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libavcodec/mpeg4video_parser.c

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00001 /*
00002  * MPEG4 Video frame extraction
00003  * Copyright (c) 2003 Fabrice Bellard
00004  * Copyright (c) 2003 Michael Niedermayer
00005  *
00006  * This file is part of FFmpeg.
00007  *
00008  * FFmpeg 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  * FFmpeg 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 FFmpeg; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00023 #include "parser.h"
00024 #include "mpegvideo.h"
00025 #include "mpeg4video_parser.h"
00026 
00027 
00028 int ff_mpeg4_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
00029     int vop_found, i;
00030     uint32_t state;
00031 
00032     vop_found= pc->frame_start_found;
00033     state= pc->state;
00034 
00035     i=0;
00036     if(!vop_found){
00037         for(i=0; i<buf_size; i++){
00038             state= (state<<8) | buf[i];
00039             if(state == 0x1B6){
00040                 i++;
00041                 vop_found=1;
00042                 break;
00043             }
00044         }
00045     }
00046 
00047     if(vop_found){
00048         /* EOF considered as end of frame */
00049         if (buf_size == 0)
00050             return 0;
00051         for(; i<buf_size; i++){
00052             state= (state<<8) | buf[i];
00053             if((state&0xFFFFFF00) == 0x100){
00054                 pc->frame_start_found=0;
00055                 pc->state=-1;
00056                 return i-3;
00057             }
00058         }
00059     }
00060     pc->frame_start_found= vop_found;
00061     pc->state= state;
00062     return END_NOT_FOUND;
00063 }
00064 
00065 /* XXX: make it use less memory */
00066 static int av_mpeg4_decode_header(AVCodecParserContext *s1,
00067                                   AVCodecContext *avctx,
00068                                   const uint8_t *buf, int buf_size)
00069 {
00070     ParseContext1 *pc = s1->priv_data;
00071     MpegEncContext *s = pc->enc;
00072     GetBitContext gb1, *gb = &gb1;
00073     int ret;
00074 
00075     s->avctx = avctx;
00076     s->current_picture_ptr = &s->current_picture;
00077 
00078     if (avctx->extradata_size && pc->first_picture){
00079         init_get_bits(gb, avctx->extradata, avctx->extradata_size*8);
00080         ret = ff_mpeg4_decode_picture_header(s, gb);
00081     }
00082 
00083     init_get_bits(gb, buf, 8 * buf_size);
00084     ret = ff_mpeg4_decode_picture_header(s, gb);
00085     if (s->width) {
00086         avcodec_set_dimensions(avctx, s->width, s->height);
00087     }
00088     s1->pict_type= s->pict_type;
00089     pc->first_picture = 0;
00090     return ret;
00091 }
00092 
00093 static av_cold int mpeg4video_parse_init(AVCodecParserContext *s)
00094 {
00095     ParseContext1 *pc = s->priv_data;
00096 
00097     pc->enc = av_mallocz(sizeof(MpegEncContext));
00098     if (!pc->enc)
00099         return -1;
00100     pc->first_picture = 1;
00101     return 0;
00102 }
00103 
00104 static int mpeg4video_parse(AVCodecParserContext *s,
00105                            AVCodecContext *avctx,
00106                            const uint8_t **poutbuf, int *poutbuf_size,
00107                            const uint8_t *buf, int buf_size)
00108 {
00109     ParseContext *pc = s->priv_data;
00110     int next;
00111 
00112     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
00113         next= buf_size;
00114     }else{
00115         next= ff_mpeg4_find_frame_end(pc, buf, buf_size);
00116 
00117         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
00118             *poutbuf = NULL;
00119             *poutbuf_size = 0;
00120             return buf_size;
00121         }
00122     }
00123     av_mpeg4_decode_header(s, avctx, buf, buf_size);
00124 
00125     *poutbuf = buf;
00126     *poutbuf_size = buf_size;
00127     return next;
00128 }
00129 
00130 
00131 AVCodecParser mpeg4video_parser = {
00132     { CODEC_ID_MPEG4 },
00133     sizeof(ParseContext1),
00134     mpeg4video_parse_init,
00135     mpeg4video_parse,
00136     ff_parse1_close,
00137     ff_mpeg4video_split,
00138 };

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