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 "internal.h"
  24 #include "parser.h"
  25 #include "mpeg12.h"
  26 #include "mpeg12data.h"
  27 #include "startcode.h"
  28
  29 struct MpvParseContext {
  30     ParseContext pc;
  31     AVRational frame_rate;
  32     int progressive_sequence;
  33     int width, height;
  34 };
  35
  36 #if !FF_API_FLAG_TRUNCATED
  37 /**
  38  * Find the end of the current frame in the bitstream.
  39  * @return the position of the first byte of the next frame, or -1
  40  */
  41 static int mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf,
  42                                 int buf_size, AVCodecParserContext *s)
  43 {
  44     int i;
  45     uint32_t state = pc->state;
  46
  47     /* EOF considered as end of frame */
  48     if (buf_size == 0)
  49         return 0;
  50
  51 /*
  52  0  frame start         -> 1/4
  53  1  first_SEQEXT        -> 0/2
  54  2  first field start   -> 3/0
  55  3  second_SEQEXT       -> 2/0
  56  4  searching end
  57 */
  58
  59     for (i = 0; i < buf_size; i++) {
  60         av_assert1(pc->frame_start_found >= 0 && pc->frame_start_found <= 4);
  61         if (pc->frame_start_found & 1) {
  62             if (state == EXT_START_CODE && (buf[i] & 0xF0) != 0x80)
  63                 pc->frame_start_found--;
  64             else if (state == EXT_START_CODE + 2) {
  65                 if ((buf[i] & 3) == 3)
  66                     pc->frame_start_found = 0;
  67                 else
  68                     pc->frame_start_found = (pc->frame_start_found + 1) & 3;
  69             }
  70             state++;
  71         } else {
  72             i = avpriv_find_start_code(buf + i, buf + buf_size, &state) - buf - 1;
  73             if (pc->frame_start_found == 0 && state >= SLICE_MIN_START_CODE && state <= SLICE_MAX_START_CODE) {
  74                 i++;
  75                 pc->frame_start_found = 4;
  76             }
  77             if (state == SEQ_END_CODE) {
  78                 pc->frame_start_found = 0;
  79                 pc->state = -1;
  80                 return i + 1;
  81             }
  82             if (pc->frame_start_found == 2 && state == SEQ_START_CODE)
  83                 pc->frame_start_found = 0;
  84             if (pc->frame_start_found  < 4 && state == EXT_START_CODE)
  85                 pc->frame_start_found++;
  86             if (pc->frame_start_found == 4 && (state & 0xFFFFFF00) == 0x100) {
  87                 if (state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE) {
  88                     pc->frame_start_found = 0;
  89                     pc->state             = -1;
  90                     return i - 3;
  91                 }
  92             }
  93             if (pc->frame_start_found == 0 && s && state == PICTURE_START_CODE) {
  94                 ff_fetch_timestamp(s, i - 3, 1, i > 3);
  95             }
  96         }
  97     }
  98     pc->state = state;
  99     return END_NOT_FOUND;
 100 }
 101 #endif
 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     uint32_t start_code;
 110     int frame_rate_index, ext_type, bytes_left;
 111     int frame_rate_ext_n, frame_rate_ext_d;
 112     int top_field_first, repeat_first_field, progressive_frame;
 113     int horiz_size_ext, vert_size_ext, bit_rate_ext;
 114     int did_set_size=0;
 115     int set_dim_ret = 0;
 116     int bit_rate = 0;
 117     int vbv_delay = 0;
 118     int chroma_format;
 119     enum AVPixelFormat pix_fmt = AV_PIX_FMT_NONE;
 120 //FIXME replace the crap with get_bits()
 121     s->repeat_pict = 0;
 122
 123     while (buf < buf_end) {
 124         start_code= -1;
 125         buf= avpriv_find_start_code(buf, buf_end, &start_code);
 126         bytes_left = buf_end - buf;
 127         switch(start_code) {
 128         case PICTURE_START_CODE:
 129             if (bytes_left >= 2) {
 130                 s->pict_type = (buf[1] >> 3) & 7;
 131                 if (bytes_left >= 4)
 132                     vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3] >> 3);
 133             }
 134             break;
 135         case SEQ_START_CODE:
 136             if (bytes_left >= 7) {
 137                 pc->width  = (buf[0] << 4) | (buf[1] >> 4);
 138                 pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
 139                 if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
 140                     set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
 141                     did_set_size=1;
 142                 }
 143                 pix_fmt = AV_PIX_FMT_YUV420P;
 144                 frame_rate_index = buf[3] & 0xf;
 145                 pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
 146                 bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
 147                 avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
 148                 avctx->ticks_per_frame = 1;
 149             }
 150             break;
 151         case EXT_START_CODE:
 152             if (bytes_left >= 1) {
 153                 ext_type = (buf[0] >> 4);
 154                 switch(ext_type) {
 155                 case 0x1: /* sequence extension */
 156                     if (bytes_left >= 6) {
 157                         horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
 158                         vert_size_ext = (buf[2] >> 5) & 3;
 159                         bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
 160                         frame_rate_ext_n = (buf[5] >> 5) & 3;
 161                         frame_rate_ext_d = (buf[5] & 0x1f);
 162                         pc->progressive_sequence = buf[1] & (1 << 3);
 163                         avctx->has_b_frames= !(buf[5] >> 7);
 164
 165                         chroma_format = (buf[1] >> 1) & 3;
 166                         switch (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                         avctx->ticks_per_frame = 2;
 181                     }
 182                     break;
 183                 case 0x8: /* picture coding extension */
 184                     if (bytes_left >= 5) {
 185                         top_field_first = buf[3] & (1 << 7);
 186                         repeat_first_field = buf[3] & (1 << 1);
 187                         progressive_frame = buf[4] & (1 << 7);
 188
 189                         /* check if we must repeat the frame */
 190                         s->repeat_pict = 1;
 191                         if (repeat_first_field) {
 192                             if (pc->progressive_sequence) {
 193                                 if (top_field_first)
 194                                     s->repeat_pict = 5;
 195                                 else
 196                                     s->repeat_pict = 3;
 197                             } else if (progressive_frame) {
 198                                 s->repeat_pict = 2;
 199                             }
 200                         }
 201
 202                         if (!pc->progressive_sequence && !progressive_frame) {
 203                             if (top_field_first)
 204                                 s->field_order = AV_FIELD_TT;
 205                             else
 206                                 s->field_order = AV_FIELD_BB;
 207                         } else
 208                             s->field_order = AV_FIELD_PROGRESSIVE;
 209                     }
 210                     break;
 211                 }
 212             }
 213             break;
 214         case -1:
 215             goto the_end;
 216         default:
 217             /* we stop parsing when we encounter a slice. It ensures
 218                that this function takes a negligible amount of time */
 219             if (start_code >= SLICE_MIN_START_CODE &&
 220                 start_code <= SLICE_MAX_START_CODE)
 221                 goto the_end;
 222             break;
 223         }
 224     }
 225  the_end:
 226     if (set_dim_ret < 0)
 227         av_log(avctx, AV_LOG_ERROR, "Failed to set dimensions\n");
 228
 229     if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate) {
 230         avctx->rc_max_rate = 400LL*bit_rate;
 231     }
 232     if (bit_rate &&
 233         ((avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate != 0x3FFFF) || vbv_delay != 0xFFFF)) {
 234         avctx->bit_rate = 400LL*bit_rate;
 235     }
 236
 237     if (pix_fmt != AV_PIX_FMT_NONE) {
 238         s->format = pix_fmt;
 239         s->width  = pc->width;
 240         s->height = pc->height;
 241         s->coded_width  = FFALIGN(pc->width,  16);
 242         s->coded_height = FFALIGN(pc->height, 16);
 243     }
 244
 245 #if FF_API_AVCTX_TIMEBASE
 246     if (avctx->framerate.num)
 247         avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
 248 #endif
 249 }
 250
 251 static int mpegvideo_parse(AVCodecParserContext *s,
 252                            AVCodecContext *avctx,
 253                            const uint8_t **poutbuf, int *poutbuf_size,
 254                            const uint8_t *buf, int buf_size)
 255 {
 256     struct MpvParseContext *pc1 = s->priv_data;
 257     ParseContext *pc= &pc1->pc;
 258     int next;
 259
 260     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
 261         next= buf_size;
 262     }else{
 263 #if FF_API_FLAG_TRUNCATED
 264         next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
 265 #else
 266         next = mpeg1_find_frame_end(pc, buf, buf_size, s);
 267 #endif
 268
 269         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 270             *poutbuf = NULL;
 271             *poutbuf_size = 0;
 272             return buf_size;
 273         }
 274
 275     }
 276     /* we have a full frame : we just parse the first few MPEG headers
 277        to have the full timing information. The time take by this
 278        function should be negligible for uncorrupted streams */
 279     mpegvideo_extract_headers(s, avctx, buf, buf_size);
 280     ff_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
 281             s->pict_type, av_q2d(avctx->framerate), s->repeat_pict);
 282
 283     *poutbuf = buf;
 284     *poutbuf_size = buf_size;
 285     return next;
 286 }
 287
 288 static int mpegvideo_parse_init(AVCodecParserContext *s)
 289 {
 290     s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
 291     return 0;
 292 }
 293
 294 const AVCodecParser ff_mpegvideo_parser = {
 295     .codec_ids      = { AV_CODEC_ID_MPEG1VIDEO, AV_CODEC_ID_MPEG2VIDEO },
 296     .priv_data_size = sizeof(struct MpvParseContext),
 297     .parser_init    = mpegvideo_parse_init,
 298     .parser_parse   = mpegvideo_parse,
 299     .parser_close   = ff_parse_close,
 300 };