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     const uint8_t *buf_start= buf;
  33     uint32_t start_code;
  34     int frame_rate_index, ext_type, bytes_left;
  35     int frame_rate_ext_n, frame_rate_ext_d;
  36     int picture_structure, top_field_first, repeat_first_field, progressive_frame;
  37     int horiz_size_ext, vert_size_ext, bit_rate_ext;
  38 //FIXME replace the crap with get_bits()
  39     s->repeat_pict = 0;
  40     buf_end = buf + buf_size;
  41     while (buf < buf_end) {
  42         start_code= -1;
  43         buf= ff_find_start_code(buf, buf_end, &start_code);
  44         bytes_left = buf_end - buf;
  45         switch(start_code) {
  46         case PICTURE_START_CODE:
  47             ff_fetch_timestamp(s, buf-buf_start-4, 1);
  48
  49             if (bytes_left >= 2) {
  50                 s->pict_type = (buf[1] >> 3) & 7;
  51             }
  52             break;
  53         case SEQ_START_CODE:
  54             if (bytes_left >= 7) {
  55                 pc->width  = (buf[0] << 4) | (buf[1] >> 4);
  56                 pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
  57                 avcodec_set_dimensions(avctx, pc->width, pc->height);
  58                 frame_rate_index = buf[3] & 0xf;
  59                 pc->frame_rate.den = avctx->time_base.den = ff_frame_rate_tab[frame_rate_index].num;
  60                 pc->frame_rate.num = avctx->time_base.num = ff_frame_rate_tab[frame_rate_index].den;
  61                 avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
  62                 avctx->codec_id = CODEC_ID_MPEG1VIDEO;
  63                 avctx->sub_id = 1;
  64             }
  65             break;
  66         case EXT_START_CODE:
  67             if (bytes_left >= 1) {
  68                 ext_type = (buf[0] >> 4);
  69                 switch(ext_type) {
  70                 case 0x1: /* sequence extension */
  71                     if (bytes_left >= 6) {
  72                         horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
  73                         vert_size_ext = (buf[2] >> 5) & 3;
  74                         bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
  75                         frame_rate_ext_n = (buf[5] >> 5) & 3;
  76                         frame_rate_ext_d = (buf[5] & 0x1f);
  77                         pc->progressive_sequence = buf[1] & (1 << 3);
  78                         avctx->has_b_frames= !(buf[5] >> 7);
  79
  80                         pc->width  |=(horiz_size_ext << 12);
  81                         pc->height |=( vert_size_ext << 12);
  82                         avctx->bit_rate += (bit_rate_ext << 18) * 400;
  83                         avcodec_set_dimensions(avctx, pc->width, pc->height);
  84                         avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1);
  85                         avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
  86                         avctx->codec_id = CODEC_ID_MPEG2VIDEO;
  87                         avctx->sub_id = 2; /* forces MPEG2 */
  88                     }
  89                     break;
  90                 case 0x8: /* picture coding extension */
  91                     if (bytes_left >= 5) {
  92                         picture_structure = buf[2]&3;
  93                         top_field_first = buf[3] & (1 << 7);
  94                         repeat_first_field = buf[3] & (1 << 1);
  95                         progressive_frame = buf[4] & (1 << 7);
  96
  97                         /* check if we must repeat the frame */
  98                         if (repeat_first_field) {
  99                             if (pc->progressive_sequence) {
 100                                 if (top_field_first)
 101                                     s->repeat_pict = 4;
 102                                 else
 103                                     s->repeat_pict = 2;
 104                             } else if (progressive_frame) {
 105                                 s->repeat_pict = 1;
 106                             }
 107                         }
 108                     }
 109                     break;
 110                 }
 111             }
 112             break;
 113         case -1:
 114             goto the_end;
 115         default:
 116             /* we stop parsing when we encounter a slice. It ensures
 117                that this function takes a negligible amount of time */
 118             if (start_code >= SLICE_MIN_START_CODE &&
 119                 start_code <= SLICE_MAX_START_CODE)
 120                 goto the_end;
 121             break;
 122         }
 123     }
 124  the_end: ;
 125 }
 126
 127 static int mpegvideo_parse(AVCodecParserContext *s,
 128                            AVCodecContext *avctx,
 129                            const uint8_t **poutbuf, int *poutbuf_size,
 130                            const uint8_t *buf, int buf_size)
 131 {
 132     ParseContext1 *pc1 = s->priv_data;
 133     ParseContext *pc= &pc1->pc;
 134     int next;
 135
 136     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
 137         next= buf_size;
 138     }else{
 139         next= ff_mpeg1_find_frame_end(pc, buf, buf_size);
 140
 141         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 142             *poutbuf = NULL;
 143             *poutbuf_size = 0;
 144             return buf_size;
 145         }
 146
 147     }
 148     /* we have a full frame : we just parse the first few MPEG headers
 149        to have the full timing information. The time take by this
 150        function should be negligible for uncorrupted streams */
 151     mpegvideo_extract_headers(s, avctx, buf, buf_size);
 152 #if 0
 153     printf("pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
 154            s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
 155 #endif
 156
 157     *poutbuf = buf;
 158     *poutbuf_size = buf_size;
 159     return next;
 160 }
 161
 162 static int mpegvideo_split(AVCodecContext *avctx,
 163                            const uint8_t *buf, int buf_size)
 164 {
 165     int i;
 166     uint32_t state= -1;
 167
 168     for(i=0; i<buf_size; i++){
 169         state= (state<<8) | buf[i];
 170         if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
 171             return i-3;
 172     }
 173     return 0;
 174 }
 175
 176 AVCodecParser mpegvideo_parser = {
 177     { CODEC_ID_MPEG1VIDEO, CODEC_ID_MPEG2VIDEO },
 178     sizeof(ParseContext1),
 179     NULL,
 180     mpegvideo_parse,
 181     ff_parse1_close,
 182 };