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libavformat/mpegvideodec.c

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00001 /*
00002  * RAW MPEG video demuxer
00003  * Copyright (c) 2002-2003 Fabrice Bellard
00004  * Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
00005  *
00006  * This file is part of Libav.
00007  *
00008  * Libav is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * Libav is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with Libav; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00023 #include "avformat.h"
00024 #include "rawdec.h"
00025 
00026 #define SEQ_START_CODE          0x000001b3
00027 #define GOP_START_CODE          0x000001b8
00028 #define PICTURE_START_CODE      0x00000100
00029 #define SLICE_START_CODE        0x00000101
00030 #define PACK_START_CODE         0x000001ba
00031 #define VIDEO_ID                0x000001e0
00032 #define AUDIO_ID                0x000001c0
00033 
00034 static int mpegvideo_probe(AVProbeData *p)
00035 {
00036     uint32_t code= -1;
00037     int pic=0, seq=0, slice=0, pspack=0, pes=0;
00038     int i;
00039 
00040     for(i=0; i<p->buf_size; i++){
00041         code = (code<<8) + p->buf[i];
00042         if ((code & 0xffffff00) == 0x100) {
00043             switch(code){
00044             case     SEQ_START_CODE:   seq++; break;
00045             case PICTURE_START_CODE:   pic++; break;
00046             case   SLICE_START_CODE: slice++; break;
00047             case    PACK_START_CODE: pspack++; break;
00048             }
00049             if     ((code & 0x1f0) == VIDEO_ID)   pes++;
00050             else if((code & 0x1e0) == AUDIO_ID)   pes++;
00051         }
00052     }
00053     if(seq && seq*9<=pic*10 && pic*9<=slice*10 && !pspack && !pes)
00054         return pic>1 ? AVPROBE_SCORE_MAX/2+1 : AVPROBE_SCORE_MAX/4; // +1 for .mpg
00055     return 0;
00056 }
00057 
00058 FF_DEF_RAWVIDEO_DEMUXER(mpegvideo, "raw MPEG video", mpegvideo_probe, NULL, CODEC_ID_MPEG1VIDEO)
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