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libavcodec/dirac_parser.c

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00001 /*
00002  * Dirac parser
00003  *
00004  * Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org>
00005  * Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com>
00006  *
00007  * This file is part of FFmpeg.
00008  *
00009  * FFmpeg is free software; you can redistribute it and/or
00010  * modify it under the terms of the GNU Lesser General Public
00011  * License as published by the Free Software Foundation; either
00012  * version 2.1 of the License, or (at your option) any later version.
00013  *
00014  * FFmpeg is distributed in the hope that it will be useful,
00015  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00016  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00017  * Lesser General Public License for more details.
00018  *
00019  * You should have received a copy of the GNU Lesser General Public
00020  * License along with FFmpeg; if not, write to the Free Software
00021  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00022  */
00023 
00030 #include "libavutil/intreadwrite.h"
00031 #include "parser.h"
00032 
00033 #define DIRAC_PARSE_INFO_PREFIX 0x42424344
00034 
00039 typedef struct DiracParseContext {
00040     int state;
00041     int is_synced;
00042     int sync_offset;
00043     int header_bytes_needed;
00044     int overread_index;
00045     int buffer_size;
00046     int index;
00047     uint8_t *buffer;
00048     int dirac_unit_size;
00049     uint8_t *dirac_unit;
00050 } DiracParseContext;
00051 
00052 static int find_frame_end(DiracParseContext *pc,
00053                           const uint8_t *buf, int buf_size)
00054 {
00055     uint32_t state = pc->state;
00056     int i = 0;
00057 
00058     if (!pc->is_synced) {
00059         for (i = 0; i < buf_size; i++) {
00060             state = (state << 8) | buf[i];
00061             if (state == DIRAC_PARSE_INFO_PREFIX) {
00062                 state                   = -1;
00063                 pc->is_synced           = 1;
00064                 pc->header_bytes_needed = 9;
00065                 pc->sync_offset         = i;
00066                 break;
00067             }
00068         }
00069     }
00070 
00071     if (pc->is_synced) {
00072         pc->sync_offset = 0;
00073         for (; i < buf_size; i++) {
00074             if (state == DIRAC_PARSE_INFO_PREFIX) {
00075                 if ((buf_size-i) >= pc->header_bytes_needed) {
00076                     pc->state = -1;
00077                     return i + pc->header_bytes_needed;
00078                 } else {
00079                     pc->header_bytes_needed = 9-(buf_size-i);
00080                     break;
00081                 }
00082             } else
00083               state = (state << 8) | buf[i];
00084         }
00085     }
00086     pc->state = state;
00087     return -1;
00088 }
00089 
00090 typedef struct DiracParseUnit
00091 {
00092     int next_pu_offset;
00093     int prev_pu_offset;
00094     uint8_t pu_type;
00095 } DiracParseUnit;
00096 
00097 static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc,
00098                              int offset)
00099 {
00100     uint8_t *start = pc->buffer + offset;
00101     uint8_t *end   = pc->buffer + pc->index;
00102     if (start < pc->buffer || (start+13 > end))
00103         return 0;
00104     pu->pu_type = start[4];
00105 
00106     pu->next_pu_offset = AV_RB32(start+5);
00107     pu->prev_pu_offset = AV_RB32(start+9);
00108 
00109     if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)
00110         pu->next_pu_offset = 13;
00111 
00112     return 1;
00113 }
00114 
00115 static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
00116                                int next, const uint8_t **buf, int *buf_size)
00117 {
00118     int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
00119                              s->dts == AV_NOPTS_VALUE);
00120     DiracParseContext *pc = s->priv_data;
00121 
00122     if (pc->overread_index) {
00123         memcpy(pc->buffer, pc->buffer + pc->overread_index,
00124                pc->index - pc->overread_index);
00125         pc->index -= pc->overread_index;
00126         pc->overread_index = 0;
00127         if (*buf_size == 0 && pc->buffer[4] == 0x10) {
00128             *buf      = pc->buffer;
00129             *buf_size = pc->index;
00130             return 0;
00131         }
00132     }
00133 
00134     if ( next == -1) {
00135         /* Found a possible frame start but not a frame end */
00136         void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
00137                                            pc->index + (*buf_size -
00138                                                         pc->sync_offset));
00139         pc->buffer = new_buffer;
00140         memcpy(pc->buffer+pc->index, (*buf + pc->sync_offset),
00141                *buf_size - pc->sync_offset);
00142         pc->index += *buf_size - pc->sync_offset;
00143         return -1;
00144     } else {
00145         /* Found a possible frame start and a  possible frame end */
00146         DiracParseUnit pu1, pu;
00147         void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
00148                                            pc->index + next);
00149         pc->buffer = new_buffer;
00150         memcpy(pc->buffer + pc->index, *buf, next);
00151         pc->index += next;
00152 
00153         /* Need to check if we have a valid Parse Unit. We can't go by the
00154          * sync pattern 'BBCD' alone because arithmetic coding of the residual
00155          * and motion data can cause the pattern triggering a false start of
00156          * frame. So check if the previous parse offset of the next parse unit
00157          * is equal to the next parse offset of the current parse unit then
00158          * we can be pretty sure that we have a valid parse unit */
00159         if (!unpack_parse_unit(&pu1, pc, pc->index - 13)                     ||
00160             !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
00161             pu.next_pu_offset != pu1.prev_pu_offset) {
00162             pc->index -= 9;
00163             *buf_size = next-9;
00164             pc->header_bytes_needed = 9;
00165             return -1;
00166         }
00167 
00168         /* All non-frame data must be accompanied by frame data. This is to
00169          * ensure that pts is set correctly. So if the current parse unit is
00170          * not frame data, wait for frame data to come along */
00171 
00172         pc->dirac_unit = pc->buffer + pc->index - 13 -
00173                          pu1.prev_pu_offset - pc->dirac_unit_size;
00174 
00175         pc->dirac_unit_size += pu.next_pu_offset;
00176 
00177         if ((pu.pu_type&0x08) != 0x08) {
00178             pc->header_bytes_needed = 9;
00179             *buf_size = next;
00180             return -1;
00181         }
00182 
00183         /* Get the picture number to set the pts and dts*/
00184         if (parse_timing_info) {
00185             uint8_t *cur_pu = pc->buffer +
00186                               pc->index - 13 - pu1.prev_pu_offset;
00187             int pts =  AV_RB32(cur_pu + 13);
00188             if (s->last_pts == 0 && s->last_dts == 0)
00189                 s->dts = pts - 1;
00190             else
00191                 s->dts = s->last_dts+1;
00192             s->pts = pts;
00193             if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
00194                 avctx->has_b_frames = 1;
00195         }
00196         if (avctx->has_b_frames && s->pts == s->dts)
00197              s->pict_type = FF_B_TYPE;
00198 
00199         /* Finally have a complete Dirac data unit */
00200         *buf      = pc->dirac_unit;
00201         *buf_size = pc->dirac_unit_size;
00202 
00203         pc->dirac_unit_size     = 0;
00204         pc->overread_index      = pc->index-13;
00205         pc->header_bytes_needed = 9;
00206     }
00207     return next;
00208 }
00209 
00210 static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
00211                        const uint8_t **poutbuf, int *poutbuf_size,
00212                        const uint8_t *buf, int buf_size)
00213 {
00214     DiracParseContext *pc = s->priv_data;
00215     int next;
00216 
00217     *poutbuf = NULL;
00218     *poutbuf_size = 0;
00219 
00220     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
00221         next = buf_size;
00222         *poutbuf = buf;
00223         *poutbuf_size = buf_size;
00224         /* Assume that data has been packetized into an encapsulation unit. */
00225     } else {
00226         next = find_frame_end(pc, buf, buf_size);
00227         if (!pc->is_synced && next == -1) {
00228             /* No frame start found yet. So throw away the entire buffer. */
00229             return buf_size;
00230         }
00231 
00232         if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0) {
00233             return buf_size;
00234         }
00235     }
00236 
00237     *poutbuf = buf;
00238     *poutbuf_size = buf_size;
00239     return next;
00240 }
00241 
00242 static void dirac_parse_close(AVCodecParserContext *s)
00243 {
00244     DiracParseContext *pc = s->priv_data;
00245 
00246     if (pc->buffer_size > 0)
00247         av_free(pc->buffer);
00248 }
00249 
00250 AVCodecParser dirac_parser = {
00251     { CODEC_ID_DIRAC },
00252     sizeof(DiracParseContext),
00253     NULL,
00254     dirac_parse,
00255     dirac_parse_close,
00256 };

Generated on Fri Sep 16 2011 17:17:35 for FFmpeg by  doxygen 1.7.1