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 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 */ 39typedef 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 52static 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 90typedef struct DiracParseUnit 91{ 92 int next_pu_offset; 93 int prev_pu_offset; 94 uint8_t pu_type; 95} DiracParseUnit; 96 97static 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 115static 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 210static 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 242static 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 250AVCodecParser dirac_parser = { 251 { CODEC_ID_DIRAC }, 252 sizeof(DiracParseContext), 253 NULL, 254 dirac_parse, 255 dirac_parse_close, 256}; 257