libavcodec/mpegvideo_parser.c

   1 /*
   2  * MPEG1 / MPEG2 video parser
   3  * Copyright (c) 2000,2001 Fabrice Bellard.
   4  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "parser.h"
  24 #include "mpegvideo.h"
  25
  26 static void mpegvideo_extract_headers(AVCodecParserContext *s,
  27                                       AVCodecContext *avctx,
  28                                       const uint8_t *buf, int buf_size)
  29 {
  30     ParseContext1 *pc = s->priv_data;
  31     const uint8_t *buf_end;
  32     uint32_t start_code;
  33     int frame_rate_index, ext_type, bytes_left;
  34     int frame_rate_ext_n, frame_rate_ext_d;
  35     int picture_structure, top_field_first, repeat_first_field, progressive_frame;
  36     int horiz_size_ext, vert_size_ext, bit_rate_ext;
  37 //FIXME replace the crap with get_bits()
  38     s->repeat_pict = 0;
  39     buf_end = buf + buf_size;
  40     while (buf < buf_end) {
  41         start_code= -1;
  42         buf= ff_find_start_code(buf, buf_end, &start_code);
  43         bytes_left = buf_end - buf;
  44         switch(start_code) {
  45         case PICTURE_START_CODE:
  46             if (bytes_left >= 2) {
  47                 s->pict_type = (buf[1] >> 3) & 7;
  48             }
  49             break;
  50         case SEQ_START_CODE:
  51             if (bytes_left >= 7) {
  52                 pc->width  = (buf[0] << 4) | (buf[1] >> 4);
  53                 pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
  54                 avcodec_set_dimensions(avctx, pc->width, pc->height);
  55                 frame_rate_index = buf[3] & 0xf;
  56                 pc->frame_rate.den = avctx->time_base.den = ff_frame_rate_tab[frame_rate_index].num;
  57                 pc->frame_rate.num = avctx->time_base.num = ff_frame_rate_tab[frame_rate_index].den;
  58                 avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
  59                 avctx->codec_id = CODEC_ID_MPEG1VIDEO;
  60                 avctx->sub_id = 1;
  61             }
  62             break;
  63         case EXT_START_CODE:
  64             if (bytes_left >= 1) {
  65                 ext_type = (buf[0] >> 4);
  66                 switch(ext_type) {
  67                 case 0x1: /* sequence extension */
  68                     if (bytes_left >= 6) {
  69                         horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
  70                         vert_size_ext = (buf[2] >> 5) & 3;
  71                         bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
  72                         frame_rate_ext_n = (buf[5] >> 5) & 3;
  73                         frame_rate_ext_d = (buf[5] & 0x1f);
  74                         pc->progressive_sequence = buf[1] & (1 << 3);
  75                         avctx->has_b_frames= !(buf[5] >> 7);
  76
  77                         pc->width  |=(horiz_size_ext << 12);
  78                         pc->height |=( vert_size_ext << 12);
  79                         avctx->bit_rate += (bit_rate_ext << 18) * 400;
  80                         avcodec_set_dimensions(avctx, pc->width, pc->height);
  81                         avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1);
  82                         avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
  83                         avctx->codec_id = CODEC_ID_MPEG2VIDEO;
  84                         avctx->sub_id = 2; /* forces MPEG2 */
  85                     }
  86                     break;
  87                 case 0x8: /* picture coding extension */
  88                     if (bytes_left >= 5) {
  89                         picture_structure = buf[2]&3;
  90                         top_field_first = buf[3] & (1 << 7);
  91                         repeat_first_field = buf[3] & (1 << 1);
  92                         progressive_frame = buf[4] & (1 << 7);
  93
  94                         /* check if we must repeat the frame */
  95                         if (repeat_first_field) {
  96                             if (pc->progressive_sequence) {
  97                                 if (top_field_first)
  98                                     s->repeat_pict = 4;
  99                                 else
 100                                     s->repeat_pict = 2;
 101                             } else if (progressive_frame) {
 102                                 s->repeat_pict = 1;
 103                             }
 104                         }
 105                     }
 106                     break;
 107                 }
 108             }
 109             break;
 110         case -1:
 111             goto the_end;
 112         default:
 113             /* we stop parsing when we encounter a slice. It ensures
 114                that this function takes a negligible amount of time */
 115             if (start_code >= SLICE_MIN_START_CODE &&
 116                 start_code <= SLICE_MAX_START_CODE)
 117                 goto the_end;
 118             break;
 119         }
 120     }
 121  the_end: ;
 122 }
 123
 124 static int mpegvideo_parse(AVCodecParserContext *s,
 125                            AVCodecContext *avctx,
 126                            const uint8_t **poutbuf, int *poutbuf_size,
 127                            const uint8_t *buf, int buf_size)
 128 {
 129     ParseContext1 *pc1 = s->priv_data;
 130     ParseContext *pc= &pc1->pc;
 131     int next;
 132
 133     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
 134         next= buf_size;
 135     }else{
 136         next= ff_mpeg1_find_frame_end(pc, buf, buf_size);
 137
 138         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 139             *poutbuf = NULL;
 140             *poutbuf_size = 0;
 141             return buf_size;
 142         }
 143
 144     }
 145     /* we have a full frame : we just parse the first few MPEG headers
 146        to have the full timing information. The time take by this
 147        function should be negligible for uncorrupted streams */
 148     mpegvideo_extract_headers(s, avctx, buf, buf_size);
 149 #if 0
 150     printf("pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
 151            s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
 152 #endif
 153
 154     *poutbuf = buf;
 155     *poutbuf_size = buf_size;
 156     return next;
 157 }
 158
 159 static int mpegvideo_split(AVCodecContext *avctx,
 160                            const uint8_t *buf, int buf_size)
 161 {
 162     int i;
 163     uint32_t state= -1;
 164
 165     for(i=0; i<buf_size; i++){
 166         state= (state<<8) | buf[i];
 167         if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
 168             return i-3;
 169     }
 170     return 0;
 171 }
 172
 173 AVCodecParser mpegvideo_parser = {
 174     { CODEC_ID_MPEG1VIDEO, CODEC_ID_MPEG2VIDEO },
 175     sizeof(ParseContext1),
 176     NULL,
 177     mpegvideo_parse,
 178     ff_parse1_close,
 179 };