too wide */
+                return 0;
+            }
+        }
+        composdist += jaccarddist;
+        if (composdist > sc->thcomposdist) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+/**
+ * step through the coarsesignatures as long as a good candidate is found
+ * @return 0 if no candidate is found, 1 otherwise
+ */
+static int find_next_coarsecandidate(SignatureContext *sc, CoarseSignature *secondstart, CoarseSignature **first, CoarseSignature **second, int start)
+{
+    /* go one coarsesignature foreword */
+    if (!start) {
+        if ((*second)->next) {
+            *second = (*second)->next;
+        } else if ((*first)->next) {
+            *second = secondstart;
+            *first = (*first)->next;
+        } else {
+            return 0;
+        }
+    }
+
+    while (1) {
+        if (get_jaccarddist(sc, *first, *second))
+            return 1;
+
+        /* next signature */
+        if ((*second)->next) {
+            *second = (*second)->next;
+        } else if ((*first)->next) {
+            *second = secondstart;
+            *first = (*first)->next;
+        } else {
+            return 0;
+        }
+    }
+}
+
+/**
+ * compares framesignatures and sorts out signatures with a l1 distance above a given threshold.
+ * Then tries to find out offset and differences between framerates with a hough transformation
+ */
+static MatchingInfo* get_matching_parameters(AVFilterContext *ctx, SignatureContext *sc, FineSignature *first, FineSignature *second)
+{
+    FineSignature *f, *s;
+    size_t i, j, k, l, hmax = 0, score;
+    int framerate, offset, l1dist;
+    double m;
+    MatchingInfo *cands = NULL, *c = NULL;
+
+    struct {
+        uint8_t size;
+        unsigned int dist;
+        FineSignature *a;
+        uint8_t b_pos[COARSE_SIZE];
+        FineSignature *b[COARSE_SIZE];
+    } pairs[COARSE_SIZE];
+
+    typedef struct {
+        int dist;
+        size_t score;
+        FineSignature *a;
+        FineSignature *b;
+    } hspace_elem;
+
+    /* houghspace */
+    hspace_elem** hspace = av_malloc_array(MAX_FRAMERATE, sizeof(hspace_elem *));
+
+    /* initialize houghspace */
+    for (i = 0; i < MAX_FRAMERATE; i++) {
+        hspace[i] = av_malloc_array(2 * HOUGH_MAX_OFFSET + 1, sizeof(hspace_elem));
+        for (j = 0; j < HOUGH_MAX_OFFSET; j++) {
+            hspace[i][j].score = 0;
+            hspace[i][j].dist = 99999;
+        }
+    }
+
+    /* l1 distances */
+    for (i = 0, f = first; i < COARSE_SIZE && f->next; i++, f = f->next) {
+        pairs[i].size = 0;
+        pairs[i].dist = 99999;
+        pairs[i].a = f;
+        for (j = 0, s = second; j < COARSE_SIZE && s->next; j++, s = s->next) {
+            /* l1 distance of finesignature */
+            l1dist = get_l1dist(ctx, sc, f->framesig, s->framesig);
+            if (l1dist < sc->thl1) {
+                if (l1dist < pairs[i].dist) {
+                    pairs[i].size = 1;
+                    pairs[i].dist = l1dist;
+                    pairs[i].b_pos[0] = j;
+                    pairs[i].b[0] = s;
+                } else if (l1dist == pairs[i].dist) {
+                    pairs[i].b[pairs[i].size] = s;
+                    pairs[i].b_pos[pairs[i].size] = j;
+                    pairs[i].size++;
+                }
+            }
+        }
+    }
+    /* last incomplete coarsesignature */
+    if (f->next == NULL) {
+        for (; i < COARSE_SIZE; i++) {
+            pairs[i].size = 0;
+            pairs[i].dist = 99999;
+        }
+    }
+
+    /* hough transformation */
+    for (i = 0; i < COARSE_SIZE; i++) {
+        for (j = 0; j < pairs[i].size; j++) {
+            for (k = i + 1; k < COARSE_SIZE; k++) {
+                for (l = 0; l < pairs[k].size; l++) {
+                    if (pairs[i].b[j] != pairs[k].b[l]) {
+                        /* linear regression */
+                        m = (pairs[k].b_pos[l]-pairs[i].b_pos[j]) / (k-i); /* good value between 0.0 - 2.0 */
+                        framerate = (int) m*30 + 0.5; /* round up to 0 - 60 */
+                        if (framerate>0 && framerate <= MAX_FRAMERATE) {
+                            offset = pairs[i].b_pos[j] - ((int) m*i + 0.5); /* only second part has to be rounded up */
+                            if (offset > -HOUGH_MAX_OFFSET && offset < HOUGH_MAX_OFFSET) {
+                                if (pairs[i].dist < pairs[k].dist) {
+                                    if (pairs[i].dist < hspace[framerate-1][offset+HOUGH_MAX_OFFSET].dist) {
+                                        hspace[framerate-1][offset+HOUGH_MAX_OFFSET].dist = pairs[i].dist;
+                                        hspace[framerate-1][offset+HOUGH_MAX_OFFSET].a = pairs[i].a;
+                                        hspace[framerate-1][offset+HOUGH_MAX_OFFSET].b = pairs[i].b[j];
+                                    }
+                                } else {
+                                    if (pairs[k].dist < hspace[framerate-1][offset+HOUGH_MAX_OFFSET].dist) {
+                                        hspace[framerate-1][offset+HOUGH_MAX_OFFSET].dist = pairs[k].dist;
+                                        hspace[framerate-1][offset+HOUGH_MAX_OFFSET].a = pairs[k].a;
+                                        hspace[framerate-1][offset+HOUGH_MAX_OFFSET].b = pairs[k].b[l];
+                                    }
+                                }
+
+                                score = hspace[framerate-1][offset+HOUGH_MAX_OFFSET].score + 1;
+                                if (score > hmax )
+                                    hmax = score;
+                                hspace[framerate-1][offset+HOUGH_MAX_OFFSET].score = score;
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    if (hmax > 0) {
+        hmax = (int) (0.7*hmax);
+        for (i = 0; i < MAX_FRAMERATE; i++) {
+            for (j = 0; j < HOUGH_MAX_OFFSET; j++) {
+                if (hmax < hspace[i][j].score) {
+                    if (c == NULL) {
+                        c = av_malloc(sizeof(MatchingInfo));
+                        if (!c)
+                            av_log(ctx, AV_LOG_FATAL, "Could not allocate memory");
+                        cands = c;
+                    } else {
+                        c->next = av_malloc(sizeof(MatchingInfo));
+                        if (!c->next)
+                            av_log(ctx, AV_LOG_FATAL, "Could not allocate memory");
+                        c = c->next;
+                    }
+                    c->framerateratio = (i+1.0) / 30;
+                    c->score = hspace[i][j].score;
+                    c->offset = j-90;
+                    c->first = hspace[i][j].a;
+                    c->second = hspace[i][j].b;
+                    c->next = NULL;
+
+                    /* not used */
+                    c->meandist = 0;
+                    c->matchframes = 0;
+                    c->whole = 0;
+                }
+            }
+        }
+    }
+    for (i = 0; i < MAX_FRAMERATE; i++) {
+        av_freep(&hspace[i]);
+    }
+    av_freep(&hspace);
+    return cands;
+}
+
+static int iterate_frame(double frr, FineSignature **a, FineSignature **b, int fcount, int *bcount, int dir)
+{
+    int step;
+
+    /* between 1 and 2, because frr is between 1 and 2 */
+    step = ((int) 0.5 + fcount     * frr) /* current frame */
+          -((int) 0.5 + (fcount-1) * frr);/* last frame */
+
+    if (dir == DIR_NEXT) {
+        if (frr >= 1.0) {
+            if ((*a)->next) {
+                *a = (*a)->next;
+            } else {
+                return DIR_NEXT_END;
+            }
+
+            if (step == 1) {
+                if ((*b)->next) {
+                    *b = (*b)->next;
+                    (*bcount)++;
+                } else {
+                    return DIR_NEXT_END;
+                }
+            } else {
+                if ((*b)->next && (*b)->next->next) {
+                    *b = (*b)->next->next;
+                    (*bcount)++;
+                } else {
+                    return DIR_NEXT_END;
+                }
+            }
+        } else {
+            if ((*b)->next) {
+                *b = (*b)->next;
+                (*bcount)++;
+            } else {
+                return DIR_NEXT_END;
+            }
+
+            if (step == 1) {
+                if ((*a)->next) {
+                    *a = (*a)->next;
+                } else {
+                    return DIR_NEXT_END;
+                }
+            } else {
+                if ((*a)->next && (*a)->next->next) {
+                    *a = (*a)->next->next;
+                } else {
+                    return DIR_NEXT_END;
+                }
+            }
+        }
+        return DIR_NEXT;
+    } else {
+        if (frr >= 1.0) {
+            if ((*a)->prev) {
+                *a = (*a)->prev;
+            } else {
+                return DIR_PREV_END;
+            }
+
+            if (step == 1) {
+                if ((*b)->prev) {
+                    *b = (*b)->prev;
+                    (*bcount)++;
+                } else {
+                    return DIR_PREV_END;
+                }
+            } else {
+                if ((*b)->prev && (*b)->prev->prev) {
+                    *b = (*b)->prev->prev;
+                    (*bcount)++;
+                } else {
+                    return DIR_PREV_END;
+                }
+            }
+        } else {
+            if ((*b)->prev) {
+                *b = (*b)->prev;
+                (*bcount)++;
+            } else {
+                return DIR_PREV_END;
+            }
+
+            if (step == 1) {
+                if ((*a)->prev) {
+                    *a = (*a)->prev;
+                } else {
+                    return DIR_PREV_END;
+                }
+            } else {
+                if ((*a)->prev && (*a)->prev->prev) {
+                    *a = (*a)->prev->prev;
+                } else {
+                    return DIR_PREV_END;
+                }
+            }
+        }
+        return DIR_PREV;
+    }
+}
+
+static MatchingInfo evaluate_parameters(AVFilterContext *ctx, SignatureContext *sc, MatchingInfo *infos, MatchingInfo bestmatch, int mode)
+{
+    int dist, distsum = 0, bcount = 1, dir = DIR_NEXT;
+    int fcount = 0, goodfcount = 0, gooda = 0, goodb = 0;
+    double meandist, minmeandist = bestmatch.meandist;
+    int tolerancecount = 0;
+    FineSignature *a, *b, *aprev, *bprev;
+    int status = STATUS_NULL;
+
+    for (; infos != NULL; infos = infos->next) {
+        a = infos->first;
+        b = infos->second;
+        while (1) {
+            dist = get_l1dist(ctx, sc, a->framesig, b->framesig);
+
+            if (dist > sc->thl1) {
+                if (a->confidence >= 1 || b->confidence >= 1) {
+                    /* bad frame (because high different information) */
+                    tolerancecount++;
+                }
+
+                if (tolerancecount > 2) {
+                    a = aprev;
+                    b = bprev;
+                    if (dir == DIR_NEXT) {
+                        /* turn around */
+                        a = infos->first;
+                        b = infos->second;
+                        dir = DIR_PREV;
+                    } else {
+                        break;
+                    }
+                }
+            } else {
+                /* good frame */
+                distsum += dist;
+                goodfcount++;
+                tolerancecount=0;
+
+                aprev = a;
+                bprev = b;
+
+                if (a->confidence < 1) gooda++;
+                if (b->confidence < 1) goodb++;
+            }
+
+            fcount++;
+
+            dir = iterate_frame(infos->framerateratio, &a, &b, fcount, &bcount, dir);
+            if (dir == DIR_NEXT_END) {
+                status = STATUS_END_REACHED;
+                a = infos->first;
+                b = infos->second;
+                dir = iterate_frame(infos->framerateratio, &a, &b, fcount, &bcount, DIR_PREV);
+            }
+
+            if (dir == DIR_PREV_END) {
+                status |= STATUS_BEGIN_REACHED;
+                break;
+            }
+
+            if (sc->thdi != 0 && bcount >= sc->thdi) {
+                break; /* enough frames found */
+            }
+        }
+
+        if (bcount < sc->thdi)
+            continue; /* matching sequence is too short */
+        if ((double) goodfcount / (double) fcount < sc->thit)
+            continue;
+        if ((double) goodfcount*0.5 < FFMAX(gooda, goodb))
+            continue;
+
+        meandist = (double) goodfcount / (double) distsum;
+
+        if (meandist < minmeandist ||
+                status == STATUS_END_REACHED | STATUS_BEGIN_REACHED ||
+                mode == MODE_FAST){
+            minmeandist = meandist;
+            /* bestcandidate in this iteration */
+            bestmatch.meandist = meandist;
+            bestmatch.matchframes = bcount;
+            bestmatch.framerateratio = infos->framerateratio;
+            bestmatch.score = infos->score;
+            bestmatch.offset = infos->offset;
+            bestmatch.first = infos->first;
+            bestmatch.second = infos->second;
+            bestmatch.whole = 0; /* will be set to true later */
+            bestmatch.next = NULL;
+        }
+
+        /* whole sequence is automatically best match */
+        if (status == (STATUS_END_REACHED | STATUS_BEGIN_REACHED)) {
+            bestmatch.whole = 1;
+            break;
+        }
+
+        /* first matching sequence is enough, finding the best one is not necessary */
+        if (mode == MODE_FAST) {
+            break;
+        }
+    }
+    return bestmatch;
+}
+
+static void sll_free(MatchingInfo *sll)
+{
+    void *tmp;
+    while (sll) {
+        tmp = sll;
+        sll = sll->next;
+        av_freep(&tmp);
+    }
+}
+
+static MatchingInfo lookup_signatures(AVFilterContext *ctx, SignatureContext *sc, StreamContext *first, StreamContext *second, int mode)
+{
+    CoarseSignature *cs, *cs2;
+    MatchingInfo *infos;
+    MatchingInfo bestmatch;
+    MatchingInfo *i;
+
+    cs = first->coarsesiglist;
+    cs2 = second->coarsesiglist;
+
+    /* score of bestmatch is 0, if no match is found */
+    bestmatch.score = 0;
+    bestmatch.meandist = 99999;
+    bestmatch.whole = 0;
+
+    fill_l1distlut(sc->l1distlut);
+
+    /* stage 1: coarsesignature matching */
+    if (find_next_coarsecandidate(sc, second->coarsesiglist, &cs, &cs2, 1) == 0)
+        return bestmatch; /* no candidate found */
+    do {
+        av_log(ctx, AV_LOG_DEBUG, "Stage 1: got coarsesignature pair. indices of first frame: %d and %d\n", cs->first->index, cs2->first->index);
+        /* stage 2: l1-distance and hough-transform */
+        av_log(ctx, AV_LOG_DEBUG, "Stage 2: calculate matching parameters\n");
+        infos = get_matching_parameters(ctx, sc, cs->first, cs2->first);
+        if (av_log_get_level() == AV_LOG_DEBUG) {
+            for (i = infos; i != NULL; i = i->next) {
+                av_log(ctx, AV_LOG_DEBUG, "Stage 2: matching pair at %d and %d, ratio %f, offset %d\n", i->first->index, i->second->index, i->framerateratio, i->offset);
+            }
+        }
+        /* stage 3: evaluation */
+        av_log(ctx, AV_LOG_DEBUG, "Stage 3: evaluate\n");
+        if (infos) {
+            bestmatch = evaluate_parameters(ctx, sc, infos, bestmatch, mode);
+            av_log(ctx, AV_LOG_DEBUG, "Stage 3: best matching pair at %d and %d, ratio %f, offset %d, score %d, %d frames matching\n", bestmatch.first->index, bestmatch.second->index, bestmatch.framerateratio, bestmatch.offset, bestmatch.score, bestmatch.matchframes);
+            sll_free(infos);
+        }
+    } while (find_next_coarsecandidate(sc, second->coarsesiglist, &cs, &cs2, 0) && !bestmatch.whole);
+    return bestmatch;
+
+}
diff --git a/libavfilter/version.h b/libavfilter/version.h
index c2684bfe94..a61ca32712 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   6
-#define LIBAVFILTER_VERSION_MINOR  77
+#define LIBAVFILTER_VERSION_MINOR  78
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
diff --git a/libavfilter/vf_signature.c b/libavfilter/vf_signature.c
new file mode 100644
index 0000000000..57cb96b6c4
--- /dev/null
+++ b/libavfilter/vf_signature.c
@@ -0,0 +1,767 @@
+/*
+ * Copyright (c) 2017 Gerion Entrup
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with FFmpeg; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/**
+ * @file
+ * MPEG-7 video signature calculation and lookup filter
+ * @see http://epubs.surrey.ac.uk/531590/1/MPEG-7%20Video%20Signature%20Author%27s%20Copy.pdf
+ */
+
+#include <float.h>
+#include "libavcodec/put_bits.h"
+#include "libavformat/avformat.h"
+#include "libavutil/opt.h"
+#include "libavutil/avstring.h"
+#include "libavutil/intreadwrite.h"
+#include "libavutil/timestamp.h"
+#include "avfilter.h"
+#include "internal.h"
+#include "signature.h"
+#include "signature_lookup.c"
+
+#define OFFSET(x) offsetof(SignatureContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_VIDEO_PARAM
+#define BLOCK_LCM (int64_t) 476985600
+
+static const AVOption signature_options[] = {
+    { "detectmode", "set the detectmode",
+        OFFSET(mode),         AV_OPT_TYPE_INT,    {.i64 = MODE_OFF}, 0, NB_LOOKUP_MODE-1, FLAGS, "mode" },
+        { "off",  NULL, 0, AV_OPT_TYPE_CONST, {.i64 = MODE_OFF},  0, 0, .flags = FLAGS, "mode" },
+        { "full", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = MODE_FULL}, 0, 0, .flags = FLAGS, "mode" },
+        { "fast", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = MODE_FAST}, 0, 0, .flags = FLAGS, "mode" },
+    { "nb_inputs",  "number of inputs",
+        OFFSET(nb_inputs),    AV_OPT_TYPE_INT,    {.i64 = 1},        1, INT_MAX,          FLAGS },
+    { "filename",   "filename for output files",
+        OFFSET(filename),     AV_OPT_TYPE_STRING, {.str = ""},       0, NB_FORMATS-1,     FLAGS },
+    { "format",     "set output format",
+        OFFSET(format),       AV_OPT_TYPE_INT,    {.i64 = FORMAT_BINARY}, 0, 1,           FLAGS , "format" },
+        { "binary", 0, 0, AV_OPT_TYPE_CONST, {.i64=FORMAT_BINARY}, 0, 0, FLAGS, "format" },
+        { "xml",    0, 0, AV_OPT_TYPE_CONST, {.i64=FORMAT_XML},    0, 0, FLAGS, "format" },
+    { "th_d",       "threshold to detect one word as similar",
+        OFFSET(thworddist),   AV_OPT_TYPE_INT,    {.i64 = 9000},     1, INT_MAX,          FLAGS },
+    { "th_dc",      "threshold to detect all words as similar",
+        OFFSET(thcomposdist), AV_OPT_TYPE_INT,    {.i64 = 60000},    1, INT_MAX,          FLAGS },
+    { "th_xh",      "threshold to detect frames as similar",
+        OFFSET(thl1),         AV_OPT_TYPE_INT,    {.i64 = 116},      1, INT_MAX,          FLAGS },
+    { "th_di",      "minimum length of matching sequence in frames",
+        OFFSET(thdi),         AV_OPT_TYPE_INT,    {.i64 = 0},        0, INT_MAX,          FLAGS },
+    { "th_it",      "threshold for relation of good to all frames",
+        OFFSET(thit),         AV_OPT_TYPE_DOUBLE, {.dbl = 0.5},    0.0, 1.0,              FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(signature);
+
+static int query_formats(AVFilterContext *ctx)
+{
+    /* all formats with a seperate gray value */
+    static const enum AVPixelFormat pix_fmts[] = {
+        AV_PIX_FMT_GRAY8,
+        AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUV411P,
+        AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV422P,
+        AV_PIX_FMT_YUV440P, AV_PIX_FMT_YUV444P,
+        AV_PIX_FMT_YUVJ411P, AV_PIX_FMT_YUVJ420P,
+        AV_PIX_FMT_YUVJ422P, AV_PIX_FMT_YUVJ444P,
+        AV_PIX_FMT_YUVJ440P,
+        AV_PIX_FMT_NV12, AV_PIX_FMT_NV21,
+        AV_PIX_FMT_NONE
+    };
+
+    return ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    SignatureContext *sic = ctx->priv;
+    StreamContext *sc = &(sic->streamcontexts[FF_INLINK_IDX(inlink)]);
+
+    sc->time_base = inlink->time_base;
+    /* test for overflow */
+    sc->divide = (((uint64_t) inlink->w/32) * (inlink->w/32 + 1) * (inlink->h/32 * inlink->h/32 + 1) > INT64_MAX / (BLOCK_LCM * 255));
+    if (sc->divide) {
+        av_log(ctx, AV_LOG_WARNING, "Input dimension too high for precise calculation, numbers will be rounded.\n");
+    }
+    sc->w = inlink->w;
+    sc->h = inlink->h;
+    return 0;
+}
+
+static int get_block_size(const Block *b)
+{
+    return (b->to.y - b->up.y + 1) * (b->to.x - b->up.x + 1);
+}
+
+static uint64_t get_block_sum(StreamContext *sc, uint64_t intpic[32][32], const Block *b)
+{
+    uint64_t sum = 0;
+
+    int x0, y0, x1, y1;
+
+    x0 = b->up.x;
+    y0 = b->up.y;
+    x1 = b->to.x;
+    y1 = b->to.y;
+
+    if (x0-1 >= 0 && y0-1 >= 0) {
+        sum = intpic[y1][x1] + intpic[y0-1][x0-1] - intpic[y1][x0-1] - intpic[y0-1][x1];
+    } else if (x0-1 >= 0) {
+        sum = intpic[y1][x1] - intpic[y1][x0-1];
+    } else if (y0-1 >= 0) {
+        sum = intpic[y1][x1] - intpic[y0-1][x1];
+    } else {
+        sum = intpic[y1][x1];
+    }
+    return sum;
+}
+
+static int cmp(const uint64_t *a, const uint64_t *b)
+{
+    return *a < *b ? -1 : ( *a > *b ? 1 : 0 );
+}
+
+/**
+ * sets the bit at position pos to 1 in data
+ */
+static void set_bit(uint8_t* data, size_t pos)
+{
+    uint8_t mask = 1 << 7-(pos%8);
+    data[pos/8] |= mask;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *picref)
+{
+    AVFilterContext *ctx = inlink->dst;
+    SignatureContext *sic = ctx->priv;
+    StreamContext *sc = &(sic->streamcontexts[FF_INLINK_IDX(inlink)]);
+    FineSignature* fs;
+
+    static const uint8_t pot3[5] = { 3*3*3*3, 3*3*3, 3*3, 3, 1 };
+    /* indexes of words : 210,217,219,274,334  44,175,233,270,273  57,70,103,237,269  100,285,295,337,354  101,102,111,275,296
+    s2usw = sorted to unsorted wordvec: 44 is at index 5, 57 at index 10...
+    */
+    static const unsigned int wordvec[25] = {44,57,70,100,101,102,103,111,175,210,217,219,233,237,269,270,273,274,275,285,295,296,334,337,354};
+    static const uint8_t      s2usw[25]   = { 5,10,11, 15, 20, 21, 12, 22,  6,  0,  1,  2,  7, 13, 14,  8,  9,  3, 23, 16, 17, 24,  4, 18, 19};
+
+    uint8_t wordt2b[5] = { 0, 0, 0, 0, 0 }; /* word ternary to binary */
+    uint64_t intpic[32][32];
+    uint64_t rowcount;
+    uint8_t *p = picref->data[0];
+    int inti, intj;
+    int *intjlut;
+
+    uint64_t conflist[DIFFELEM_SIZE];
+    int f = 0, g = 0, w = 0;
+    int32_t dh1 = 1, dh2 = 1, dw1 = 1, dw2 = 1, a, b;
+    int64_t denom;
+    int i, j, k, ternary;
+    uint64_t blocksum;
+    int blocksize;
+    int64_t th; /* threshold */
+    int64_t sum;
+
+    int64_t precfactor = (sc->divide) ? 65536 : BLOCK_LCM;
+
+    /* initialize fs */
+    if (sc->curfinesig) {
+        fs = av_mallocz(sizeof(FineSignature));
+        if (!fs)
+            return AVERROR(ENOMEM);
+        sc->curfinesig->next = fs;
+        fs->prev = sc->curfinesig;
+        sc->curfinesig = fs;
+    } else {
+        fs = sc->curfinesig = sc->finesiglist;
+        sc->curcoarsesig1->first = fs;
+    }
+
+    fs->pts = picref->pts;
+    fs->index = sc->lastindex++;
+
+    memset(intpic, 0, sizeof(uint64_t)*32*32);
+    intjlut = av_malloc_array(inlink->w, sizeof(int));
+    if (!intjlut)
+        return AVERROR(ENOMEM);
+    for (i = 0; i < inlink->w; i++) {
+        intjlut[i] = (i*32)/inlink->w;
+    }
+
+    for (i = 0; i < inlink->h; i++) {
+        inti = (i*32)/inlink->h;
+        for (j = 0; j < inlink->w; j++) {
+            intj = intjlut[j];
+            intpic[inti][intj] += p[j];
+        }
+        p += picref->linesize[0];
+    }
+    av_freep(&intjlut);
+
+    /* The following calculates a summed area table (intpic) and brings the numbers
+     * in intpic to the same denominator.
+     * So you only have to handle the numinator in the following sections.
+     */
+    dh1 = inlink->h / 32;
+    if (inlink->h % 32)
+        dh2 = dh1 + 1;
+    dw1 = inlink->w / 32;
+    if (inlink->w % 32)
+        dw2 = dw1 + 1;
+    denom = (sc->divide) ? dh1 * dh2 * dw1 * dw2 : 1;
+
+    for (i = 0; i < 32; i++) {
+        rowcount = 0;
+        a = 1;
+        if (dh2 > 1) {
+            a = ((inlink->h*(i+1))%32 == 0) ? (inlink->h*(i+1))/32 - 1 : (inlink->h*(i+1))/32;
+            a -= ((inlink->h*i)%32 == 0) ? (inlink->h*i)/32 - 1 : (inlink->h*i)/32;
+            a = (a == dh1)? dh2 : dh1;
+        }
+        for (j = 0; j < 32; j++) {
+            b = 1;
+            if (dw2 > 1) {
+                b = ((inlink->w*(j+1))%32 == 0) ? (inlink->w*(j+1))/32 - 1 : (inlink->w*(j+1))/32;
+                b -= ((inlink->w*j)%32 == 0) ? (inlink->w*j)/32 - 1 : (inlink->w*j)/32;
+                b = (b == dw1)? dw2 : dw1;
+            }
+            rowcount += intpic[i][j] * a * b * precfactor / denom;
+            if (i > 0) {
+                intpic[i][j] = intpic[i-1][j] + rowcount;
+            } else {
+                intpic[i][j] = rowcount;
+            }
+        }
+    }
+
+    denom = (sc->divide) ? 1 : dh1 * dh2 * dw1 * dw2;
+
+    for (i = 0; i < ELEMENT_COUNT; i++) {
+        const ElemCat* elemcat = elements[i];
+        int64_t* elemsignature;
+        uint64_t* sortsignature;
+
+        elemsignature = av_malloc_array(elemcat->elem_count, sizeof(int64_t));
+        if (!elemsignature)
+            return AVERROR(ENOMEM);
+        sortsignature = av_malloc_array(elemcat->elem_count, sizeof(int64_t));
+        if (!sortsignature)
+            return AVERROR(ENOMEM);
+
+        for (j = 0; j < elemcat->elem_count; j++) {
+            blocksum = 0;
+            blocksize = 0;
+            for (k = 0; k < elemcat->left_count; k++) {
+                blocksum += get_block_sum(sc, intpic, &elemcat->blocks[j*elemcat->block_count+k]);
+                blocksize += get_block_size(&elemcat->blocks[j*elemcat->block_count+k]);
+            }
+            sum = blocksum / blocksize;
+            if (elemcat->av_elem) {
+                sum -= 128 * precfactor * denom;
+            } else {
+                blocksum = 0;
+                blocksize = 0;
+                for (; k < elemcat->block_count; k++) {
+                    blocksum += get_block_sum(sc, intpic, &elemcat->blocks[j*elemcat->block_count+k]);
+                    blocksize += get_block_size(&elemcat->blocks[j*elemcat->block_count+k]);
+                }
+                sum -= blocksum / blocksize;
+                conflist[g++] = FFABS(sum * 8 / (precfactor * denom));
+            }
+
+            elemsignature[j] = sum;
+            sortsignature[j] = FFABS(sum);
+        }
+
+        /* get threshold */
+        qsort(sortsignature, elemcat->elem_count, sizeof(uint64_t), (void*) cmp);
+        th = sortsignature[(int) (elemcat->elem_count*0.333)];
+
+        /* ternarize */
+        for (j = 0; j < elemcat->elem_count; j++) {
+            if (elemsignature[j] < -th) {
+                ternary = 0;
+            } else if (elemsignature[j] <= th) {
+                ternary = 1;
+            } else {
+                ternary = 2;
+            }
+            fs->framesig[f/5] += ternary * pot3[f%5];
+
+            if (f == wordvec[w]) {
+                fs->words[s2usw[w]/5] += ternary * pot3[wordt2b[s2usw[w]/5]++];
+                if (w < 24)
+                    w++;
+            }
+            f++;
+        }
+        av_freep(&elemsignature);
+        av_freep(&sortsignature);
+    }
+
+    /* confidence */
+    qsort(conflist, DIFFELEM_SIZE, sizeof(uint64_t), (void*) cmp);
+    fs->confidence = FFMIN(conflist[DIFFELEM_SIZE/2], 255);
+
+    /* coarsesignature */
+    if (sc->coarsecount == 0) {
+        if (sc->curcoarsesig2) {
+            sc->curcoarsesig1 = av_mallocz(sizeof(CoarseSignature));
+            if (!sc->curcoarsesig1)
+                return AVERROR(ENOMEM);
+            sc->curcoarsesig1->first = fs;
+            sc->curcoarsesig2->next = sc->curcoarsesig1;
+            sc->coarseend = sc->curcoarsesig1;
+        }
+    }
+    if (sc->coarsecount == 45) {
+        sc->midcoarse = 1;
+        sc->curcoarsesig2 = av_mallocz(sizeof(CoarseSignature));
+        if (!sc->curcoarsesig2)
+            return AVERROR(ENOMEM);
+        sc->curcoarsesig2->first = fs;
+        sc->curcoarsesig1->next = sc->curcoarsesig2;
+        sc->coarseend = sc->curcoarsesig2;
+    }
+    for (i = 0; i < 5; i++) {
+        set_bit(sc->curcoarsesig1->data[i], fs->words[i]);
+    }
+    /* assuming the actual frame is the last */
+    sc->curcoarsesig1->last = fs;
+    if (sc->midcoarse) {
+        for (i = 0; i < 5; i++) {
+            set_bit(sc->curcoarsesig2->data[i], fs->words[i]);
+        }
+        sc->curcoarsesig2->last = fs;
+    }
+
+    sc->coarsecount = (sc->coarsecount+1)%90;
+
+    /* debug printing finesignature */
+    if (av_log_get_level() == AV_LOG_DEBUG) {
+        av_log(ctx, AV_LOG_DEBUG, "input %d, confidence: %d\n", FF_INLINK_IDX(inlink), fs->confidence);
+
+        av_log(ctx, AV_LOG_DEBUG, "words:");
+        for (i = 0; i < 5; i++) {
+            av_log(ctx, AV_LOG_DEBUG, " %d:", fs->words[i] );
+            av_log(ctx, AV_LOG_DEBUG, " %d", fs->words[i] / pot3[0] );
+            for (j = 1; j < 5; j++)
+                av_log(ctx, AV_LOG_DEBUG, ",%d", fs->words[i] % pot3[j-1] / pot3[j] );
+            av_log(ctx, AV_LOG_DEBUG, ";");
+        }
+        av_log(ctx, AV_LOG_DEBUG, "\n");
+
+        av_log(ctx, AV_LOG_DEBUG, "framesignature:");
+        for (i = 0; i < SIGELEM_SIZE/5; i++) {
+            av_log(ctx, AV_LOG_DEBUG, " %d", fs->framesig[i] / pot3[0] );
+            for (j = 1; j < 5; j++)
+                av_log(ctx, AV_LOG_DEBUG, ",%d", fs->framesig[i] % pot3[j-1] / pot3[j] );
+        }
+        av_log(ctx, AV_LOG_DEBUG, "\n");
+    }
+
+    if (FF_INLINK_IDX(inlink) == 0)
+        return ff_filter_frame(inlink->dst->outputs[0], picref);
+    return 1;
+}
+
+static int xml_export(AVFilterContext *ctx, StreamContext *sc, const char* filename)
+{
+    FineSignature* fs;
+    CoarseSignature* cs;
+    int i, j;
+    FILE* f;
+    unsigned int pot3[5] = { 3*3*3*3, 3*3*3, 3*3, 3, 1 };
+
+    f = fopen(filename, "w");
+    if (!f) {
+        int err = AVERROR(EINVAL);
+        char buf[128];
+        av_strerror(err, buf, sizeof(buf));
+        av_log(ctx, AV_LOG_ERROR, "cannot open xml file %s: %s\n", filename, buf);
+        return err;
+    }
+
+    /* header */
+    fprintf(f, "<?xml version='1.0' encoding='ASCII' ?>\n");
+    fprintf(f, "<Mpeg7 xmlns=\"urn:mpeg:mpeg7:schema:2001\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:schemaLocation=\"urn:mpeg:mpeg7:schema:2001 schema/Mpeg7-2001.xsd\">\n");
+    fprintf(f, "  <DescriptionUnit xsi:type=\"DescriptorCollectionType\">\n");
+    fprintf(f, "    <Descriptor xsi:type=\"VideoSignatureType\">\n");
+    fprintf(f, "      <VideoSignatureRegion>\n");
+    fprintf(f, "        <VideoSignatureSpatialRegion>\n");
+    fprintf(f, "          <Pixel>0 0 </Pixel>\n");
+    fprintf(f, "          <Pixel>%d %d </Pixel>\n", sc->w - 1, sc->h - 1);
+    fprintf(f, "        </VideoSignatureSpatialRegion>\n");
+    fprintf(f, "        <StartFrameOfSpatialRegion>0</StartFrameOfSpatialRegion>\n");
+    /* hoping num is 1, other values are vague */
+    fprintf(f, "        <MediaTimeUnit>%d</MediaTimeUnit>\n", sc->time_base.den / sc->time_base.num);
+    fprintf(f, "        <MediaTimeOfSpatialRegion>\n");
+    fprintf(f, "          <StartMediaTimeOfSpatialRegion>0</StartMediaTimeOfSpatialRegion>\n");
+    fprintf(f, "          <EndMediaTimeOfSpatialRegion>%" PRIu64 "</EndMediaTimeOfSpatialRegion>\n", sc->coarseend->last->pts);
+    fprintf(f, "        </MediaTimeOfSpatialRegion>\n");
+
+    /* coarsesignatures */
+    for (cs = sc->coarsesiglist; cs; cs = cs->next) {
+        fprintf(f, "        <VSVideoSegment>\n");
+        fprintf(f, "          <StartFrameOfSegment>%" PRIu32 "</StartFrameOfSegment>\n", cs->first->index);
+        fprintf(f, "          <EndFrameOfSegment>%" PRIu32 "</EndFrameOfSegment>\n", cs->last->index);
+        fprintf(f, "          <MediaTimeOfSegment>\n");
+        fprintf(f, "            <StartMediaTimeOfSegment>%" PRIu64 "</StartMediaTimeOfSegment>\n", cs->first->pts);
+        fprintf(f, "            <EndMediaTimeOfSegment>%" PRIu64 "</EndMediaTimeOfSegment>\n", cs->last->pts);
+        fprintf(f, "          </MediaTimeOfSegment>\n");
+        for (i = 0; i < 5; i++) {
+            fprintf(f, "          <BagOfWords>");
+            for (j = 0; j < 31; j++) {
+                uint8_t n = cs->data[i][j];
+                if (j < 30) {
+                    fprintf(f, "%d  %d  %d  %d  %d  %d  %d  %d  ", (n & 0x80) >> 7,
+                                                                   (n & 0x40) >> 6,
+                                                                   (n & 0x20) >> 5,
+                                                                   (n & 0x10) >> 4,
+                                                                   (n & 0x08) >> 3,
+                                                                   (n & 0x04) >> 2,
+                                                                   (n & 0x02) >> 1,
+                                                                   (n & 0x01));
+                } else {
+                    /* print only 3 bit in last byte */
+                    fprintf(f, "%d  %d  %d ", (n & 0x80) >> 7,
+                                              (n & 0x40) >> 6,
+                                              (n & 0x20) >> 5);
+                }
+            }
+            fprintf(f, "</BagOfWords>\n");
+        }
+        fprintf(f, "        </VSVideoSegment>\n");
+    }
+
+    /* finesignatures */
+    for (fs = sc->finesiglist; fs; fs = fs->next) {
+        fprintf(f, "        <VideoFrame>\n");
+        fprintf(f, "          <MediaTimeOfFrame>%" PRIu64 "</MediaTimeOfFrame>\n", fs->pts);
+        /* confidence */
+        fprintf(f, "          <FrameConfidence>%d</FrameConfidence>\n", fs->confidence);
+        /* words */
+        fprintf(f, "          <Word>");
+        for (i = 0; i < 5; i++) {
+            fprintf(f, "%d ", fs->words[i]);
+            if (i < 4) {
+                fprintf(f, " ");
+            }
+        }
+        fprintf(f, "</Word>\n");
+        /* framesignature */
+        fprintf(f, "          <FrameSignature>");
+        for (i = 0; i< SIGELEM_SIZE/5; i++) {
+            if (i > 0) {
+                fprintf(f, " ");
+            }
+            fprintf(f, "%d ", fs->framesig[i] / pot3[0]);
+            for (j = 1; j < 5; j++)
+                fprintf(f, " %d ", fs->framesig[i] % pot3[j-1] / pot3[j] );
+        }
+        fprintf(f, "</FrameSignature>\n");
+        fprintf(f, "        </VideoFrame>\n");
+    }
+    fprintf(f, "      </VideoSignatureRegion>\n");
+    fprintf(f, "    </Descriptor>\n");
+    fprintf(f, "  </DescriptionUnit>\n");
+    fprintf(f, "</Mpeg7>\n");
+
+    fclose(f);
+    return 0;
+}
+
+static int binary_export(AVFilterContext *ctx, StreamContext *sc, const char* filename)
+{
+    FILE* f;
+    FineSignature* fs;
+    CoarseSignature* cs;
+    uint32_t numofsegments = (sc->lastindex + 44)/45;
+    int i, j;
+    PutBitContext buf;
+    /* buffer + header + coarsesignatures + finesignature */
+    int len = (512 + 6 * 32 + 3*16 + 2 +
+        numofsegments * (4*32 + 1 + 5*243) +
+        sc->lastindex * (2 + 32 + 6*8 + 608)) / 8;
+    uint8_t* buffer = av_malloc_array(len, sizeof(uint8_t));
+    if (!buffer)
+        return AVERROR(ENOMEM);
+
+    f = fopen(filename, "wb");
+    if (!f) {
+        int err = AVERROR(EINVAL);
+        char buf[128];
+        av_strerror(err, buf, sizeof(buf));
+        av_log(ctx, AV_LOG_ERROR, "cannot open file %s: %s\n", filename, buf);
+        return err;
+    }
+    init_put_bits(&buf, buffer, len);
+
+    put_bits32(&buf, 1); /* NumOfSpatial Regions, only 1 supported */
+    put_bits(&buf, 1, 1); /* SpatialLocationFlag, always the whole image */
+    put_bits32(&buf, 0); /* PixelX,1 PixelY,1, 0,0 */
+    put_bits(&buf, 16, sc->w-1 & 0xFFFF); /* PixelX,2 */
+    put_bits(&buf, 16, sc->h-1 & 0xFFFF); /* PixelY,2 */
+    put_bits32(&buf, 0); /* StartFrameOfSpatialRegion */
+    put_bits32(&buf, sc->lastindex); /* NumOfFrames */
+    /* hoping num is 1, other values are vague */
+    /* den/num might be greater than 16 bit, so cutting it */
+    put_bits(&buf, 16, 0xFFFF & (sc->time_base.den / sc->time_base.num)); /* MediaTimeUnit */
+    put_bits(&buf, 1, 1); /* MediaTimeFlagOfSpatialRegion */
+    put_bits32(&buf, 0); /* StartMediaTimeOfSpatialRegion */
+    put_bits32(&buf, 0xFFFFFFFF & sc->coarseend->last->pts); /* EndMediaTimeOfSpatialRegion */
+    put_bits32(&buf, numofsegments); /* NumOfSegments */
+    /* coarsesignatures */
+    for (cs = sc->coarsesiglist; cs; cs = cs->next) {
+        put_bits32(&buf, cs->first->index); /* StartFrameOfSegment */
+        put_bits32(&buf, cs->last->index); /* EndFrameOfSegment */
+        put_bits(&buf, 1, 1); /* MediaTimeFlagOfSegment */
+        put_bits32(&buf, 0xFFFFFFFF & cs->first->pts); /* StartMediaTimeOfSegment */
+        put_bits32(&buf, 0xFFFFFFFF & cs->last->pts); /* EndMediaTimeOfSegment */
+        for (i = 0; i < 5; i++) {
+            /* put 243 bits ( = 7 * 32 + 19 = 8 * 28 + 19) into buffer */
+            for (j = 0; j < 30; j++) {
+                put_bits(&buf, 8, cs->data[i][j]);
+            }
+            put_bits(&buf, 3, cs->data[i][30] >> 5);
+        }
+    }
+    /* finesignatures */
+    put_bits(&buf, 1, 0); /* CompressionFlag, only 0 supported */
+    for (fs = sc->finesiglist; fs; fs = fs->next) {
+        put_bits(&buf, 1, 1); /* MediaTimeFlagOfFrame */
+        put_bits32(&buf, 0xFFFFFFFF & fs->pts); /* MediaTimeOfFrame */
+        put_bits(&buf, 8, fs->confidence); /* FrameConfidence */
+        for (i = 0; i < 5; i++) {
+            put_bits(&buf, 8, fs->words[i]); /* Words */
+        }
+        /* framesignature */
+        for (i = 0; i < SIGELEM_SIZE/5; i++) {
+            put_bits(&buf, 8, fs->framesig[i]);
+        }
+    }
+
+    avpriv_align_put_bits(&buf);
+    flush_put_bits(&buf);
+    fwrite(buffer, 1, put_bits_count(&buf)/8, f);
+    fclose(f);
+    av_freep(&buffer);
+    return 0;
+}
+
+static int export(AVFilterContext *ctx, StreamContext *sc, int input)
+{
+    SignatureContext* sic = ctx->priv;
+    char filename[1024];
+
+    if (sic->nb_inputs > 1) {
+        /* error already handled */
+        av_assert0(av_get_frame_filename(filename, sizeof(filename), sic->filename, input) == 0);
+    } else {
+        strcpy(filename, sic->filename);
+    }
+    if (sic->format == FORMAT_XML) {
+        return xml_export(ctx, sc, filename);
+    } else {
+        return binary_export(ctx, sc, filename);
+    }
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    SignatureContext *sic = ctx->priv;
+    StreamContext *sc, *sc2;
+    MatchingInfo match;
+    int i, j, ret;
+    int lookup = 1; /* indicates wheather EOF of all files is reached */
+
+    /* process all inputs */
+    for (i = 0; i < sic->nb_inputs; i++){
+        sc = &(sic->streamcontexts[i]);
+
+        ret = ff_request_frame(ctx->inputs[i]);
+
+        /* return if unexpected error occurs in input stream */
+        if (ret < 0 && ret != AVERROR_EOF)
+            return ret;
+
+        /* export signature at EOF */
+        if (ret == AVERROR_EOF && !sc->exported) {
+            /* export if wanted */
+            if (strlen(sic->filename) > 0) {
+                if (export(ctx, sc, i) < 0)
+                    return ret;
+            }
+            sc->exported = 1;
+        }
+        lookup &= sc->exported;
+    }
+
+    /* signature lookup */
+    if (lookup && sic->mode != MODE_OFF) {
+        /* iterate over every pair */
+        for (i = 0; i < sic->nb_inputs; i++) {
+            sc = &(sic->streamcontexts[i]);
+            for (j = i+1; j < sic->nb_inputs; j++) {
+                sc2 = &(sic->streamcontexts[j]);
+                match = lookup_signatures(ctx, sic, sc, sc2, sic->mode);
+                if (match.score != 0) {
+                    av_log(ctx, AV_LOG_INFO, "matching of video %d at %f and %d at %f, %d frames matching\n",
+                            i, ((double) match.first->pts * sc->time_base.num) / sc->time_base.den,
+                            j, ((double) match.second->pts * sc2->time_base.num) / sc2->time_base.den,
+                            match.matchframes);
+                    if (match.whole)
+                        av_log(ctx, AV_LOG_INFO, "whole video matching\n");
+                } else {
+                    av_log(ctx, AV_LOG_INFO, "no matching of video %d and %d\n", i, j);
+                }
+            }
+        }
+    }
+
+    return ret;
+}
+
+static av_cold int init(AVFilterContext *ctx)
+{
+
+    SignatureContext *sic = ctx->priv;
+    StreamContext *sc;
+    int i, ret;
+    char tmp[1024];
+
+    sic->streamcontexts = av_mallocz(sic->nb_inputs * sizeof(StreamContext));
+    if (!sic->streamcontexts)
+        return AVERROR(ENOMEM);
+
+    for (i = 0; i < sic->nb_inputs; i++) {
+        AVFilterPad pad = {
+            .type = AVMEDIA_TYPE_VIDEO,
+            .name = av_asprintf("in%d", i),
+            .config_props = config_input,
+            .filter_frame = filter_frame,
+        };
+
+        if (!pad.name)
+            return AVERROR(ENOMEM);
+
+        sc = &(sic->streamcontexts[i]);
+
+        sc->lastindex = 0;
+        sc->finesiglist = av_mallocz(sizeof(FineSignature));
+        if (!sc->finesiglist)
+            return AVERROR(ENOMEM);
+        sc->curfinesig = NULL;
+
+        sc->coarsesiglist = av_mallocz(sizeof(CoarseSignature));
+        if (!sc->coarsesiglist)
+            return AVERROR(ENOMEM);
+        sc->curcoarsesig1 = sc->coarsesiglist;
+        sc->coarseend = sc->coarsesiglist;
+        sc->coarsecount = 0;
+        sc->midcoarse = 0;
+
+        if ((ret = ff_insert_inpad(ctx, i, &pad)) < 0) {
+            av_freep(&pad.name);
+            return ret;
+        }
+    }
+
+    /* check filename */
+    if (sic->nb_inputs > 1 && strlen(sic->filename) > 0 && av_get_frame_filename(tmp, sizeof(tmp), sic->filename, 0) == -1) {
+        av_log(ctx, AV_LOG_ERROR, "The filename must contain %%d or %%0nd, if you have more than one input.\n");
+        return AVERROR(EINVAL);
+    }
+
+    return 0;
+}
+
+
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    SignatureContext *sic = ctx->priv;
+    StreamContext *sc;
+    void* tmp;
+    FineSignature* finsig;
+    CoarseSignature* cousig;
+    int i;
+
+
+    /* free the lists */
+    if (sic->streamcontexts != NULL) {
+        for (i = 0; i < sic->nb_inputs; i++) {
+            sc = &(sic->streamcontexts[i]);
+            finsig = sc->finesiglist;
+            cousig = sc->coarsesiglist;
+
+            while (finsig) {
+                tmp = finsig;
+                finsig = finsig->next;
+                av_freep(&tmp);
+            }
+            sc->finesiglist = NULL;
+
+            while (cousig) {
+                tmp = cousig;
+                cousig = cousig->next;
+                av_freep(&tmp);
+            }
+            sc->coarsesiglist = NULL;
+        }
+        av_freep(&sic->streamcontexts);
+    }
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    AVFilterLink *inlink = ctx->inputs[0];
+
+    outlink->time_base = inlink->time_base;
+    outlink->frame_rate = inlink->frame_rate;
+    outlink->sample_aspect_ratio = inlink->sample_aspect_ratio;
+    outlink->w = inlink->w;
+    outlink->h = inlink->h;
+
+    return 0;
+}
+
+static const AVFilterPad signature_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .request_frame = request_frame,
+        .config_props  = config_output,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_signature = {
+    .name          = "signature",
+    .description   = NULL_IF_CONFIG_SMALL("Calculate the MPEG-7 video signature"),
+    .priv_size     = sizeof(SignatureContext),
+    .priv_class    = &signature_class,
+    .init          = init,
+    .uninit        = uninit,
+    .query_formats = query_formats,
+    .outputs       = signature_outputs,
+    .inputs        = NULL,
+    .flags         = AVFILTER_FLAG_DYNAMIC_INPUTS,
+};