git.sesse.net Git - ffmpeg/blob - libavcodec/h264_parser.c

   1 /*
   2  * H.26L/H.264/AVC/JVT/14496-10/... parser
   3  * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
   4  *
   5  * This file is part of Libav.
   6  *
   7  * Libav is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * Libav is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with Libav; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file
  24  * H.264 / AVC / MPEG4 part10 parser.
  25  * @author Michael Niedermayer <michaelni@gmx.at>
  26  */
  27
  28 #include "libavutil/attributes.h"
  29 #include "parser.h"
  30 #include "h264data.h"
  31 #include "golomb.h"
  32 #include "internal.h"
  33
  34 #include <assert.h>
  35
  36
  37 static int h264_find_frame_end(H264Context *h, const uint8_t *buf,
  38                                int buf_size)
  39 {
  40     int i;
  41     uint32_t state;
  42     ParseContext *pc = &h->parse_context;
  43 //    mb_addr= pc->mb_addr - 1;
  44     state = pc->state;
  45     if (state > 13)
  46         state = 7;
  47
  48     for (i = 0; i < buf_size; i++) {
  49         if (state == 7) {
  50             i += h->h264dsp.h264_find_start_code_candidate(buf + i, buf_size - i);
  51             if (i < buf_size)
  52                 state = 2;
  53         } else if (state <= 2) {
  54             if (buf[i] == 1)
  55                 state ^= 5;            // 2->7, 1->4, 0->5
  56             else if (buf[i])
  57                 state = 7;
  58             else
  59                 state >>= 1;           // 2->1, 1->0, 0->0
  60         } else if (state <= 5) {
  61             int v = buf[i] & 0x1F;
  62             if (v == 6 || v == 7 || v == 8 || v == 9) {
  63                 if (pc->frame_start_found) {
  64                     i++;
  65                     goto found;
  66                 }
  67             } else if (v == 1 || v == 2 || v == 5) {
  68                 if (pc->frame_start_found) {
  69                     state += 8;
  70                     continue;
  71                 } else
  72                     pc->frame_start_found = 1;
  73             }
  74             state = 7;
  75         } else {
  76             if (buf[i] & 0x80)
  77                 goto found;
  78             state = 7;
  79         }
  80     }
  81     pc->state = state;
  82     return END_NOT_FOUND;
  83
  84 found:
  85     pc->state             = 7;
  86     pc->frame_start_found = 0;
  87     return i - (state & 5);
  88 }
  89
  90 /**
  91  * Parse NAL units of found picture and decode some basic information.
  92  *
  93  * @param s parser context.
  94  * @param avctx codec context.
  95  * @param buf buffer with field/frame data.
  96  * @param buf_size size of the buffer.
  97  */
  98 static inline int parse_nal_units(AVCodecParserContext *s,
  99                                   AVCodecContext *avctx,
 100                                   const uint8_t *buf, int buf_size)
 101 {
 102     H264Context *h         = s->priv_data;
 103     const uint8_t *buf_end = buf + buf_size;
 104     unsigned int pps_id;
 105     unsigned int slice_type;
 106     int state = -1;
 107     const uint8_t *ptr;
 108     int field_poc[2];
 109
 110     /* set some sane default values */
 111     s->pict_type         = AV_PICTURE_TYPE_I;
 112     s->key_frame         = 0;
 113     s->picture_structure = AV_PICTURE_STRUCTURE_UNKNOWN;
 114
 115     h->avctx                        = avctx;
 116     h->sei_recovery_frame_cnt       = -1;
 117     h->sei_dpb_output_delay         = 0;
 118     h->sei_cpb_removal_delay        = -1;
 119     h->sei_buffering_period_present = 0;
 120
 121     if (!buf_size)
 122         return 0;
 123
 124     for (;;) {
 125         int src_length, dst_length, consumed;
 126         buf = avpriv_find_start_code(buf, buf_end, &state);
 127         if (buf >= buf_end)
 128             break;
 129         --buf;
 130         src_length = buf_end - buf;
 131         switch (state & 0x1f) {
 132         case NAL_SLICE:
 133         case NAL_IDR_SLICE:
 134             // Do not walk the whole buffer just to decode slice header
 135             if (src_length > 20)
 136                 src_length = 20;
 137             break;
 138         }
 139         ptr = ff_h264_decode_nal(h, buf, &dst_length, &consumed, src_length);
 140         if (ptr == NULL || dst_length < 0)
 141             break;
 142
 143         init_get_bits(&h->gb, ptr, 8 * dst_length);
 144         switch (h->nal_unit_type) {
 145         case NAL_SPS:
 146             ff_h264_decode_seq_parameter_set(h);
 147             break;
 148         case NAL_PPS:
 149             ff_h264_decode_picture_parameter_set(h, h->gb.size_in_bits);
 150             break;
 151         case NAL_SEI:
 152             ff_h264_decode_sei(h);
 153             break;
 154         case NAL_IDR_SLICE:
 155             s->key_frame = 1;
 156
 157             h->prev_frame_num        = 0;
 158             h->prev_frame_num_offset = 0;
 159             h->prev_poc_msb          =
 160             h->prev_poc_lsb          = 0;
 161         /* fall through */
 162         case NAL_SLICE:
 163             get_ue_golomb(&h->gb);  // skip first_mb_in_slice
 164             slice_type   = get_ue_golomb_31(&h->gb);
 165             s->pict_type = golomb_to_pict_type[slice_type % 5];
 166             if (h->sei_recovery_frame_cnt >= 0) {
 167                 /* key frame, since recovery_frame_cnt is set */
 168                 s->key_frame = 1;
 169             }
 170             pps_id = get_ue_golomb(&h->gb);
 171             if (pps_id >= MAX_PPS_COUNT) {
 172                 av_log(h->avctx, AV_LOG_ERROR,
 173                        "pps_id out of range\n");
 174                 return -1;
 175             }
 176             if (!h->pps_buffers[pps_id]) {
 177                 av_log(h->avctx, AV_LOG_ERROR,
 178                        "non-existing PPS referenced\n");
 179                 return -1;
 180             }
 181             h->pps = *h->pps_buffers[pps_id];
 182             if (!h->sps_buffers[h->pps.sps_id]) {
 183                 av_log(h->avctx, AV_LOG_ERROR,
 184                        "non-existing SPS referenced\n");
 185                 return -1;
 186             }
 187             h->sps       = *h->sps_buffers[h->pps.sps_id];
 188             h->frame_num = get_bits(&h->gb, h->sps.log2_max_frame_num);
 189
 190             avctx->profile = ff_h264_get_profile(&h->sps);
 191             avctx->level   = h->sps.level_idc;
 192
 193             if (h->sps.frame_mbs_only_flag) {
 194                 h->picture_structure = PICT_FRAME;
 195             } else {
 196                 if (get_bits1(&h->gb)) { // field_pic_flag
 197                     h->picture_structure = PICT_TOP_FIELD + get_bits1(&h->gb); // bottom_field_flag
 198                 } else {
 199                     h->picture_structure = PICT_FRAME;
 200                 }
 201             }
 202
 203             if (h->nal_unit_type == NAL_IDR_SLICE)
 204                 get_ue_golomb(&h->gb); /* idr_pic_id */
 205             if (h->sps.poc_type == 0) {
 206                 h->poc_lsb = get_bits(&h->gb, h->sps.log2_max_poc_lsb);
 207
 208                 if (h->pps.pic_order_present == 1 &&
 209                     h->picture_structure == PICT_FRAME)
 210                     h->delta_poc_bottom = get_se_golomb(&h->gb);
 211             }
 212
 213             if (h->sps.poc_type == 1 &&
 214                 !h->sps.delta_pic_order_always_zero_flag) {
 215                 h->delta_poc[0] = get_se_golomb(&h->gb);
 216
 217                 if (h->pps.pic_order_present == 1 &&
 218                     h->picture_structure == PICT_FRAME)
 219                     h->delta_poc[1] = get_se_golomb(&h->gb);
 220             }
 221
 222             ff_init_poc(h, field_poc, &s->output_picture_number);
 223
 224             if (h->sps.pic_struct_present_flag) {
 225                 switch (h->sei_pic_struct) {
 226                 case SEI_PIC_STRUCT_TOP_FIELD:
 227                 case SEI_PIC_STRUCT_BOTTOM_FIELD:
 228                     s->repeat_pict = 0;
 229                     break;
 230                 case SEI_PIC_STRUCT_FRAME:
 231                 case SEI_PIC_STRUCT_TOP_BOTTOM:
 232                 case SEI_PIC_STRUCT_BOTTOM_TOP:
 233                     s->repeat_pict = 1;
 234                     break;
 235                 case SEI_PIC_STRUCT_TOP_BOTTOM_TOP:
 236                 case SEI_PIC_STRUCT_BOTTOM_TOP_BOTTOM:
 237                     s->repeat_pict = 2;
 238                     break;
 239                 case SEI_PIC_STRUCT_FRAME_DOUBLING:
 240                     s->repeat_pict = 3;
 241                     break;
 242                 case SEI_PIC_STRUCT_FRAME_TRIPLING:
 243                     s->repeat_pict = 5;
 244                     break;
 245                 default:
 246                     s->repeat_pict = h->picture_structure == PICT_FRAME ? 1 : 0;
 247                     break;
 248                 }
 249             } else {
 250                 s->repeat_pict = h->picture_structure == PICT_FRAME ? 1 : 0;
 251             }
 252
 253             if (h->picture_structure == PICT_FRAME) {
 254                 s->picture_structure = AV_PICTURE_STRUCTURE_FRAME;
 255                 if (h->sps.pic_struct_present_flag) {
 256                     switch (h->sei_pic_struct) {
 257                     case SEI_PIC_STRUCT_TOP_BOTTOM:
 258                     case SEI_PIC_STRUCT_TOP_BOTTOM_TOP:
 259                         s->field_order = AV_FIELD_TT;
 260                         break;
 261                     case SEI_PIC_STRUCT_BOTTOM_TOP:
 262                     case SEI_PIC_STRUCT_BOTTOM_TOP_BOTTOM:
 263                         s->field_order = AV_FIELD_BB;
 264                         break;
 265                     default:
 266                         s->field_order = AV_FIELD_PROGRESSIVE;
 267                         break;
 268                     }
 269                 } else {
 270                     if (field_poc[0] < field_poc[1])
 271                         s->field_order = AV_FIELD_TT;
 272                     else if (field_poc[0] > field_poc[1])
 273                         s->field_order = AV_FIELD_BB;
 274                     else
 275                         s->field_order = AV_FIELD_PROGRESSIVE;
 276                 }
 277             } else {
 278                 if (h->picture_structure == PICT_TOP_FIELD)
 279                     s->picture_structure = AV_PICTURE_STRUCTURE_TOP_FIELD;
 280                 else
 281                     s->picture_structure = AV_PICTURE_STRUCTURE_BOTTOM_FIELD;
 282                 s->field_order = AV_FIELD_UNKNOWN;
 283             }
 284
 285             return 0; /* no need to evaluate the rest */
 286         }
 287         buf += consumed;
 288     }
 289     /* didn't find a picture! */
 290     av_log(h->avctx, AV_LOG_ERROR, "missing picture in access unit\n");
 291     return -1;
 292 }
 293
 294 static int h264_parse(AVCodecParserContext *s,
 295                       AVCodecContext *avctx,
 296                       const uint8_t **poutbuf, int *poutbuf_size,
 297                       const uint8_t *buf, int buf_size)
 298 {
 299     H264Context *h   = s->priv_data;
 300     ParseContext *pc = &h->parse_context;
 301     int next;
 302
 303     if (!h->got_first) {
 304         h->got_first = 1;
 305         if (avctx->extradata_size) {
 306             h->avctx = avctx;
 307             // must be done like in the decoder.
 308             // otherwise opening the parser, creating extradata,
 309             // and then closing and opening again
 310             // will cause has_b_frames to be always set.
 311             // NB: estimate_timings_from_pts behaves exactly like this.
 312             if (!avctx->has_b_frames)
 313                 h->low_delay = 1;
 314             ff_h264_decode_extradata(h);
 315         }
 316     }
 317
 318     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
 319         next = buf_size;
 320     } else {
 321         next = h264_find_frame_end(h, buf, buf_size);
 322
 323         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 324             *poutbuf      = NULL;
 325             *poutbuf_size = 0;
 326             return buf_size;
 327         }
 328
 329         if (next < 0 && next != END_NOT_FOUND) {
 330             assert(pc->last_index + next >= 0);
 331             h264_find_frame_end(h, &pc->buffer[pc->last_index + next], -next); // update state
 332         }
 333     }
 334
 335     parse_nal_units(s, avctx, buf, buf_size);
 336
 337     if (h->sei_cpb_removal_delay >= 0) {
 338         s->dts_sync_point    = h->sei_buffering_period_present;
 339         s->dts_ref_dts_delta = h->sei_cpb_removal_delay;
 340         s->pts_dts_delta     = h->sei_dpb_output_delay;
 341     } else {
 342         s->dts_sync_point    = INT_MIN;
 343         s->dts_ref_dts_delta = INT_MIN;
 344         s->pts_dts_delta     = INT_MIN;
 345     }
 346
 347     if (s->flags & PARSER_FLAG_ONCE) {
 348         s->flags &= PARSER_FLAG_COMPLETE_FRAMES;
 349     }
 350
 351     *poutbuf      = buf;
 352     *poutbuf_size = buf_size;
 353     return next;
 354 }
 355
 356 static int h264_split(AVCodecContext *avctx,
 357                       const uint8_t *buf, int buf_size)
 358 {
 359     int i;
 360     uint32_t state = -1;
 361     int has_sps    = 0;
 362
 363     for (i = 0; i <= buf_size; i++) {
 364         if ((state & 0xFFFFFF1F) == 0x107)
 365             has_sps = 1;
 366         /*  if((state&0xFFFFFF1F) == 0x101 ||
 367          *     (state&0xFFFFFF1F) == 0x102 ||
 368          *     (state&0xFFFFFF1F) == 0x105) {
 369          *  }
 370          */
 371         if ((state & 0xFFFFFF00) == 0x100 && (state & 0xFFFFFF1F) != 0x107 &&
 372             (state & 0xFFFFFF1F) != 0x108 && (state & 0xFFFFFF1F) != 0x109) {
 373             if (has_sps) {
 374                 while (i > 4 && buf[i - 5] == 0)
 375                     i--;
 376                 return i - 4;
 377             }
 378         }
 379         if (i < buf_size)
 380             state = (state << 8) | buf[i];
 381     }
 382     return 0;
 383 }
 384
 385 static void close(AVCodecParserContext *s)
 386 {
 387     H264Context *h   = s->priv_data;
 388     ParseContext *pc = &h->parse_context;
 389
 390     av_free(pc->buffer);
 391     ff_h264_free_context(h);
 392 }
 393
 394 static av_cold int init(AVCodecParserContext *s)
 395 {
 396     H264Context *h = s->priv_data;
 397     h->thread_context[0]   = h;
 398     h->slice_context_count = 1;
 399     ff_h264dsp_init(&h->h264dsp, 8, 1);
 400     return 0;
 401 }
 402
 403 AVCodecParser ff_h264_parser = {
 404     .codec_ids      = { AV_CODEC_ID_H264 },
 405     .priv_data_size = sizeof(H264Context),
 406     .parser_init    = init,
 407     .parser_parse   = h264_parse,
 408     .parser_close   = close,
 409     .split          = h264_split,
 410 };