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libavcodec/mjpega_dump_header_bsf.c

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00001 /*
00002  * MJPEG A dump header bitstream filter
00003  * Copyright (c) 2006 Baptiste Coudurier
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00028 #include "avcodec.h"
00029 #include "bytestream.h"
00030 #include "mjpeg.h"
00031 
00032 
00033 static int mjpega_dump_header(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args,
00034                               uint8_t **poutbuf, int *poutbuf_size,
00035                               const uint8_t *buf, int buf_size, int keyframe)
00036 {
00037     uint8_t *poutbufp;
00038     unsigned dqt = 0, dht = 0, sof0 = 0;
00039     int i;
00040 
00041     if (avctx->codec_id != CODEC_ID_MJPEG) {
00042         av_log(avctx, AV_LOG_ERROR, "mjpega bitstream filter only applies to mjpeg codec\n");
00043         return 0;
00044     }
00045 
00046     *poutbuf_size = 0;
00047     *poutbuf = av_malloc(buf_size + 44 + FF_INPUT_BUFFER_PADDING_SIZE);
00048     poutbufp = *poutbuf;
00049     bytestream_put_byte(&poutbufp, 0xff);
00050     bytestream_put_byte(&poutbufp, SOI);
00051     bytestream_put_byte(&poutbufp, 0xff);
00052     bytestream_put_byte(&poutbufp, APP1);
00053     bytestream_put_be16(&poutbufp, 42); /* size */
00054     bytestream_put_be32(&poutbufp, 0);
00055     bytestream_put_buffer(&poutbufp, "mjpg", 4);
00056     bytestream_put_be32(&poutbufp, buf_size + 44); /* field size */
00057     bytestream_put_be32(&poutbufp, buf_size + 44); /* pad field size */
00058     bytestream_put_be32(&poutbufp, 0);             /* next ptr */
00059 
00060     for (i = 0; i < buf_size - 1; i++) {
00061         if (buf[i] == 0xff) {
00062             switch (buf[i + 1]) {
00063             case DQT:  dqt  = i + 46; break;
00064             case DHT:  dht  = i + 46; break;
00065             case SOF0: sof0 = i + 46; break;
00066             case SOS:
00067                 bytestream_put_be32(&poutbufp, dqt); /* quant off */
00068                 bytestream_put_be32(&poutbufp, dht); /* huff off */
00069                 bytestream_put_be32(&poutbufp, sof0); /* image off */
00070                 bytestream_put_be32(&poutbufp, i + 46); /* scan off */
00071                 bytestream_put_be32(&poutbufp, i + 46 + AV_RB16(buf + i + 2)); /* data off */
00072                 bytestream_put_buffer(&poutbufp, buf + 2, buf_size - 2); /* skip already written SOI */
00073                 *poutbuf_size = poutbufp - *poutbuf;
00074                 return 1;
00075             case APP1:
00076                 if (i + 8 < buf_size && AV_RL32(buf + i + 8) == AV_RL32("mjpg")) {
00077                     av_log(avctx, AV_LOG_ERROR, "bitstream already formatted\n");
00078                     memcpy(*poutbuf, buf, buf_size);
00079                     *poutbuf_size = buf_size;
00080                     return 1;
00081                 }
00082             }
00083         }
00084     }
00085     av_freep(poutbuf);
00086     av_log(avctx, AV_LOG_ERROR, "could not find SOS marker in bitstream\n");
00087     return 0;
00088 }
00089 
00090 AVBitStreamFilter mjpega_dump_header_bsf = {
00091     "mjpegadump",
00092     0,
00093     mjpega_dump_header,
00094 };

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