From 844ff494696e75221e718278139a0db5766ae797 Mon Sep 17 00:00:00 2001
From: Kieran Kunhya <kieran@kunhya.com>
Date: Sun, 19 Aug 2018 02:31:42 +0100
Subject: mpeg4video: Add Studio DPCM support

---
 libavcodec/mpeg4videodec.c | 91 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 88 insertions(+), 3 deletions(-)

(limited to 'libavcodec/mpeg4videodec.c')

diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
index 1686ed1001..4c77081237 100644
--- a/libavcodec/mpeg4videodec.c
+++ b/libavcodec/mpeg4videodec.c
@@ -24,6 +24,7 @@
 
 #include "libavutil/internal.h"
 #include "libavutil/opt.h"
+#include "libavutil/pixdesc.h"
 #include "error_resilience.h"
 #include "hwaccel.h"
 #include "idctdsp.h"
@@ -36,6 +37,7 @@
 #include "profiles.h"
 #include "thread.h"
 #include "xvididct.h"
+#include "unary.h"
 
 /* The defines below define the number of bits that are read at once for
  * reading vlc values. Changing these may improve speed and data cache needs
@@ -1923,10 +1925,91 @@ static int mpeg4_decode_studio_block(MpegEncContext *s, int32_t block[64], int n
     return 0;
 }
 
+static int mpeg4_decode_dpcm_macroblock(MpegEncContext *s, int16_t macroblock[256], int n)
+{
+    int i, j, w, h, idx = 0;
+    int block_mean, rice_parameter, rice_prefix_code, rice_suffix_code,
+        dpcm_residual, left, top, topleft, min_left_top, max_left_top, p, p2, output;
+    h = 16 >> (n ? s->chroma_y_shift : 0);
+    w = 16 >> (n ? s->chroma_x_shift : 0);
+
+    block_mean = get_bits(&s->gb, s->avctx->bits_per_raw_sample);
+    if (block_mean == 0){
+        av_log(s->avctx, AV_LOG_ERROR, "Forbidden block_mean\n");
+        return AVERROR_INVALIDDATA;
+    }
+    s->last_dc[n] = block_mean * (1 << (s->dct_precision + s->intra_dc_precision));
+
+    rice_parameter = get_bits(&s->gb, 4);
+    if (rice_parameter == 0) {
+        av_log(s->avctx, AV_LOG_ERROR, "Forbidden rice_parameter\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (rice_parameter == 15)
+        rice_parameter = 0;
+
+    if (rice_parameter > 11) {
+        av_log(s->avctx, AV_LOG_ERROR, "Forbidden rice_parameter\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    for (i = 0; i < h; i++) {
+        output = 1 << (s->avctx->bits_per_raw_sample - 1);
+        top = 1 << (s->avctx->bits_per_raw_sample - 1);
+
+        for (j = 0; j < w; j++) {
+            left = output;
+            topleft = top;
+
+            rice_prefix_code = get_unary(&s->gb, 1, 12);
+
+            /* Escape */
+            if (rice_prefix_code == 11)
+                dpcm_residual = get_bits(&s->gb, s->avctx->bits_per_raw_sample);
+            else {
+                rice_suffix_code = get_bitsz(&s->gb, rice_parameter);
+                dpcm_residual = (rice_prefix_code << rice_parameter) + rice_suffix_code;
+            }
+
+            /* Map to a signed residual */
+            if (dpcm_residual & 1)
+                dpcm_residual = (-1 * dpcm_residual) >> 1;
+            else
+                dpcm_residual = (dpcm_residual >> 1);
+
+            if (i != 0)
+                top = macroblock[idx-w];
+
+            p = left + top - topleft;
+            min_left_top = FFMIN(left, top);
+            if (p < min_left_top)
+                p = min_left_top;
+
+            max_left_top = FFMAX(left, top);
+            if (p > max_left_top)
+                p = max_left_top;
+
+            p2 = (FFMIN(min_left_top, topleft) + FFMAX(max_left_top, topleft)) >> 1;
+            if (p2 == p)
+                p2 = block_mean;
+
+            if (p2 > p)
+                dpcm_residual *= -1;
+
+            macroblock[idx++] = output = (dpcm_residual + p) & ((1 << s->avctx->bits_per_raw_sample) - 1);
+        }
+    }
+
+    return 0;
+}
+
 static int mpeg4_decode_studio_mb(MpegEncContext *s, int16_t block_[12][64])
 {
     int i;
 
+    s->dpcm_direction = 0;
+
     /* StudioMacroblock */
     /* Assumes I-VOP */
     s->mb_intra = 1;
@@ -1945,9 +2028,11 @@ static int mpeg4_decode_studio_mb(MpegEncContext *s, int16_t block_[12][64])
     } else {
         /* DPCM */
         check_marker(s->avctx, &s->gb, "DPCM block start");
-        avpriv_request_sample(s->avctx, "DPCM encoded block");
-        next_start_code_studio(&s->gb);
-        return SLICE_ERROR;
+        s->dpcm_direction = get_bits1(&s->gb) ? -1 : 1;
+        for (i = 0; i < 3; i++) {
+            if (mpeg4_decode_dpcm_macroblock(s, (*s->dpcm_macroblock)[i], i) < 0)
+                return AVERROR_INVALIDDATA;
+        }
     }
 
     if (get_bits_left(&s->gb) >= 24 && show_bits(&s->gb, 23) == 0) {
-- 
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