QT RLE encoder

patch by Alexis Ballier: [alexis ballier gmail com]
original thread: [FFmpeg-devel] [Patch] QT RLE encoder, bis
date: 06/24/2007 03:56 PM

Originally committed as revision 9452 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 327 insertions, 0 deletions

diff --git a/libavcodec/qtrleenc.c b/libavcodec/qtrleenc.c
new file mode 100644
index 0000000000..eaa1b3dbbe
--- /dev/null
+++ b/libavcodec/qtrleenc.c
@@ -0,0 +1,327 @@
+/*
+ * Quicktime Animation (RLE) Video Encoder
+ * Copyright (C) 2007 Clemens Fruhwirth
+ * Copyright (C) 2007 Alexis Ballier
+ *
+ * This file is part of FFmpeg.
+ *
+ * This file is based on flashsvenc.c
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License, version 2.1, as published by the Free Software Foundation
+ *
+ * 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser 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
+ *
+ */
+
+#include "avcodec.h"
+#include "bytestream.h"
+
+/** Maximum RLE code for bulk copy */
+#define MAX_RLE_BULK   127
+/** Maximum RLE code for repeat */
+#define MAX_RLE_REPEAT 128
+/** Maximum RLE code for skip */
+#define MAX_RLE_SKIP   254
+
+typedef struct QtrleEncContext {
+    AVCodecContext *avctx;
+    AVFrame frame;
+    int pixel_size;
+    AVPicture previous_frame;
+    unsigned int max_buf_size;
+    /**
+     * This array will contain at ith position the value of the best RLE code
+     * if the line started at pixel i
+     * There can be 3 values :
+     * skip (0)     : skip as much as possible pixels because they are equal to the
+     *                previous frame ones
+     * repeat (<-1) : repeat that pixel -rle_code times, still as much as
+     *                possible
+     * copy (>0)    : copy the raw next rle_code pixels */
+    signed char *rlecode_table;
+    /**
+     * This array will contain the length of the best rle encoding of the line
+     * starting at ith pixel */
+    int *length_table;
+    /**
+     * Will contain at ith position the number of consecutive pixels equal to the previous
+     * frame starting from pixel i */
+    uint8_t* skip_table;
+} QtrleEncContext;
+
+static int qtrle_encode_init(AVCodecContext *avctx)
+{
+    QtrleEncContext *s = avctx->priv_data;
+
+    if (avcodec_check_dimensions(avctx, avctx->width, avctx->height) < 0) {
+        return -1;
+    }
+    s->avctx=avctx;
+
+    switch (avctx->pix_fmt) {
+/*    case PIX_FMT_RGB555:
+        s->pixel_size = 2;
+        break;*/
+    case PIX_FMT_RGB24:
+        s->pixel_size = 3;
+        break;
+    default:
+        av_log(avctx, AV_LOG_ERROR, "Unsupported colorspace.\n");
+        break;
+    }
+    avctx->bits_per_sample = s->pixel_size*8;
+
+    s->rlecode_table = av_mallocz(s->avctx->width);
+    s->skip_table    = av_mallocz(s->avctx->width);
+    s->length_table  = av_mallocz((s->avctx->width + 1)*sizeof(int));
+    if (!s->skip_table || !s->length_table || !s->rlecode_table) {
+        av_log(avctx, AV_LOG_ERROR, "Error allocating memory.\n");
+        return -1;
+    }
+    if (avpicture_alloc(&s->previous_frame, avctx->pix_fmt, avctx->width, avctx->height) < 0) {
+        av_log(avctx, AV_LOG_ERROR, "Error allocating picture\n");
+        return -1;
+    }
+
+    s->max_buf_size = s->avctx->width*s->avctx->height*s->pixel_size /* image base material */
+                      + 15                                           /* header + footer */
+                      + s->avctx->height*2                           /* skip code+rle end */
+                      + s->avctx->width/MAX_RLE_BULK + 1             /* rle codes */;
+    avctx->coded_frame = &s->frame;
+    return 0;
+}
+
+/**
+ * Computes the best RLE sequence for a line
+ */
+static void qtrle_encode_line(QtrleEncContext *s, AVFrame *p, int line, uint8_t **buf)
+{
+    int width=s->avctx->width;
+    int i;
+    signed char rlecode;
+
+    /* We will use it to compute the best bulk copy sequence */
+    unsigned int bulkcount;
+    /* This will be the number of pixels equal to the preivous frame one's
+     * starting from the ith pixel */
+    unsigned int skipcount;
+    /* This will be the number of consecutive equal pixels in the current
+     * frame, starting from the ith one also */
+    unsigned int repeatcount;
+
+    /* The cost of the three different possibilities */
+    int total_bulk_cost;
+    int total_skip_cost;
+    int total_repeat_cost;
+
+    int temp_cost;
+    int j;
+
+    uint8_t *this_line = p->               data[0] + line*p->linesize[0] + (width - 1)*s->pixel_size;
+    uint8_t *prev_line = s->previous_frame.data[0] + line*p->linesize[0] + (width - 1)*s->pixel_size;
+
+    s->length_table[width] = 0;
+    skipcount = 0;
+
+    for (i = width - 1; i >= 0; i--) {
+
+        if (!s->frame.key_frame && !memcmp(this_line, prev_line, s->pixel_size))
+            skipcount = FFMIN(skipcount + 1, MAX_RLE_SKIP);
+        else
+            skipcount = 0;
+
+        total_skip_cost  = s->length_table[i + skipcount] + 2;
+        s->skip_table[i] = skipcount;
+
+
+        if (i < width - 1 && !memcmp(this_line, this_line + s->pixel_size, s->pixel_size))
+            repeatcount = FFMIN(repeatcount + 1, MAX_RLE_REPEAT);
+        else
+            repeatcount = 1;
+
+        total_repeat_cost = s->length_table[i + repeatcount] + 1 + s->pixel_size;
+
+        /* skip code is free for the first pixel, it costs one byte for repeat and bulk copy
+         * so let's make it aware */
+        if (i == 0) {
+            total_skip_cost--;
+            total_repeat_cost++;
+        }
+
+        if (repeatcount > 1 && (skipcount == 0 || total_repeat_cost < total_skip_cost)) {
+            /* repeat is the best */
+            s->length_table[i]  = total_repeat_cost;
+            s->rlecode_table[i] = -repeatcount;
+        }
+        else if (skipcount > 0) {
+            /* skip is the best choice here */
+            s->length_table[i]  = total_skip_cost;
+            s->rlecode_table[i] = 0;
+        }
+        else {
+            /* We cannot do neither skip nor repeat
+             * thus we search for the best bulk copy to do */
+
+            int limit = FFMIN(width - i, MAX_RLE_BULK);
+
+            temp_cost = 1 + s->pixel_size + !i;
+            total_bulk_cost = INT_MAX;
+
+            for (j = 1; j <= limit; j++) {
+                if (s->length_table[i + j] + temp_cost < total_bulk_cost) {
+                    /* We have found a better bulk copy ... */
+                    total_bulk_cost = s->length_table[i + j] + temp_cost;
+                    bulkcount = j;
+                }
+                temp_cost += s->pixel_size;
+            }
+
+            s->length_table[i]  = total_bulk_cost;
+            s->rlecode_table[i] = bulkcount;
+        }
+
+        this_line -= s->pixel_size;
+        prev_line -= s->pixel_size;
+    }
+
+    /* Good ! Now we have the best sequence for this line, let's ouput it */
+
+    /* We do a special case for the first pixel so that we avoid testing it in
+     * the whole loop */
+
+    i=0;
+    this_line = p->               data[0] + line*p->linesize[0];
+    prev_line = s->previous_frame.data[0] + line*p->linesize[0];
+
+    if (s->rlecode_table[0] == 0) {
+        bytestream_put_byte(buf, s->skip_table[0] + 1);
+        i += s->skip_table[0];
+    }
+    else bytestream_put_byte(buf, 1);
+
+
+    while (i < width) {
+        rlecode = s->rlecode_table[i];
+        bytestream_put_byte(buf, rlecode);
+        if (rlecode == 0) {
+            /* Write a skip sequence */
+            bytestream_put_byte(buf, s->skip_table[i] + 1);
+            i += s->skip_table[i];
+        }
+        else if (rlecode > 0) {
+            /* bulk copy */
+            bytestream_put_buffer(buf, this_line + i*s->pixel_size, rlecode*s->pixel_size);
+            i += rlecode;
+        }
+        else {
+            /* repeat the bits */
+            bytestream_put_buffer(buf, this_line + i*s->pixel_size, s->pixel_size);
+            i -= rlecode;
+        }
+    }
+    bytestream_put_byte(buf, -1); // end RLE line
+}
+
+/** Encodes frame including header */
+static int encode_frame(QtrleEncContext *s, AVFrame *p, uint8_t *buf)
+{
+    int i;
+    int start_line = 0;
+    int end_line = s->avctx->height;
+    uint8_t *orig_buf = buf;
+
+    if (!s->frame.key_frame) {
+        for (start_line = 0; start_line < s->avctx->height; start_line++)
+            if (memcmp(p->data[0] + start_line*p->linesize[0],
+                       s->previous_frame.data[0] + start_line*p->linesize[0],
+                       p->linesize[0]))
+                break;
+
+        for (end_line=s->avctx->height; end_line > start_line; end_line--)
+            if (memcmp(p->data[0] + (end_line - 1)*p->linesize[0],
+                       s->previous_frame.data[0] + (end_line - 1)*p->linesize[0],
+                       p->linesize[0]))
+                break;
+    }
+
+    bytestream_put_be32(&buf, 0);                         // CHUNK SIZE, patched later
+
+    if (start_line == 0 && end_line == s->avctx->height || start_line == s->avctx->height)
+        bytestream_put_be16(&buf, 0);                     // header
+    else {
+        bytestream_put_be16(&buf, 8);                     // header
+        bytestream_put_be16(&buf, start_line);            // starting line
+        bytestream_put_be16(&buf, 0);                     // unknown
+        bytestream_put_be16(&buf, end_line - start_line); // lines to update
+        bytestream_put_be16(&buf, 0);                     // unknown
+    }
+    for (i = start_line; i < end_line; i++)
+        qtrle_encode_line(s, p, i, &buf);
+
+    bytestream_put_byte(&buf, 0);                         // zero skip code = frame finished
+    AV_WB32(orig_buf, buf - orig_buf);                    // patch the chunk size
+    return buf - orig_buf;
+}
+
+static int qtrle_encode_frame(AVCodecContext *avctx, uint8_t *buf, int buf_size, void *data)
+{
+    QtrleEncContext * const s = avctx->priv_data;
+    AVFrame *pict = data;
+    AVFrame * const p = &s->frame;
+    int chunksize;
+
+    *p = *pict;
+
+    if (buf_size < s->max_buf_size) {
+        /* Upper bound check for compressed data */
+        av_log(avctx, AV_LOG_ERROR, "buf_size %d <  %d\n", buf_size, s->max_buf_size);
+        return -1;
+    }
+
+    if (avctx->gop_size == 0 || (s->avctx->frame_number % avctx->gop_size) == 0) {
+        /* I-Frame */
+        p->pict_type = FF_I_TYPE;
+        p->key_frame = 1;
+    } else {
+        /* P-Frame */
+        p->pict_type = FF_P_TYPE;
+        p->key_frame = 0;
+    }
+
+    chunksize = encode_frame(s, pict, buf);
+
+    /* save the current frame */
+    av_picture_copy(&s->previous_frame, (AVPicture *)p, avctx->pix_fmt, avctx->width, avctx->height);
+    return chunksize;
+}
+
+static int qtrle_encode_end(AVCodecContext *avctx)
+{
+    QtrleEncContext *s = avctx->priv_data;
+
+    avpicture_free(&s->previous_frame);
+    av_free(s->rlecode_table);
+    av_free(s->length_table);
+    av_free(s->skip_table);
+    return 0;
+}
+
+AVCodec qtrle_encoder = {
+    "qtrle",
+    CODEC_TYPE_VIDEO,
+    CODEC_ID_QTRLE,
+    sizeof(QtrleEncContext),
+    qtrle_encode_init,
+    qtrle_encode_frame,
+    qtrle_encode_end,
+    .pix_fmts = (enum PixelFormat[]){PIX_FMT_RGB24, -1},
+};