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 Libav.
   7  *
   8  * Libav 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  * Libav 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 Libav; 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 struct MpvParseContext {
  27     ParseContext pc;
  28     AVRational frame_rate;
  29     int progressive_sequence;
  30     int width, height;
  31 };
  32
  33
  34 static void mpegvideo_extract_headers(AVCodecParserContext *s,
  35                                       AVCodecContext *avctx,
  36                                       const uint8_t *buf, int buf_size)
  37 {
  38     struct MpvParseContext *pc = s->priv_data;
  39     const uint8_t *buf_end = buf + buf_size;
  40     uint32_t start_code;
  41     int frame_rate_index, ext_type, bytes_left;
  42     int frame_rate_ext_n, frame_rate_ext_d;
  43     int top_field_first, repeat_first_field, progressive_frame;
  44     int horiz_size_ext, vert_size_ext, bit_rate_ext;
  45     int did_set_size=0;
  46 //FIXME replace the crap with get_bits()
  47     s->repeat_pict = 0;
  48
  49     while (buf < buf_end) {
  50         start_code= -1;
  51         buf= avpriv_mpv_find_start_code(buf, buf_end, &start_code);
  52         bytes_left = buf_end - buf;
  53         switch(start_code) {
  54         case PICTURE_START_CODE:
  55             if (bytes_left >= 2) {
  56                 s->pict_type = (buf[1] >> 3) & 7;
  57             }
  58             break;
  59         case SEQ_START_CODE:
  60             if (bytes_left >= 7) {
  61                 pc->width  = (buf[0] << 4) | (buf[1] >> 4);
  62                 pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
  63                 if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
  64                     avcodec_set_dimensions(avctx, pc->width, pc->height);
  65                     did_set_size=1;
  66                 }
  67                 frame_rate_index = buf[3] & 0xf;
  68                 pc->frame_rate.den = avctx->time_base.den = ff_mpeg12_frame_rate_tab[frame_rate_index].num;
  69                 pc->frame_rate.num = avctx->time_base.num = ff_mpeg12_frame_rate_tab[frame_rate_index].den;
  70                 avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
  71                 avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
  72             }
  73             break;
  74         case EXT_START_CODE:
  75             if (bytes_left >= 1) {
  76                 ext_type = (buf[0] >> 4);
  77                 switch(ext_type) {
  78                 case 0x1: /* sequence extension */
  79                     if (bytes_left >= 6) {
  80                         horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
  81                         vert_size_ext = (buf[2] >> 5) & 3;
  82                         bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
  83                         frame_rate_ext_n = (buf[5] >> 5) & 3;
  84                         frame_rate_ext_d = (buf[5] & 0x1f);
  85                         pc->progressive_sequence = buf[1] & (1 << 3);
  86                         avctx->has_b_frames= !(buf[5] >> 7);
  87
  88                         pc->width  |=(horiz_size_ext << 12);
  89                         pc->height |=( vert_size_ext << 12);
  90                         avctx->bit_rate += (bit_rate_ext << 18) * 400;
  91                         if(did_set_size)
  92                             avcodec_set_dimensions(avctx, pc->width, pc->height);
  93                         avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
  94                         avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
  95                         avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
  96                     }
  97                     break;
  98                 case 0x8: /* picture coding extension */
  99                     if (bytes_left >= 5) {
 100                         top_field_first = buf[3] & (1 << 7);
 101                         repeat_first_field = buf[3] & (1 << 1);
 102                         progressive_frame = buf[4] & (1 << 7);
 103
 104                         /* check if we must repeat the frame */
 105                         s->repeat_pict = 1;
 106                         if (repeat_first_field) {
 107                             if (pc->progressive_sequence) {
 108                                 if (top_field_first)
 109                                     s->repeat_pict = 5;
 110                                 else
 111                                     s->repeat_pict = 3;
 112                             } else if (progressive_frame) {
 113                                 s->repeat_pict = 2;
 114                             }
 115                         }
 116                     }
 117                     break;
 118                 }
 119             }
 120             break;
 121         case -1:
 122             goto the_end;
 123         default:
 124             /* we stop parsing when we encounter a slice. It ensures
 125                that this function takes a negligible amount of time */
 126             if (start_code >= SLICE_MIN_START_CODE &&
 127                 start_code <= SLICE_MAX_START_CODE)
 128                 goto the_end;
 129             break;
 130         }
 131     }
 132  the_end: ;
 133 }
 134
 135 static int mpegvideo_parse(AVCodecParserContext *s,
 136                            AVCodecContext *avctx,
 137                            const uint8_t **poutbuf, int *poutbuf_size,
 138                            const uint8_t *buf, int buf_size)
 139 {
 140     struct MpvParseContext *pc1 = s->priv_data;
 141     ParseContext *pc= &pc1->pc;
 142     int next;
 143
 144     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
 145         next= buf_size;
 146     }else{
 147         next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
 148
 149         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 150             *poutbuf = NULL;
 151             *poutbuf_size = 0;
 152             return buf_size;
 153         }
 154
 155     }
 156     /* we have a full frame : we just parse the first few MPEG headers
 157        to have the full timing information. The time take by this
 158        function should be negligible for uncorrupted streams */
 159     mpegvideo_extract_headers(s, avctx, buf, buf_size);
 160     av_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
 161             s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
 162
 163     *poutbuf = buf;
 164     *poutbuf_size = buf_size;
 165     return next;
 166 }
 167
 168 static int mpegvideo_split(AVCodecContext *avctx,
 169                            const uint8_t *buf, int buf_size)
 170 {
 171     int i;
 172     uint32_t state= -1;
 173
 174     for(i=0; i<buf_size; i++){
 175         state= (state<<8) | buf[i];
 176         if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
 177             return i-3;
 178     }
 179     return 0;
 180 }
 181
 182 AVCodecParser ff_mpegvideo_parser = {
 183     .codec_ids      = { AV_CODEC_ID_MPEG1VIDEO, AV_CODEC_ID_MPEG2VIDEO },
 184     .priv_data_size = sizeof(struct MpvParseContext),
 185     .parser_parse   = mpegvideo_parse,
 186     .parser_close   = ff_parse_close,
 187     .split          = mpegvideo_split,
 188 };