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 FFmpeg.
   8  *
   9  * FFmpeg 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  * FFmpeg 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 FFmpeg; 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 libavcodec/dirac_parser.c
  26  * Dirac Parser
  27  * @author Marco Gerards <marco@gnu.org>
  28  */
  29
  30 #include "libavutil/intreadwrite.h"
  31 #include "parser.h"
  32
  33 #define DIRAC_PARSE_INFO_PREFIX 0x42424344
  34
  35 /**
  36  * Finds the end of the current frame in the bitstream.
  37  * @return the position of the first byte of the next frame or -1
  38  */
  39 typedef struct DiracParseContext {
  40     int state;
  41     int is_synced;
  42     int sync_offset;
  43     int header_bytes_needed;
  44     int overread_index;
  45     int buffer_size;
  46     int index;
  47     uint8_t *buffer;
  48     int dirac_unit_size;
  49     uint8_t *dirac_unit;
  50 } DiracParseContext;
  51
  52 static int find_frame_end(DiracParseContext *pc,
  53                           const uint8_t *buf, int buf_size)
  54 {
  55     uint32_t state = pc->state;
  56     int i = 0;
  57
  58     if (!pc->is_synced) {
  59         for (i = 0; i < buf_size; i++) {
  60             state = (state << 8) | buf[i];
  61             if (state == DIRAC_PARSE_INFO_PREFIX) {
  62                 state                   = -1;
  63                 pc->is_synced           = 1;
  64                 pc->header_bytes_needed = 9;
  65                 pc->sync_offset         = i;
  66                 break;
  67             }
  68         }
  69     }
  70
  71     if (pc->is_synced) {
  72         pc->sync_offset = 0;
  73         for (; i < buf_size; i++) {
  74             if (state == DIRAC_PARSE_INFO_PREFIX) {
  75                 if ((buf_size-i) >= pc->header_bytes_needed) {
  76                     pc->state = -1;
  77                     return i + pc->header_bytes_needed;
  78                 } else {
  79                     pc->header_bytes_needed = 9-(buf_size-i);
  80                     break;
  81                 }
  82             } else
  83               state = (state << 8) | buf[i];
  84         }
  85     }
  86     pc->state = state;
  87     return -1;
  88 }
  89
  90 typedef struct DiracParseUnit
  91 {
  92     int next_pu_offset;
  93     int prev_pu_offset;
  94     uint8_t pu_type;
  95 } DiracParseUnit;
  96
  97 static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc,
  98                              int offset)
  99 {
 100     uint8_t *start = pc->buffer + offset;
 101     uint8_t *end   = pc->buffer + pc->index;
 102     if (start < pc->buffer || (start+13 > end))
 103         return 0;
 104     pu->pu_type = start[4];
 105
 106     pu->next_pu_offset = AV_RB32(start+5);
 107     pu->prev_pu_offset = AV_RB32(start+9);
 108
 109     if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)
 110         pu->next_pu_offset = 13;
 111
 112     return 1;
 113 }
 114
 115 static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
 116                                int next, const uint8_t **buf, int *buf_size)
 117 {
 118     int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
 119                              s->dts == AV_NOPTS_VALUE);
 120     DiracParseContext *pc = s->priv_data;
 121
 122     if (pc->overread_index) {
 123         memcpy(pc->buffer, pc->buffer + pc->overread_index,
 124                pc->index - pc->overread_index);
 125         pc->index -= pc->overread_index;
 126         pc->overread_index = 0;
 127         if (*buf_size == 0 && pc->buffer[4] == 0x10) {
 128             *buf      = pc->buffer;
 129             *buf_size = pc->index;
 130             return 0;
 131         }
 132     }
 133
 134     if ( next == -1) {
 135         /* Found a possible frame start but not a frame end */
 136         void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
 137                                            pc->index + (*buf_size -
 138                                                         pc->sync_offset));
 139         pc->buffer = new_buffer;
 140         memcpy(pc->buffer+pc->index, (*buf + pc->sync_offset),
 141                *buf_size - pc->sync_offset);
 142         pc->index += *buf_size - pc->sync_offset;
 143         return -1;
 144     } else {
 145         /* Found a possible frame start and a  possible frame end */
 146         DiracParseUnit pu1, pu;
 147         void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
 148                                            pc->index + next);
 149         pc->buffer = new_buffer;
 150         memcpy(pc->buffer + pc->index, *buf, next);
 151         pc->index += next;
 152
 153         /* Need to check if we have a valid Parse Unit. We can't go by the
 154          * sync pattern 'BBCD' alone because arithmetic coding of the residual
 155          * and motion data can cause the pattern triggering a false start of
 156          * frame. So check if the previous parse offset of the next parse unit
 157          * is equal to the next parse offset of the current parse unit then
 158          * we can be pretty sure that we have a valid parse unit */
 159         if (!unpack_parse_unit(&pu1, pc, pc->index - 13)                     ||
 160             !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
 161             pu.next_pu_offset != pu1.prev_pu_offset) {
 162             pc->index -= 9;
 163             *buf_size = next-9;
 164             pc->header_bytes_needed = 9;
 165             return -1;
 166         }
 167
 168         /* All non-frame data must be accompanied by frame data. This is to
 169          * ensure that pts is set correctly. So if the current parse unit is
 170          * not frame data, wait for frame data to come along */
 171
 172         pc->dirac_unit = pc->buffer + pc->index - 13 -
 173                          pu1.prev_pu_offset - pc->dirac_unit_size;
 174
 175         pc->dirac_unit_size += pu.next_pu_offset;
 176
 177         if ((pu.pu_type&0x08) != 0x08) {
 178             pc->header_bytes_needed = 9;
 179             *buf_size = next;
 180             return -1;
 181         }
 182
 183         /* Get the picture number to set the pts and dts*/
 184         if (parse_timing_info) {
 185             uint8_t *cur_pu = pc->buffer +
 186                               pc->index - 13 - pu1.prev_pu_offset;
 187             int pts =  AV_RB32(cur_pu + 13);
 188             if (s->last_pts == 0 && s->last_dts == 0)
 189                 s->dts = pts - 1;
 190             else
 191                 s->dts = s->last_dts+1;
 192             s->pts = pts;
 193             if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
 194                 avctx->has_b_frames = 1;
 195         }
 196         if (avctx->has_b_frames && s->pts == s->dts)
 197              s->pict_type = FF_B_TYPE;
 198
 199         /* Finally have a complete Dirac data unit */
 200         *buf      = pc->dirac_unit;
 201         *buf_size = pc->dirac_unit_size;
 202
 203         pc->dirac_unit_size     = 0;
 204         pc->overread_index      = pc->index-13;
 205         pc->header_bytes_needed = 9;
 206     }
 207     return next;
 208 }
 209
 210 static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
 211                        const uint8_t **poutbuf, int *poutbuf_size,
 212                        const uint8_t *buf, int buf_size)
 213 {
 214     DiracParseContext *pc = s->priv_data;
 215     int next;
 216
 217     *poutbuf = NULL;
 218     *poutbuf_size = 0;
 219
 220     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
 221         next = buf_size;
 222         *poutbuf = buf;
 223         *poutbuf_size = buf_size;
 224         /* Assume that data has been packetized into an encapsulation unit. */
 225     } else {
 226         next = find_frame_end(pc, buf, buf_size);
 227         if (!pc->is_synced && next == -1) {
 228             /* No frame start found yet. So throw away the entire buffer. */
 229             return buf_size;
 230         }
 231
 232         if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0) {
 233             return buf_size;
 234         }
 235     }
 236
 237     *poutbuf = buf;
 238     *poutbuf_size = buf_size;
 239     return next;
 240 }
 241
 242 static void dirac_parse_close(AVCodecParserContext *s)
 243 {
 244     DiracParseContext *pc = s->priv_data;
 245
 246     if (pc->buffer_size > 0)
 247         av_free(pc->buffer);
 248 }
 249
 250 AVCodecParser dirac_parser = {
 251     { CODEC_ID_DIRAC },
 252     sizeof(DiracParseContext),
 253     NULL,
 254     dirac_parse,
 255     dirac_parse_close,
 256 };