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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.h"
00026 #include "mpeg4video_parser.h"
00027 
00028 
00029 int ff_mpeg4_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
00030     int vop_found, i;
00031     uint32_t state;
00032 
00033     vop_found= pc->frame_start_found;
00034     state= pc->state;
00035 
00036     i=0;
00037     if(!vop_found){
00038         for(i=0; i<buf_size; i++){
00039             state= (state<<8) | buf[i];
00040             if(state == 0x1B6){
00041                 i++;
00042                 vop_found=1;
00043                 break;
00044             }
00045         }
00046     }
00047 
00048     if(vop_found){
00049         /* EOF considered as end of frame */
00050         if (buf_size == 0)
00051             return 0;
00052         for(; i<buf_size; i++){
00053             state= (state<<8) | buf[i];
00054             if((state&0xFFFFFF00) == 0x100){
00055                 pc->frame_start_found=0;
00056                 pc->state=-1;
00057                 return i-3;
00058             }
00059         }
00060     }
00061     pc->frame_start_found= vop_found;
00062     pc->state= state;
00063     return END_NOT_FOUND;
00064 }
00065 
00066 /* XXX: make it use less memory */
00067 static int av_mpeg4_decode_header(AVCodecParserContext *s1,
00068                                   AVCodecContext *avctx,
00069                                   const uint8_t *buf, int buf_size)
00070 {
00071     ParseContext1 *pc = s1->priv_data;
00072     MpegEncContext *s = pc->enc;
00073     GetBitContext gb1, *gb = &gb1;
00074     int ret;
00075 
00076     s->avctx = avctx;
00077     s->current_picture_ptr = &s->current_picture;
00078 
00079     if (avctx->extradata_size && pc->first_picture){
00080         init_get_bits(gb, avctx->extradata, avctx->extradata_size*8);
00081         ret = ff_mpeg4_decode_picture_header(s, gb);
00082     }
00083 
00084     init_get_bits(gb, buf, 8 * buf_size);
00085     ret = ff_mpeg4_decode_picture_header(s, gb);
00086     if (s->width && (!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height)) {
00087         avcodec_set_dimensions(avctx, s->width, s->height);
00088     }
00089     s1->pict_type= s->pict_type;
00090     pc->first_picture = 0;
00091     return ret;
00092 }
00093 
00094 static av_cold int mpeg4video_parse_init(AVCodecParserContext *s)
00095 {
00096     ParseContext1 *pc = s->priv_data;
00097 
00098     pc->enc = av_mallocz(sizeof(MpegEncContext));
00099     if (!pc->enc)
00100         return -1;
00101     pc->first_picture = 1;
00102     return 0;
00103 }
00104 
00105 static int mpeg4video_parse(AVCodecParserContext *s,
00106                            AVCodecContext *avctx,
00107                            const uint8_t **poutbuf, int *poutbuf_size,
00108                            const uint8_t *buf, int buf_size)
00109 {
00110     ParseContext *pc = s->priv_data;
00111     int next;
00112 
00113     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
00114         next= buf_size;
00115     }else{
00116         next= ff_mpeg4_find_frame_end(pc, buf, buf_size);
00117 
00118         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
00119             *poutbuf = NULL;
00120             *poutbuf_size = 0;
00121             return buf_size;
00122         }
00123     }
00124     av_mpeg4_decode_header(s, avctx, buf, buf_size);
00125 
00126     *poutbuf = buf;
00127     *poutbuf_size = buf_size;
00128     return next;
00129 }
00130 
00131 
00132 AVCodecParser mpeg4video_parser = {
00133     { CODEC_ID_MPEG4 },
00134     sizeof(ParseContext1),
00135     mpeg4video_parse_init,
00136     mpeg4video_parse,
00137     ff_parse1_close,
00138     ff_mpeg4video_split,
00139 };

Generated on Fri Sep 16 2011 17:17:40 for FFmpeg by  doxygen 1.7.1