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libavcodec/mpegvideo_parser.c

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00001 /*
00002  * MPEG1 / MPEG2 video parser
00003  * Copyright (c) 2000,2001 Fabrice Bellard
00004  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
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 
00026 static void mpegvideo_extract_headers(AVCodecParserContext *s,
00027                                       AVCodecContext *avctx,
00028                                       const uint8_t *buf, int buf_size)
00029 {
00030     ParseContext1 *pc = s->priv_data;
00031     const uint8_t *buf_end = buf + buf_size;
00032     uint32_t start_code;
00033     int frame_rate_index, ext_type, bytes_left;
00034     int frame_rate_ext_n, frame_rate_ext_d;
00035     int picture_structure, top_field_first, repeat_first_field, progressive_frame;
00036     int horiz_size_ext, vert_size_ext, bit_rate_ext;
00037     int did_set_size=0;
00038 //FIXME replace the crap with get_bits()
00039     s->repeat_pict = 0;
00040 
00041     while (buf < buf_end) {
00042         start_code= -1;
00043         buf= ff_find_start_code(buf, buf_end, &start_code);
00044         bytes_left = buf_end - buf;
00045         switch(start_code) {
00046         case PICTURE_START_CODE:
00047             if (bytes_left >= 2) {
00048                 s->pict_type = (buf[1] >> 3) & 7;
00049             }
00050             break;
00051         case SEQ_START_CODE:
00052             if (bytes_left >= 7) {
00053                 pc->width  = (buf[0] << 4) | (buf[1] >> 4);
00054                 pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
00055                 if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
00056                     avcodec_set_dimensions(avctx, pc->width, pc->height);
00057                     did_set_size=1;
00058                 }
00059                 frame_rate_index = buf[3] & 0xf;
00060                 pc->frame_rate.den = avctx->time_base.den = ff_frame_rate_tab[frame_rate_index].num;
00061                 pc->frame_rate.num = avctx->time_base.num = ff_frame_rate_tab[frame_rate_index].den;
00062                 avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
00063                 avctx->codec_id = CODEC_ID_MPEG1VIDEO;
00064                 avctx->sub_id = 1;
00065             }
00066             break;
00067         case EXT_START_CODE:
00068             if (bytes_left >= 1) {
00069                 ext_type = (buf[0] >> 4);
00070                 switch(ext_type) {
00071                 case 0x1: /* sequence extension */
00072                     if (bytes_left >= 6) {
00073                         horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
00074                         vert_size_ext = (buf[2] >> 5) & 3;
00075                         bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
00076                         frame_rate_ext_n = (buf[5] >> 5) & 3;
00077                         frame_rate_ext_d = (buf[5] & 0x1f);
00078                         pc->progressive_sequence = buf[1] & (1 << 3);
00079                         avctx->has_b_frames= !(buf[5] >> 7);
00080 
00081                         pc->width  |=(horiz_size_ext << 12);
00082                         pc->height |=( vert_size_ext << 12);
00083                         avctx->bit_rate += (bit_rate_ext << 18) * 400;
00084                         if(did_set_size)
00085                             avcodec_set_dimensions(avctx, pc->width, pc->height);
00086                         avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
00087                         avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
00088                         avctx->codec_id = CODEC_ID_MPEG2VIDEO;
00089                         avctx->sub_id = 2; /* forces MPEG2 */
00090                     }
00091                     break;
00092                 case 0x8: /* picture coding extension */
00093                     if (bytes_left >= 5) {
00094                         picture_structure = buf[2]&3;
00095                         top_field_first = buf[3] & (1 << 7);
00096                         repeat_first_field = buf[3] & (1 << 1);
00097                         progressive_frame = buf[4] & (1 << 7);
00098 
00099                         /* check if we must repeat the frame */
00100                         s->repeat_pict = 1;
00101                         if (repeat_first_field) {
00102                             if (pc->progressive_sequence) {
00103                                 if (top_field_first)
00104                                     s->repeat_pict = 5;
00105                                 else
00106                                     s->repeat_pict = 3;
00107                             } else if (progressive_frame) {
00108                                 s->repeat_pict = 2;
00109                             }
00110                         }
00111                     }
00112                     break;
00113                 }
00114             }
00115             break;
00116         case -1:
00117             goto the_end;
00118         default:
00119             /* we stop parsing when we encounter a slice. It ensures
00120                that this function takes a negligible amount of time */
00121             if (start_code >= SLICE_MIN_START_CODE &&
00122                 start_code <= SLICE_MAX_START_CODE)
00123                 goto the_end;
00124             break;
00125         }
00126     }
00127  the_end: ;
00128 }
00129 
00130 static int mpegvideo_parse(AVCodecParserContext *s,
00131                            AVCodecContext *avctx,
00132                            const uint8_t **poutbuf, int *poutbuf_size,
00133                            const uint8_t *buf, int buf_size)
00134 {
00135     ParseContext1 *pc1 = s->priv_data;
00136     ParseContext *pc= &pc1->pc;
00137     int next;
00138 
00139     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
00140         next= buf_size;
00141     }else{
00142         next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
00143 
00144         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
00145             *poutbuf = NULL;
00146             *poutbuf_size = 0;
00147             return buf_size;
00148         }
00149 
00150     }
00151     /* we have a full frame : we just parse the first few MPEG headers
00152        to have the full timing information. The time take by this
00153        function should be negligible for uncorrupted streams */
00154     mpegvideo_extract_headers(s, avctx, buf, buf_size);
00155 #if 0
00156     printf("pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
00157            s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
00158 #endif
00159 
00160     *poutbuf = buf;
00161     *poutbuf_size = buf_size;
00162     return next;
00163 }
00164 
00165 static int mpegvideo_split(AVCodecContext *avctx,
00166                            const uint8_t *buf, int buf_size)
00167 {
00168     int i;
00169     uint32_t state= -1;
00170 
00171     for(i=0; i<buf_size; i++){
00172         state= (state<<8) | buf[i];
00173         if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
00174             return i-3;
00175     }
00176     return 0;
00177 }
00178 
00179 AVCodecParser mpegvideo_parser = {
00180     { CODEC_ID_MPEG1VIDEO, CODEC_ID_MPEG2VIDEO },
00181     sizeof(ParseContext1),
00182     NULL,
00183     mpegvideo_parse,
00184     ff_parse1_close,
00185     mpegvideo_split,
00186 };

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