Libav 0.7.1
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00001 /* 00002 * FLAC parser 00003 * Copyright (c) 2010 Michael Chinen 00004 * 00005 * This file is part of Libav. 00006 * 00007 * Libav is free software; you can redistribute it and/or 00008 * modify it under the terms of the GNU Lesser General Public 00009 * License as published by the Free Software Foundation; either 00010 * version 2.1 of the License, or (at your option) any later version. 00011 * 00012 * Libav is distributed in the hope that it will be useful, 00013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00015 * Lesser General Public License for more details. 00016 * 00017 * You should have received a copy of the GNU Lesser General Public 00018 * License along with Libav; if not, write to the Free Software 00019 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00020 */ 00021 00035 #include "libavutil/crc.h" 00036 #include "libavutil/fifo.h" 00037 #include "bytestream.h" 00038 #include "parser.h" 00039 #include "flac.h" 00040 00042 #define FLAC_MAX_SEQUENTIAL_HEADERS 3 00043 00044 #define FLAC_MIN_HEADERS 10 00045 00046 #define FLAC_AVG_FRAME_SIZE 8192 00047 00049 #define FLAC_HEADER_BASE_SCORE 10 00050 #define FLAC_HEADER_CHANGED_PENALTY 7 00051 #define FLAC_HEADER_CRC_FAIL_PENALTY 50 00052 #define FLAC_HEADER_NOT_PENALIZED_YET 100000 00053 #define FLAC_HEADER_NOT_SCORED_YET -100000 00054 00056 #define MAX_FRAME_HEADER_SIZE 16 00057 00058 typedef struct FLACHeaderMarker { 00059 int offset; 00060 int *link_penalty; 00062 int max_score; 00064 FLACFrameInfo fi; 00065 struct FLACHeaderMarker *next; 00068 struct FLACHeaderMarker *best_child; 00071 } FLACHeaderMarker; 00072 00073 typedef struct FLACParseContext { 00074 AVCodecContext *avctx; 00075 FLACHeaderMarker *headers; 00077 FLACHeaderMarker *best_header; 00078 int nb_headers_found; 00080 int nb_headers_buffered; 00081 int best_header_valid; 00083 AVFifoBuffer *fifo_buf; 00085 int end_padded; 00086 uint8_t *wrap_buf; 00087 int wrap_buf_allocated_size; 00088 } FLACParseContext; 00089 00090 static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf, 00091 FLACFrameInfo *fi) 00092 { 00093 GetBitContext gb; 00094 init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8); 00095 return !ff_flac_decode_frame_header(avctx, &gb, fi, 127); 00096 } 00097 00111 static uint8_t* flac_fifo_read_wrap(FLACParseContext *fpc, int offset, int len, 00112 uint8_t** wrap_buf, int* allocated_size) 00113 { 00114 AVFifoBuffer *f = fpc->fifo_buf; 00115 uint8_t *start = f->rptr + offset; 00116 uint8_t *tmp_buf; 00117 00118 if (start >= f->end) 00119 start -= f->end - f->buffer; 00120 if (f->end - start >= len) 00121 return start; 00122 00123 tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len); 00124 00125 if (!tmp_buf) { 00126 av_log(fpc->avctx, AV_LOG_ERROR, 00127 "couldn't reallocate wrap buffer of size %d", len); 00128 return NULL; 00129 } 00130 *wrap_buf = tmp_buf; 00131 do { 00132 int seg_len = FFMIN(f->end - start, len); 00133 memcpy(tmp_buf, start, seg_len); 00134 tmp_buf = (uint8_t*)tmp_buf + seg_len; 00135 // memory barrier needed for SMP here in theory 00136 00137 start += seg_len - (f->end - f->buffer); 00138 len -= seg_len; 00139 } while (len > 0); 00140 00141 return *wrap_buf; 00142 } 00143 00151 static uint8_t* flac_fifo_read(FLACParseContext *fpc, int offset, int *len) 00152 { 00153 AVFifoBuffer *f = fpc->fifo_buf; 00154 uint8_t *start = f->rptr + offset; 00155 00156 if (start >= f->end) 00157 start -= f->end - f->buffer; 00158 *len = FFMIN(*len, f->end - start); 00159 return start; 00160 } 00161 00162 static int find_headers_search_validate(FLACParseContext *fpc, int offset) 00163 { 00164 FLACFrameInfo fi; 00165 uint8_t *header_buf; 00166 int size = 0; 00167 header_buf = flac_fifo_read_wrap(fpc, offset, 00168 MAX_FRAME_HEADER_SIZE, 00169 &fpc->wrap_buf, 00170 &fpc->wrap_buf_allocated_size); 00171 if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) { 00172 FLACHeaderMarker **end_handle = &fpc->headers; 00173 int i; 00174 00175 size = 0; 00176 while (*end_handle) { 00177 end_handle = &(*end_handle)->next; 00178 size++; 00179 } 00180 00181 *end_handle = av_mallocz(sizeof(FLACHeaderMarker)); 00182 if (!*end_handle) { 00183 av_log(fpc->avctx, AV_LOG_ERROR, 00184 "couldn't allocate FLACHeaderMarker\n"); 00185 return AVERROR(ENOMEM); 00186 } 00187 (*end_handle)->fi = fi; 00188 (*end_handle)->offset = offset; 00189 (*end_handle)->link_penalty = av_malloc(sizeof(int) * 00190 FLAC_MAX_SEQUENTIAL_HEADERS); 00191 for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) 00192 (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET; 00193 00194 fpc->nb_headers_found++; 00195 size++; 00196 } 00197 return size; 00198 } 00199 00200 static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size, 00201 int search_start) 00202 00203 { 00204 int size = 0, mod_offset = (buf_size - 1) % 4, i, j; 00205 uint32_t x; 00206 00207 for (i = 0; i < mod_offset; i++) { 00208 if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8) 00209 size = find_headers_search_validate(fpc, search_start + i); 00210 } 00211 00212 for (; i < buf_size - 1; i += 4) { 00213 x = AV_RB32(buf + i); 00214 if (((x & ~(x + 0x01010101)) & 0x80808080)) { 00215 for (j = 0; j < 4; j++) { 00216 if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8) 00217 size = find_headers_search_validate(fpc, search_start + i + j); 00218 } 00219 } 00220 } 00221 return size; 00222 } 00223 00224 static int find_new_headers(FLACParseContext *fpc, int search_start) 00225 { 00226 FLACHeaderMarker *end; 00227 int search_end, size = 0, read_len, temp; 00228 uint8_t *buf; 00229 fpc->nb_headers_found = 0; 00230 00231 /* Search for a new header of at most 16 bytes. */ 00232 search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1); 00233 read_len = search_end - search_start + 1; 00234 buf = flac_fifo_read(fpc, search_start, &read_len); 00235 size = find_headers_search(fpc, buf, read_len, search_start); 00236 search_start += read_len - 1; 00237 00238 /* If fifo end was hit do the wrap around. */ 00239 if (search_start != search_end) { 00240 uint8_t wrap[2]; 00241 00242 wrap[0] = buf[read_len - 1]; 00243 read_len = search_end - search_start + 1; 00244 00245 /* search_start + 1 is the post-wrap offset in the fifo. */ 00246 buf = flac_fifo_read(fpc, search_start + 1, &read_len); 00247 wrap[1] = buf[0]; 00248 00249 if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) { 00250 temp = find_headers_search_validate(fpc, search_start); 00251 size = FFMAX(size, temp); 00252 } 00253 search_start++; 00254 00255 /* Continue to do the last half of the wrap. */ 00256 temp = find_headers_search(fpc, buf, read_len, search_start); 00257 size = FFMAX(size, temp); 00258 search_start += read_len - 1; 00259 } 00260 00261 /* Return the size even if no new headers were found. */ 00262 if (!size && fpc->headers) 00263 for (end = fpc->headers; end; end = end->next) 00264 size++; 00265 return size; 00266 } 00267 00268 static int check_header_mismatch(FLACParseContext *fpc, 00269 FLACHeaderMarker *header, 00270 FLACHeaderMarker *child, 00271 int log_level_offset) 00272 { 00273 FLACFrameInfo *header_fi = &header->fi, *child_fi = &child->fi; 00274 int deduction = 0, deduction_expected = 0, i; 00275 if (child_fi->samplerate != header_fi->samplerate) { 00276 deduction += FLAC_HEADER_CHANGED_PENALTY; 00277 av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset, 00278 "sample rate change detected in adjacent frames\n"); 00279 } 00280 if (child_fi->bps != header_fi->bps) { 00281 deduction += FLAC_HEADER_CHANGED_PENALTY; 00282 av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset, 00283 "bits per sample change detected in adjacent frames\n"); 00284 } 00285 if (child_fi->is_var_size != header_fi->is_var_size) { 00286 /* Changing blocking strategy not allowed per the spec */ 00287 deduction += FLAC_HEADER_BASE_SCORE; 00288 av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset, 00289 "blocking strategy change detected in adjacent frames\n"); 00290 } 00291 if (child_fi->channels != header_fi->channels) { 00292 deduction += FLAC_HEADER_CHANGED_PENALTY; 00293 av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset, 00294 "number of channels change detected in adjacent frames\n"); 00295 } 00296 /* Check sample and frame numbers. */ 00297 if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num 00298 != header_fi->blocksize) && 00299 (child_fi->frame_or_sample_num 00300 != header_fi->frame_or_sample_num + 1)) { 00301 FLACHeaderMarker *curr; 00302 int expected_frame_num, expected_sample_num; 00303 /* If there are frames in the middle we expect this deduction, 00304 as they are probably valid and this one follows it */ 00305 00306 expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num; 00307 curr = header; 00308 while (curr != child) { 00309 /* Ignore frames that failed all crc checks */ 00310 for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) { 00311 if (curr->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY) { 00312 expected_frame_num++; 00313 expected_sample_num += curr->fi.blocksize; 00314 break; 00315 } 00316 } 00317 curr = curr->next; 00318 } 00319 00320 if (expected_frame_num == child_fi->frame_or_sample_num || 00321 expected_sample_num == child_fi->frame_or_sample_num) 00322 deduction_expected = deduction ? 0 : 1; 00323 00324 deduction += FLAC_HEADER_CHANGED_PENALTY; 00325 av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset, 00326 "sample/frame number mismatch in adjacent frames\n"); 00327 } 00328 00329 /* If we have suspicious headers, check the CRC between them */ 00330 if (deduction && !deduction_expected) { 00331 FLACHeaderMarker *curr; 00332 int read_len; 00333 uint8_t *buf; 00334 uint32_t crc = 1; 00335 int inverted_test = 0; 00336 00337 /* Since CRC is expensive only do it if we haven't yet. 00338 This assumes a CRC penalty is greater than all other check penalties */ 00339 curr = header->next; 00340 for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++) 00341 curr = curr->next; 00342 00343 if (header->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY || 00344 header->link_penalty[i] == FLAC_HEADER_NOT_PENALIZED_YET) { 00345 FLACHeaderMarker *start, *end; 00346 00347 /* Although overlapping chains are scored, the crc should never 00348 have to be computed twice for a single byte. */ 00349 start = header; 00350 end = child; 00351 if (i > 0 && 00352 header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) { 00353 while (start->next != child) 00354 start = start->next; 00355 inverted_test = 1; 00356 } else if (i > 0 && 00357 header->next->link_penalty[i-1] >= 00358 FLAC_HEADER_CRC_FAIL_PENALTY ) { 00359 end = header->next; 00360 inverted_test = 1; 00361 } 00362 00363 read_len = end->offset - start->offset; 00364 buf = flac_fifo_read(fpc, start->offset, &read_len); 00365 crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len); 00366 read_len = (end->offset - start->offset) - read_len; 00367 00368 if (read_len) { 00369 buf = flac_fifo_read(fpc, end->offset - read_len, &read_len); 00370 crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len); 00371 } 00372 } 00373 00374 if (!crc ^ !inverted_test) { 00375 deduction += FLAC_HEADER_CRC_FAIL_PENALTY; 00376 av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset, 00377 "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n", 00378 header->offset, header_fi->frame_or_sample_num, 00379 child->offset, child_fi->frame_or_sample_num); 00380 } 00381 } 00382 return deduction; 00383 } 00384 00395 static int score_header(FLACParseContext *fpc, FLACHeaderMarker *header) 00396 { 00397 FLACHeaderMarker *child; 00398 int dist = 0; 00399 int child_score; 00400 00401 if (header->max_score != FLAC_HEADER_NOT_SCORED_YET) 00402 return header->max_score; 00403 00404 header->max_score = FLAC_HEADER_BASE_SCORE; 00405 00406 /* Check and compute the children's scores. */ 00407 child = header->next; 00408 for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) { 00409 /* Look at the child's frame header info and penalize suspicious 00410 changes between the headers. */ 00411 if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) { 00412 header->link_penalty[dist] = check_header_mismatch(fpc, header, 00413 child, AV_LOG_DEBUG); 00414 } 00415 child_score = score_header(fpc, child) - header->link_penalty[dist]; 00416 00417 if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) { 00418 /* Keep the child because the frame scoring is dynamic. */ 00419 header->best_child = child; 00420 header->max_score = FLAC_HEADER_BASE_SCORE + child_score; 00421 } 00422 child = child->next; 00423 } 00424 00425 return header->max_score; 00426 } 00427 00428 static void score_sequences(FLACParseContext *fpc) 00429 { 00430 FLACHeaderMarker *curr; 00431 int best_score = FLAC_HEADER_NOT_SCORED_YET; 00432 /* First pass to clear all old scores. */ 00433 for (curr = fpc->headers; curr; curr = curr->next) 00434 curr->max_score = FLAC_HEADER_NOT_SCORED_YET; 00435 00436 /* Do a second pass to score them all. */ 00437 for (curr = fpc->headers; curr; curr = curr->next) { 00438 if (score_header(fpc, curr) > best_score) { 00439 fpc->best_header = curr; 00440 best_score = curr->max_score; 00441 } 00442 } 00443 } 00444 00445 static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf, 00446 int *poutbuf_size) 00447 { 00448 FLACHeaderMarker *header = fpc->best_header; 00449 FLACHeaderMarker *child = header->best_child; 00450 if (!child) { 00451 *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset; 00452 } else { 00453 *poutbuf_size = child->offset - header->offset; 00454 00455 /* If the child has suspicious changes, log them */ 00456 check_header_mismatch(fpc, header, child, 0); 00457 } 00458 00459 fpc->avctx->sample_rate = header->fi.samplerate; 00460 fpc->avctx->channels = header->fi.channels; 00461 fpc->avctx->frame_size = header->fi.blocksize; 00462 *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size, 00463 &fpc->wrap_buf, 00464 &fpc->wrap_buf_allocated_size); 00465 00466 fpc->best_header_valid = 0; 00467 /* Return the negative overread index so the client can compute pos. 00468 This should be the amount overread to the beginning of the child */ 00469 if (child) 00470 return child->offset - av_fifo_size(fpc->fifo_buf); 00471 return 0; 00472 } 00473 00474 static int flac_parse(AVCodecParserContext *s, AVCodecContext *avctx, 00475 const uint8_t **poutbuf, int *poutbuf_size, 00476 const uint8_t *buf, int buf_size) 00477 { 00478 FLACParseContext *fpc = s->priv_data; 00479 FLACHeaderMarker *curr; 00480 int nb_headers; 00481 const uint8_t *read_end = buf; 00482 const uint8_t *read_start = buf; 00483 00484 if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) { 00485 FLACFrameInfo fi; 00486 if (frame_header_is_valid(avctx, buf, &fi)) 00487 avctx->frame_size = fi.blocksize; 00488 *poutbuf = buf; 00489 *poutbuf_size = buf_size; 00490 return buf_size; 00491 } 00492 00493 fpc->avctx = avctx; 00494 if (fpc->best_header_valid) 00495 return get_best_header(fpc, poutbuf, poutbuf_size); 00496 00497 /* If a best_header was found last call remove it with the buffer data. */ 00498 if (fpc->best_header && fpc->best_header->best_child) { 00499 FLACHeaderMarker *temp; 00500 FLACHeaderMarker *best_child = fpc->best_header->best_child; 00501 00502 /* Remove headers in list until the end of the best_header. */ 00503 for (curr = fpc->headers; curr != best_child; curr = temp) { 00504 if (curr != fpc->best_header) { 00505 av_log(avctx, AV_LOG_DEBUG, 00506 "dropping low score %i frame header from offset %i to %i\n", 00507 curr->max_score, curr->offset, curr->next->offset); 00508 } 00509 temp = curr->next; 00510 av_freep(&curr->link_penalty); 00511 av_free(curr); 00512 fpc->nb_headers_buffered--; 00513 } 00514 /* Release returned data from ring buffer. */ 00515 av_fifo_drain(fpc->fifo_buf, best_child->offset); 00516 00517 /* Fix the offset for the headers remaining to match the new buffer. */ 00518 for (curr = best_child->next; curr; curr = curr->next) 00519 curr->offset -= best_child->offset; 00520 00521 fpc->nb_headers_buffered--; 00522 best_child->offset = 0; 00523 fpc->headers = best_child; 00524 if (fpc->nb_headers_buffered >= FLAC_MIN_HEADERS) { 00525 fpc->best_header = best_child; 00526 return get_best_header(fpc, poutbuf, poutbuf_size); 00527 } 00528 fpc->best_header = NULL; 00529 } else if (fpc->best_header) { 00530 /* No end frame no need to delete the buffer; probably eof */ 00531 FLACHeaderMarker *temp; 00532 00533 for (curr = fpc->headers; curr != fpc->best_header; curr = temp) { 00534 temp = curr->next; 00535 av_freep(&curr->link_penalty); 00536 av_free(curr); 00537 } 00538 fpc->headers = fpc->best_header->next; 00539 av_freep(&fpc->best_header->link_penalty); 00540 av_freep(&fpc->best_header); 00541 } 00542 00543 /* Find and score new headers. */ 00544 while ((buf && read_end < buf + buf_size && 00545 fpc->nb_headers_buffered < FLAC_MIN_HEADERS) 00546 || (!buf && !fpc->end_padded)) { 00547 int start_offset; 00548 00549 /* Pad the end once if EOF, to check the final region for headers. */ 00550 if (!buf) { 00551 fpc->end_padded = 1; 00552 buf_size = MAX_FRAME_HEADER_SIZE; 00553 read_end = read_start + MAX_FRAME_HEADER_SIZE; 00554 } else { 00555 /* The maximum read size is the upper-bound of what the parser 00556 needs to have the required number of frames buffered */ 00557 int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1; 00558 read_end = read_end + FFMIN(buf + buf_size - read_end, 00559 nb_desired * FLAC_AVG_FRAME_SIZE); 00560 } 00561 00562 /* Fill the buffer. */ 00563 if (av_fifo_realloc2(fpc->fifo_buf, 00564 (read_end - read_start) + av_fifo_size(fpc->fifo_buf)) < 0) { 00565 av_log(avctx, AV_LOG_ERROR, 00566 "couldn't reallocate buffer of size %td\n", 00567 (read_end - read_start) + av_fifo_size(fpc->fifo_buf)); 00568 goto handle_error; 00569 } 00570 00571 if (buf) { 00572 av_fifo_generic_write(fpc->fifo_buf, (void*) read_start, 00573 read_end - read_start, NULL); 00574 } else { 00575 int8_t pad[MAX_FRAME_HEADER_SIZE]; 00576 memset(pad, 0, sizeof(pad)); 00577 av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL); 00578 } 00579 00580 /* Tag headers and update sequences. */ 00581 start_offset = av_fifo_size(fpc->fifo_buf) - 00582 ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1)); 00583 start_offset = FFMAX(0, start_offset); 00584 nb_headers = find_new_headers(fpc, start_offset); 00585 00586 if (nb_headers < 0) { 00587 av_log(avctx, AV_LOG_ERROR, 00588 "find_new_headers couldn't allocate FLAC header\n"); 00589 goto handle_error; 00590 } 00591 00592 fpc->nb_headers_buffered = nb_headers; 00593 /* Wait till FLAC_MIN_HEADERS to output a valid frame. */ 00594 if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) { 00595 if (buf && read_end < buf + buf_size) { 00596 read_start = read_end; 00597 continue; 00598 } else { 00599 goto handle_error; 00600 } 00601 } 00602 00603 /* If headers found, update the scores since we have longer chains. */ 00604 if (fpc->end_padded || fpc->nb_headers_found) 00605 score_sequences(fpc); 00606 00607 /* restore the state pre-padding */ 00608 if (fpc->end_padded) { 00609 /* HACK: drain the tail of the fifo */ 00610 fpc->fifo_buf->wptr -= MAX_FRAME_HEADER_SIZE; 00611 fpc->fifo_buf->wndx -= MAX_FRAME_HEADER_SIZE; 00612 if (fpc->fifo_buf->wptr < 0) { 00613 fpc->fifo_buf->wptr += fpc->fifo_buf->end - 00614 fpc->fifo_buf->buffer; 00615 } 00616 buf_size = 0; 00617 read_start = read_end = NULL; 00618 } 00619 } 00620 00621 curr = fpc->headers; 00622 for (curr = fpc->headers; curr; curr = curr->next) 00623 if (!fpc->best_header || curr->max_score > fpc->best_header->max_score) 00624 fpc->best_header = curr; 00625 00626 if (fpc->best_header) { 00627 fpc->best_header_valid = 1; 00628 if (fpc->best_header->offset > 0) { 00629 /* Output a junk frame. */ 00630 av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n", 00631 fpc->best_header->offset); 00632 00633 /* Set frame_size to 0. It is unknown or invalid in a junk frame. */ 00634 avctx->frame_size = 0; 00635 *poutbuf_size = fpc->best_header->offset; 00636 *poutbuf = flac_fifo_read_wrap(fpc, 0, *poutbuf_size, 00637 &fpc->wrap_buf, 00638 &fpc->wrap_buf_allocated_size); 00639 return buf_size ? (read_end - buf) : (fpc->best_header->offset - 00640 av_fifo_size(fpc->fifo_buf)); 00641 } 00642 if (!buf_size) 00643 return get_best_header(fpc, poutbuf, poutbuf_size); 00644 } 00645 00646 handle_error: 00647 *poutbuf = NULL; 00648 *poutbuf_size = 0; 00649 return read_end - buf; 00650 } 00651 00652 static int flac_parse_init(AVCodecParserContext *c) 00653 { 00654 FLACParseContext *fpc = c->priv_data; 00655 /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before 00656 it drains. This is allocated early to avoid slow reallocation. */ 00657 fpc->fifo_buf = av_fifo_alloc(FLAC_AVG_FRAME_SIZE * (FLAC_MIN_HEADERS + 3)); 00658 return 0; 00659 } 00660 00661 static void flac_parse_close(AVCodecParserContext *c) 00662 { 00663 FLACParseContext *fpc = c->priv_data; 00664 FLACHeaderMarker *curr = fpc->headers, *temp; 00665 00666 while (curr) { 00667 temp = curr->next; 00668 av_freep(&curr->link_penalty); 00669 av_free(curr); 00670 curr = temp; 00671 } 00672 av_fifo_free(fpc->fifo_buf); 00673 av_free(fpc->wrap_buf); 00674 } 00675 00676 AVCodecParser ff_flac_parser = { 00677 { CODEC_ID_FLAC }, 00678 sizeof(FLACParseContext), 00679 flac_parse_init, 00680 flac_parse, 00681 flac_parse_close, 00682 };