libavcodec/mpegvideo_parser.c

   1 /*
   2  * MPEG-1 / MPEG-2 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 "libavutil/avassert.h"
  24 #include "decode.h"
  25 #include "parser.h"
  26 #include "mpeg12.h"
  27 #include "mpeg12data.h"
  28 #include "parser_internal.h"
  29 #include "startcode.h"
  30
  31 struct MpvParseContext {
  32     ParseContext pc;
  33     AVRational frame_rate;
  34     int progressive_sequence;
  35     int width, height;
  36 };
  37
  38 /**
  39  * Find the end of the current frame in the bitstream.
  40  * @return the position of the first byte of the next frame, or -1
  41  */
  42 static int mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf,
  43                                 int buf_size, AVCodecParserContext *s)
  44 {
  45     int i;
  46     uint32_t state = pc->state;
  47
  48     /* EOF considered as end of frame */
  49     if (buf_size == 0)
  50         return 0;
  51
  52 /*
  53  0  frame start         -> 1/4
  54  1  first_SEQEXT        -> 0/2
  55  2  first field start   -> 3/0
  56  3  second_SEQEXT       -> 2/0
  57  4  searching end
  58 */
  59
  60     for (i = 0; i < buf_size; i++) {
  61         av_assert1(pc->frame_start_found >= 0 && pc->frame_start_found <= 4);
  62         if (pc->frame_start_found & 1) {
  63             if (state == EXT_START_CODE && (buf[i] & 0xF0) != 0x80)
  64                 pc->frame_start_found--;
  65             else if (state == EXT_START_CODE + 2) {
  66                 if ((buf[i] & 3) == 3)
  67                     pc->frame_start_found = 0;
  68                 else
  69                     pc->frame_start_found = (pc->frame_start_found + 1) & 3;
  70             }
  71             state++;
  72         } else {
  73             i = avpriv_find_start_code(buf + i, buf + buf_size, &state) - buf - 1;
  74             if (pc->frame_start_found == 0 && state >= SLICE_MIN_START_CODE && state <= SLICE_MAX_START_CODE) {
  75                 i++;
  76                 pc->frame_start_found = 4;
  77             }
  78             if (state == SEQ_END_CODE) {
  79                 pc->frame_start_found = 0;
  80                 pc->state = -1;
  81                 return i + 1;
  82             }
  83             if (pc->frame_start_found == 2 && state == SEQ_START_CODE)
  84                 pc->frame_start_found = 0;
  85             if (pc->frame_start_found  < 4 && state == EXT_START_CODE)
  86                 pc->frame_start_found++;
  87             if (pc->frame_start_found == 4 && (state & 0xFFFFFF00) == 0x100) {
  88                 if (state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE) {
  89                     pc->frame_start_found = 0;
  90                     pc->state             = -1;
  91                     return i - 3;
  92                 }
  93             }
  94             if (pc->frame_start_found == 0 && s && state == PICTURE_START_CODE) {
  95                 ff_fetch_timestamp(s, i - 3, 1, i > 3);
  96             }
  97         }
  98     }
  99     pc->state = state;
 100     return END_NOT_FOUND;
 101 }
 102
 103 static void mpegvideo_extract_headers(AVCodecParserContext *s,
 104                                       AVCodecContext *avctx,
 105                                       const uint8_t *buf, int buf_size)
 106 {
 107     struct MpvParseContext *pc = s->priv_data;
 108     const uint8_t *buf_end = buf + buf_size;
 109     int bytes_left;
 110     int did_set_size=0;
 111     int set_dim_ret = 0;
 112     int bit_rate = 0;
 113     int vbv_delay = 0;
 114     enum AVPixelFormat pix_fmt = AV_PIX_FMT_NONE;
 115
 116     // number of picture coding extensions (i.e. MPEG2 pictures)
 117     // in this packet - should be 1 or 2
 118     int nb_pic_ext = 0;
 119     // when there are two pictures in the packet this indicates
 120     // which field is in the first of them
 121     int first_field = AV_FIELD_UNKNOWN;
 122
 123 //FIXME replace the crap with get_bits()
 124     while (buf < buf_end) {
 125         uint32_t start_code = -1;
 126         buf= avpriv_find_start_code(buf, buf_end, &start_code);
 127         bytes_left = buf_end - buf;
 128         switch(start_code) {
 129         case PICTURE_START_CODE:
 130             if (bytes_left >= 2) {
 131                 s->pict_type = (buf[1] >> 3) & 7;
 132                 if (bytes_left >= 4)
 133                     vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3] >> 3);
 134             }
 135             break;
 136         case SEQ_START_CODE:
 137             if (bytes_left >= 7) {
 138                 int frame_rate_index;
 139
 140                 pc->width  = (buf[0] << 4) | (buf[1] >> 4);
 141                 pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
 142                 if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
 143                     set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
 144                     did_set_size=1;
 145                 }
 146                 pix_fmt = AV_PIX_FMT_YUV420P;
 147                 frame_rate_index = buf[3] & 0xf;
 148                 pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
 149                 bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
 150                 avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
 151             }
 152             break;
 153         case EXT_START_CODE:
 154             if (bytes_left >= 1) {
 155                 switch (buf[0] >> 4) { // ext_type
 156                 case 0x1: /* sequence extension */
 157                     if (bytes_left >= 6) {
 158                         int horiz_size_ext   = ((buf[1] & 1) << 1) | (buf[2] >> 7);
 159                         int  vert_size_ext   = (buf[2] >> 5) & 3;
 160                         int   bit_rate_ext   = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
 161                         int frame_rate_ext_n = (buf[5] >> 5) & 3;
 162                         int frame_rate_ext_d = (buf[5] & 0x1f);
 163                         pc->progressive_sequence = buf[1] & (1 << 3);
 164                         avctx->has_b_frames= !(buf[5] >> 7);
 165
 166                         switch ((buf[1] >> 1) & 3) { // chroma_format
 167                         case 1: pix_fmt = AV_PIX_FMT_YUV420P; break;
 168                         case 2: pix_fmt = AV_PIX_FMT_YUV422P; break;
 169                         case 3: pix_fmt = AV_PIX_FMT_YUV444P; break;
 170                         }
 171
 172                         pc->width  = (pc->width & 0xFFF) | (horiz_size_ext << 12);
 173                         pc->height = (pc->height& 0xFFF) | ( vert_size_ext << 12);
 174                         bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
 175                         if(did_set_size)
 176                             set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
 177                         avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1);
 178                         avctx->framerate.den = pc->frame_rate.den * (frame_rate_ext_d + 1);
 179                         avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
 180                     }
 181                     break;
 182                 case 0x8: /* picture coding extension */
 183                     if (bytes_left >= 5) {
 184                         int    top_field_first = buf[3] & (1 << 7);
 185                         int repeat_first_field = buf[3] & (1 << 1);
 186                         int  progressive_frame = buf[4] & (1 << 7);
 187
 188                         /* check if we must repeat the frame */
 189                         s->repeat_pict = 1;
 190                         if (repeat_first_field) {
 191                             if (pc->progressive_sequence) {
 192                                 if (top_field_first)
 193                                     s->repeat_pict = 5;
 194                                 else
 195                                     s->repeat_pict = 3;
 196                             } else if (progressive_frame) {
 197                                 s->repeat_pict = 2;
 198                             }
 199                         }
 200
 201                         if (!pc->progressive_sequence && !progressive_frame) {
 202                             if (top_field_first)
 203                                 s->field_order = AV_FIELD_TT;
 204                             else
 205                                 s->field_order = AV_FIELD_BB;
 206                         } else
 207                             s->field_order = AV_FIELD_PROGRESSIVE;
 208
 209                         s->picture_structure = buf[2] & 3;
 210
 211                         if (!nb_pic_ext) {
 212                             // remember parity of the first field for the case
 213                             // when there are 2 fields in packet
 214                             switch (s->picture_structure) {
 215                             case AV_PICTURE_STRUCTURE_BOTTOM_FIELD: first_field = AV_FIELD_BB; break;
 216                             case AV_PICTURE_STRUCTURE_TOP_FIELD:    first_field = AV_FIELD_TT; break;
 217                             }
 218                         }
 219
 220                         nb_pic_ext++;
 221                     }
 222                     break;
 223                 }
 224             }
 225             break;
 226         case -1:
 227             goto the_end;
 228         default:
 229             /* we stop parsing when we encounter a slice. It ensures
 230                that this function takes a negligible amount of time */
 231             if (start_code >= SLICE_MIN_START_CODE &&
 232                 start_code <= SLICE_MAX_START_CODE)
 233                 goto the_end;
 234             break;
 235         }
 236     }
 237  the_end:
 238     if (set_dim_ret < 0)
 239         av_log(avctx, AV_LOG_ERROR, "Failed to set dimensions\n");
 240
 241     if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate && bit_rate != 0x3FFFF) {
 242         avctx->rc_max_rate = 400LL*bit_rate;
 243     }
 244     if (bit_rate &&
 245         ((avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate != 0x3FFFF) || vbv_delay != 0xFFFF)) {
 246         avctx->bit_rate = 400LL*bit_rate;
 247     }
 248
 249     if (pix_fmt != AV_PIX_FMT_NONE) {
 250         s->format = pix_fmt;
 251         s->width  = pc->width;
 252         s->height = pc->height;
 253         s->coded_width  = FFALIGN(pc->width,  16);
 254         s->coded_height = FFALIGN(pc->height, 16);
 255     }
 256
 257     if (avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO || nb_pic_ext > 1) {
 258         s->repeat_pict       = 1;
 259         s->picture_structure = AV_PICTURE_STRUCTURE_FRAME;
 260         s->field_order       = nb_pic_ext > 1 ? first_field : AV_FIELD_PROGRESSIVE;
 261     }
 262 }
 263
 264 static int mpegvideo_parse(AVCodecParserContext *s,
 265                            AVCodecContext *avctx,
 266                            const uint8_t **poutbuf, int *poutbuf_size,
 267                            const uint8_t *buf, int buf_size)
 268 {
 269     struct MpvParseContext *pc1 = s->priv_data;
 270     ParseContext *pc= &pc1->pc;
 271     int next;
 272
 273     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
 274         next= buf_size;
 275     }else{
 276         next = mpeg1_find_frame_end(pc, buf, buf_size, s);
 277
 278         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 279             *poutbuf = NULL;
 280             *poutbuf_size = 0;
 281             return buf_size;
 282         }
 283
 284     }
 285     /* we have a full frame : we just parse the first few MPEG headers
 286        to have the full timing information. The time take by this
 287        function should be negligible for uncorrupted streams */
 288     mpegvideo_extract_headers(s, avctx, buf, buf_size);
 289     ff_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
 290             s->pict_type, av_q2d(avctx->framerate), s->repeat_pict);
 291
 292     *poutbuf = buf;
 293     *poutbuf_size = buf_size;
 294     return next;
 295 }
 296
 297 static av_cold int mpegvideo_parse_init(AVCodecParserContext *s)
 298 {
 299     s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
 300     return 0;
 301 }
 302
 303 const FFCodecParser ff_mpegvideo_parser = {
 304     PARSER_CODEC_LIST(AV_CODEC_ID_MPEG1VIDEO, AV_CODEC_ID_MPEG2VIDEO),
 305     .priv_data_size = sizeof(struct MpvParseContext),
 306     .init           = mpegvideo_parse_init,
 307     .parse          = mpegvideo_parse,
 308     .close          = ff_parse_close,
 309 };