libavcodec/dirac_parser.c

   1 /*
   2  * Dirac parser
   3  *
   4  * Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org>
   5  * Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com>
   6  *
   7  * This file is part of Libav.
   8  *
   9  * Libav is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * Libav is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with Libav; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 /**
  25  * @file
  26  * Dirac Parser
  27  * @author Marco Gerards <marco@gnu.org>
  28  */
  29
  30 #include <string.h>
  31
  32 #include "libavutil/intreadwrite.h"
  33 #include "libavutil/mem.h"
  34
  35 #include "parser.h"
  36
  37 #define DIRAC_PARSE_INFO_PREFIX 0x42424344
  38
  39 /**
  40  * Find the end of the current frame in the bitstream.
  41  * @return the position of the first byte of the next frame or -1
  42  */
  43 typedef struct DiracParseContext {
  44     int state;
  45     int is_synced;
  46     int sync_offset;
  47     int header_bytes_needed;
  48     int overread_index;
  49     int buffer_size;
  50     int index;
  51     uint8_t *buffer;
  52     int dirac_unit_size;
  53     uint8_t *dirac_unit;
  54 } DiracParseContext;
  55
  56 static int find_frame_end(DiracParseContext *pc,
  57                           const uint8_t *buf, int buf_size)
  58 {
  59     uint32_t state = pc->state;
  60     int i = 0;
  61
  62     if (!pc->is_synced) {
  63         for (i = 0; i < buf_size; i++) {
  64             state = (state << 8) | buf[i];
  65             if (state == DIRAC_PARSE_INFO_PREFIX) {
  66                 state                   = -1;
  67                 pc->is_synced           = 1;
  68                 pc->header_bytes_needed = 9;
  69                 pc->sync_offset         = i;
  70                 break;
  71             }
  72         }
  73     }
  74
  75     if (pc->is_synced) {
  76         pc->sync_offset = 0;
  77         for (; i < buf_size; i++) {
  78             if (state == DIRAC_PARSE_INFO_PREFIX) {
  79                 if ((buf_size - i) >= pc->header_bytes_needed) {
  80                     pc->state = -1;
  81                     return i + pc->header_bytes_needed;
  82                 } else {
  83                     pc->header_bytes_needed = 9 - (buf_size - i);
  84                     break;
  85                 }
  86             } else
  87                 state = (state << 8) | buf[i];
  88         }
  89     }
  90     pc->state = state;
  91     return -1;
  92 }
  93
  94 typedef struct DiracParseUnit {
  95     int next_pu_offset;
  96     int prev_pu_offset;
  97     uint8_t pu_type;
  98 } DiracParseUnit;
  99
 100 static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc,
 101                              int offset)
 102 {
 103     uint8_t *start = pc->buffer + offset;
 104     uint8_t *end   = pc->buffer + pc->index;
 105     if (start < pc->buffer || (start + 13 > end))
 106         return 0;
 107     pu->pu_type = start[4];
 108
 109     pu->next_pu_offset = AV_RB32(start + 5);
 110     pu->prev_pu_offset = AV_RB32(start + 9);
 111
 112     if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)
 113         pu->next_pu_offset = 13;
 114
 115     return 1;
 116 }
 117
 118 static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
 119                                int next, const uint8_t **buf, int *buf_size)
 120 {
 121     int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
 122                              s->dts == AV_NOPTS_VALUE);
 123     DiracParseContext *pc = s->priv_data;
 124
 125     if (pc->overread_index) {
 126         memcpy(pc->buffer, pc->buffer + pc->overread_index,
 127                pc->index - pc->overread_index);
 128         pc->index         -= pc->overread_index;
 129         pc->overread_index = 0;
 130         if (*buf_size == 0 && pc->buffer[4] == 0x10) {
 131             *buf      = pc->buffer;
 132             *buf_size = pc->index;
 133             return 0;
 134         }
 135     }
 136
 137     if (next == -1) {
 138         /* Found a possible frame start but not a frame end */
 139         void *new_buffer =
 140             av_fast_realloc(pc->buffer, &pc->buffer_size,
 141                             pc->index + (*buf_size - pc->sync_offset));
 142         pc->buffer = new_buffer;
 143         memcpy(pc->buffer + pc->index, (*buf + pc->sync_offset),
 144                *buf_size - pc->sync_offset);
 145         pc->index += *buf_size - pc->sync_offset;
 146         return -1;
 147     } else {
 148         /* Found a possible frame start and a  possible frame end */
 149         DiracParseUnit pu1, pu;
 150         void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
 151                                            pc->index + next);
 152         pc->buffer = new_buffer;
 153         memcpy(pc->buffer + pc->index, *buf, next);
 154         pc->index += next;
 155
 156         /* Need to check if we have a valid Parse Unit. We can't go by the
 157          * sync pattern 'BBCD' alone because arithmetic coding of the residual
 158          * and motion data can cause the pattern triggering a false start of
 159          * frame. So check if the previous parse offset of the next parse unit
 160          * is equal to the next parse offset of the current parse unit then
 161          * we can be pretty sure that we have a valid parse unit */
 162         if (!unpack_parse_unit(&pu1, pc, pc->index - 13)                     ||
 163             !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
 164             pu.next_pu_offset != pu1.prev_pu_offset) {
 165             pc->index              -= 9;
 166             *buf_size               = next - 9;
 167             pc->header_bytes_needed = 9;
 168             return -1;
 169         }
 170
 171         /* All non-frame data must be accompanied by frame data. This is to
 172          * ensure that pts is set correctly. So if the current parse unit is
 173          * not frame data, wait for frame data to come along */
 174
 175         pc->dirac_unit = pc->buffer + pc->index - 13 -
 176                          pu1.prev_pu_offset - pc->dirac_unit_size;
 177
 178         pc->dirac_unit_size += pu.next_pu_offset;
 179
 180         if ((pu.pu_type & 0x08) != 0x08) {
 181             pc->header_bytes_needed = 9;
 182             *buf_size               = next;
 183             return -1;
 184         }
 185
 186         /* Get the picture number to set the pts and dts*/
 187         if (parse_timing_info) {
 188             uint8_t *cur_pu = pc->buffer +
 189                               pc->index - 13 - pu1.prev_pu_offset;
 190             int pts = AV_RB32(cur_pu + 13);
 191             if (s->last_pts == 0 && s->last_dts == 0)
 192                 s->dts = pts - 1;
 193             else
 194                 s->dts = s->last_dts + 1;
 195             s->pts = pts;
 196             if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
 197                 avctx->has_b_frames = 1;
 198         }
 199         if (avctx->has_b_frames && s->pts == s->dts)
 200             s->pict_type = AV_PICTURE_TYPE_B;
 201
 202         /* Finally have a complete Dirac data unit */
 203         *buf      = pc->dirac_unit;
 204         *buf_size = pc->dirac_unit_size;
 205
 206         pc->dirac_unit_size     = 0;
 207         pc->overread_index      = pc->index - 13;
 208         pc->header_bytes_needed = 9;
 209     }
 210     return next;
 211 }
 212
 213 static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
 214                        const uint8_t **poutbuf, int *poutbuf_size,
 215                        const uint8_t *buf, int buf_size)
 216 {
 217     DiracParseContext *pc = s->priv_data;
 218     int next;
 219
 220     *poutbuf      = NULL;
 221     *poutbuf_size = 0;
 222
 223     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
 224         next          = buf_size;
 225         *poutbuf      = buf;
 226         *poutbuf_size = buf_size;
 227         /* Assume that data has been packetized into an encapsulation unit. */
 228     } else {
 229         next = find_frame_end(pc, buf, buf_size);
 230         if (!pc->is_synced && next == -1)
 231             /* No frame start found yet. So throw away the entire buffer. */
 232             return buf_size;
 233
 234         if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0)
 235             return buf_size;
 236     }
 237
 238     *poutbuf      = buf;
 239     *poutbuf_size = buf_size;
 240     return next;
 241 }
 242
 243 static void dirac_parse_close(AVCodecParserContext *s)
 244 {
 245     DiracParseContext *pc = s->priv_data;
 246
 247     if (pc->buffer_size > 0)
 248         av_free(pc->buffer);
 249 }
 250
 251 AVCodecParser ff_dirac_parser = {
 252     .codec_ids      = { AV_CODEC_ID_DIRAC },
 253     .priv_data_size = sizeof(DiracParseContext),
 254     .parser_parse   = dirac_parse,
 255     .parser_close   = dirac_parse_close,
 256 };