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  1. /*
  2.  * FLAC parser
  3.  * Copyright (c) 2010 Michael Chinen
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. /**
  23.  * @file
  24.  * FLAC parser
  25.  *
  26.  * The FLAC parser buffers input until FLAC_MIN_HEADERS has been found.
  27.  * Each time it finds and verifies a CRC-8 header it sees which of the
  28.  * FLAC_MAX_SEQUENTIAL_HEADERS that came before it have a valid CRC-16 footer
  29.  * that ends at the newly found header.
  30.  * Headers are scored by FLAC_HEADER_BASE_SCORE plus the max of its crc-verified
  31.  * children, penalized by changes in sample rate, frame number, etc.
  32.  * The parser returns the frame with the highest score.
  33.  **/
  34.  
  35. #include "libavutil/attributes.h"
  36. #include "libavutil/crc.h"
  37. #include "libavutil/fifo.h"
  38. #include "bytestream.h"
  39. #include "parser.h"
  40. #include "flac.h"
  41.  
  42. /** maximum number of adjacent headers that compare CRCs against each other   */
  43. #define FLAC_MAX_SEQUENTIAL_HEADERS 3
  44. /** minimum number of headers buffered and checked before returning frames    */
  45. #define FLAC_MIN_HEADERS 10
  46. /** estimate for average size of a FLAC frame                                 */
  47. #define FLAC_AVG_FRAME_SIZE 8192
  48.  
  49. /** scoring settings for score_header */
  50. #define FLAC_HEADER_BASE_SCORE        10
  51. #define FLAC_HEADER_CHANGED_PENALTY   7
  52. #define FLAC_HEADER_CRC_FAIL_PENALTY  50
  53. #define FLAC_HEADER_NOT_PENALIZED_YET 100000
  54. #define FLAC_HEADER_NOT_SCORED_YET    -100000
  55.  
  56. /** largest possible size of flac header */
  57. #define MAX_FRAME_HEADER_SIZE 16
  58.  
  59. typedef struct FLACHeaderMarker {
  60.     int offset;       /**< byte offset from start of FLACParseContext->buffer */
  61.     int *link_penalty;  /**< pointer to array of local scores between this header
  62.                            and the one at a distance equal array position     */
  63.     int max_score;    /**< maximum score found after checking each child that
  64.                            has a valid CRC                                    */
  65.     FLACFrameInfo fi; /**< decoded frame header info                          */
  66.     struct FLACHeaderMarker *next;       /**< next CRC-8 verified header that
  67.                                               immediately follows this one in
  68.                                               the bytestream                  */
  69.     struct FLACHeaderMarker *best_child; /**< following frame header with
  70.                                               which this frame has the best
  71.                                               score with                      */
  72. } FLACHeaderMarker;
  73.  
  74. typedef struct FLACParseContext {
  75.     AVCodecParserContext *pc;      /**< parent context                        */
  76.     AVCodecContext *avctx;         /**< codec context pointer for logging     */
  77.     FLACHeaderMarker *headers;     /**< linked-list that starts at the first
  78.                                         CRC-8 verified header within buffer   */
  79.     FLACHeaderMarker *best_header; /**< highest scoring header within buffer  */
  80.     int nb_headers_found;          /**< number of headers found in the last
  81.                                         flac_parse() call                     */
  82.     int nb_headers_buffered;       /**< number of headers that are buffered   */
  83.     int best_header_valid;         /**< flag set when the parser returns junk;
  84.                                         if set return best_header next time   */
  85.     AVFifoBuffer *fifo_buf;        /**< buffer to store all data until headers
  86.                                         can be verified                       */
  87.     int end_padded;                /**< specifies if fifo_buf's end is padded */
  88.     uint8_t *wrap_buf;             /**< general fifo read buffer when wrapped */
  89.     int wrap_buf_allocated_size;   /**< actual allocated size of the buffer   */
  90.     FLACFrameInfo last_fi;         /**< last decoded frame header info        */
  91.     int last_fi_valid;             /**< set if last_fi is valid               */
  92. } FLACParseContext;
  93.  
  94. static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
  95.                                  FLACFrameInfo *fi)
  96. {
  97.     GetBitContext gb;
  98.     init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8);
  99.     return !ff_flac_decode_frame_header(avctx, &gb, fi, 127);
  100. }
  101.  
  102. /**
  103.  * Non-destructive fast fifo pointer fetching
  104.  * Returns a pointer from the specified offset.
  105.  * If possible the pointer points within the fifo buffer.
  106.  * Otherwise (if it would cause a wrap around,) a pointer to a user-specified
  107.  * buffer is used.
  108.  * The pointer can be NULL.  In any case it will be reallocated to hold the size.
  109.  * If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
  110.  * then the subsequent calls should pass in a different wrap_buf so as to not
  111.  * overwrite the contents of the previous wrap_buf.
  112.  * This function is based on av_fifo_generic_read, which is why there is a comment
  113.  * about a memory barrier for SMP.
  114.  */
  115. static uint8_t* flac_fifo_read_wrap(FLACParseContext *fpc, int offset, int len,
  116.                                uint8_t** wrap_buf, int* allocated_size)
  117. {
  118.     AVFifoBuffer *f   = fpc->fifo_buf;
  119.     uint8_t *start    = f->rptr + offset;
  120.     uint8_t *tmp_buf;
  121.  
  122.     if (start >= f->end)
  123.         start -= f->end - f->buffer;
  124.     if (f->end - start >= len)
  125.         return start;
  126.  
  127.     tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
  128.  
  129.     if (!tmp_buf) {
  130.         av_log(fpc->avctx, AV_LOG_ERROR,
  131.                "couldn't reallocate wrap buffer of size %d", len);
  132.         return NULL;
  133.     }
  134.     *wrap_buf = tmp_buf;
  135.     do {
  136.         int seg_len = FFMIN(f->end - start, len);
  137.         memcpy(tmp_buf, start, seg_len);
  138.         tmp_buf = (uint8_t*)tmp_buf + seg_len;
  139. // memory barrier needed for SMP here in theory
  140.  
  141.         start += seg_len - (f->end - f->buffer);
  142.         len -= seg_len;
  143.     } while (len > 0);
  144.  
  145.     return *wrap_buf;
  146. }
  147.  
  148. /**
  149.  * Return a pointer in the fifo buffer where the offset starts at until
  150.  * the wrap point or end of request.
  151.  * len will contain the valid length of the returned buffer.
  152.  * A second call to flac_fifo_read (with new offset and len) should be called
  153.  * to get the post-wrap buf if the returned len is less than the requested.
  154.  **/
  155. static uint8_t* flac_fifo_read(FLACParseContext *fpc, int offset, int *len)
  156. {
  157.     AVFifoBuffer *f   = fpc->fifo_buf;
  158.     uint8_t *start    = f->rptr + offset;
  159.  
  160.     if (start >= f->end)
  161.         start -= f->end - f->buffer;
  162.     *len = FFMIN(*len, f->end - start);
  163.     return start;
  164. }
  165.  
  166. static int find_headers_search_validate(FLACParseContext *fpc, int offset)
  167. {
  168.     FLACFrameInfo fi;
  169.     uint8_t *header_buf;
  170.     int size = 0;
  171.     header_buf = flac_fifo_read_wrap(fpc, offset,
  172.                                      MAX_FRAME_HEADER_SIZE,
  173.                                      &fpc->wrap_buf,
  174.                                      &fpc->wrap_buf_allocated_size);
  175.     if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
  176.         FLACHeaderMarker **end_handle = &fpc->headers;
  177.         int i;
  178.  
  179.         size = 0;
  180.         while (*end_handle) {
  181.             end_handle = &(*end_handle)->next;
  182.             size++;
  183.         }
  184.  
  185.         *end_handle = av_mallocz(sizeof(**end_handle));
  186.         if (!*end_handle) {
  187.             av_log(fpc->avctx, AV_LOG_ERROR,
  188.                    "couldn't allocate FLACHeaderMarker\n");
  189.             return AVERROR(ENOMEM);
  190.         }
  191.         (*end_handle)->fi           = fi;
  192.         (*end_handle)->offset       = offset;
  193.         (*end_handle)->link_penalty = av_malloc(sizeof(int) *
  194.                                             FLAC_MAX_SEQUENTIAL_HEADERS);
  195.         if (!(*end_handle)->link_penalty) {
  196.             av_freep(end_handle);
  197.             av_log(fpc->avctx, AV_LOG_ERROR,
  198.                    "couldn't allocate link_penalty\n");
  199.             return AVERROR(ENOMEM);
  200.         }
  201.  
  202.         for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
  203.             (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
  204.  
  205.         fpc->nb_headers_found++;
  206.         size++;
  207.     }
  208.     return size;
  209. }
  210.  
  211. static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size,
  212.                                int search_start)
  213.  
  214. {
  215.     int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
  216.     uint32_t x;
  217.  
  218.     for (i = 0; i < mod_offset; i++) {
  219.         if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
  220.             size = find_headers_search_validate(fpc, search_start + i);
  221.     }
  222.  
  223.     for (; i < buf_size - 1; i += 4) {
  224.         x = AV_RB32(buf + i);
  225.         if (((x & ~(x + 0x01010101)) & 0x80808080)) {
  226.             for (j = 0; j < 4; j++) {
  227.                 if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
  228.                     size = find_headers_search_validate(fpc, search_start + i + j);
  229.             }
  230.         }
  231.     }
  232.     return size;
  233. }
  234.  
  235. static int find_new_headers(FLACParseContext *fpc, int search_start)
  236. {
  237.     FLACHeaderMarker *end;
  238.     int search_end, size = 0, read_len, temp;
  239.     uint8_t *buf;
  240.     fpc->nb_headers_found = 0;
  241.  
  242.     /* Search for a new header of at most 16 bytes. */
  243.     search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
  244.     read_len   = search_end - search_start + 1;
  245.     buf        = flac_fifo_read(fpc, search_start, &read_len);
  246.     size       = find_headers_search(fpc, buf, read_len, search_start);
  247.     search_start += read_len - 1;
  248.  
  249.     /* If fifo end was hit do the wrap around. */
  250.     if (search_start != search_end) {
  251.         uint8_t wrap[2];
  252.  
  253.         wrap[0]  = buf[read_len - 1];
  254.         read_len = search_end - search_start + 1;
  255.  
  256.         /* search_start + 1 is the post-wrap offset in the fifo. */
  257.         buf      = flac_fifo_read(fpc, search_start + 1, &read_len);
  258.         wrap[1]  = buf[0];
  259.  
  260.         if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
  261.             temp = find_headers_search_validate(fpc, search_start);
  262.             size = FFMAX(size, temp);
  263.         }
  264.         search_start++;
  265.  
  266.         /* Continue to do the last half of the wrap. */
  267.         temp     = find_headers_search(fpc, buf, read_len, search_start);
  268.         size     = FFMAX(size, temp);
  269.         search_start += read_len - 1;
  270.     }
  271.  
  272.     /* Return the size even if no new headers were found. */
  273.     if (!size && fpc->headers)
  274.         for (end = fpc->headers; end; end = end->next)
  275.             size++;
  276.     return size;
  277. }
  278.  
  279. static int check_header_fi_mismatch(FLACParseContext  *fpc,
  280.                                     FLACFrameInfo     *header_fi,
  281.                                     FLACFrameInfo     *child_fi,
  282.                                     int                log_level_offset)
  283. {
  284.     int deduction = 0;
  285.     if (child_fi->samplerate != header_fi->samplerate) {
  286.         deduction += FLAC_HEADER_CHANGED_PENALTY;
  287.         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  288.                "sample rate change detected in adjacent frames\n");
  289.     }
  290.     if (child_fi->bps != header_fi->bps) {
  291.         deduction += FLAC_HEADER_CHANGED_PENALTY;
  292.         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  293.                "bits per sample change detected in adjacent frames\n");
  294.     }
  295.     if (child_fi->is_var_size != header_fi->is_var_size) {
  296.         /* Changing blocking strategy not allowed per the spec */
  297.         deduction += FLAC_HEADER_BASE_SCORE;
  298.         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  299.                "blocking strategy change detected in adjacent frames\n");
  300.     }
  301.     if (child_fi->channels != header_fi->channels) {
  302.         deduction += FLAC_HEADER_CHANGED_PENALTY;
  303.         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  304.                "number of channels change detected in adjacent frames\n");
  305.     }
  306.     return deduction;
  307. }
  308.  
  309. static int check_header_mismatch(FLACParseContext  *fpc,
  310.                                  FLACHeaderMarker  *header,
  311.                                  FLACHeaderMarker  *child,
  312.                                  int                log_level_offset)
  313. {
  314.     FLACFrameInfo  *header_fi = &header->fi, *child_fi = &child->fi;
  315.     int deduction, deduction_expected = 0, i;
  316.     deduction = check_header_fi_mismatch(fpc, header_fi, child_fi,
  317.                                          log_level_offset);
  318.     /* Check sample and frame numbers. */
  319.     if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
  320.          != header_fi->blocksize) &&
  321.         (child_fi->frame_or_sample_num
  322.          != header_fi->frame_or_sample_num + 1)) {
  323.         FLACHeaderMarker *curr;
  324.         int expected_frame_num, expected_sample_num;
  325.         /* If there are frames in the middle we expect this deduction,
  326.            as they are probably valid and this one follows it */
  327.  
  328.         expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
  329.         curr = header;
  330.         while (curr != child) {
  331.             /* Ignore frames that failed all crc checks */
  332.             for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
  333.                 if (curr->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY) {
  334.                     expected_frame_num++;
  335.                     expected_sample_num += curr->fi.blocksize;
  336.                     break;
  337.                 }
  338.             }
  339.             curr = curr->next;
  340.         }
  341.  
  342.         if (expected_frame_num  == child_fi->frame_or_sample_num ||
  343.             expected_sample_num == child_fi->frame_or_sample_num)
  344.             deduction_expected = deduction ? 0 : 1;
  345.  
  346.         deduction += FLAC_HEADER_CHANGED_PENALTY;
  347.         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  348.                    "sample/frame number mismatch in adjacent frames\n");
  349.     }
  350.  
  351.     /* If we have suspicious headers, check the CRC between them */
  352.     if (deduction && !deduction_expected) {
  353.         FLACHeaderMarker *curr;
  354.         int read_len;
  355.         uint8_t *buf;
  356.         uint32_t crc = 1;
  357.         int inverted_test = 0;
  358.  
  359.         /* Since CRC is expensive only do it if we haven't yet.
  360.            This assumes a CRC penalty is greater than all other check penalties */
  361.         curr = header->next;
  362.         for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
  363.             curr = curr->next;
  364.  
  365.         if (header->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY ||
  366.             header->link_penalty[i] == FLAC_HEADER_NOT_PENALIZED_YET) {
  367.             FLACHeaderMarker *start, *end;
  368.  
  369.             /* Although overlapping chains are scored, the crc should never
  370.                have to be computed twice for a single byte. */
  371.             start = header;
  372.             end   = child;
  373.             if (i > 0 &&
  374.                 header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
  375.                 while (start->next != child)
  376.                     start = start->next;
  377.                 inverted_test = 1;
  378.             } else if (i > 0 &&
  379.                        header->next->link_penalty[i-1] >=
  380.                        FLAC_HEADER_CRC_FAIL_PENALTY ) {
  381.                 end = header->next;
  382.                 inverted_test = 1;
  383.             }
  384.  
  385.             read_len = end->offset - start->offset;
  386.             buf      = flac_fifo_read(fpc, start->offset, &read_len);
  387.             crc      = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
  388.             read_len = (end->offset - start->offset) - read_len;
  389.  
  390.             if (read_len) {
  391.                 buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
  392.                 crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
  393.             }
  394.         }
  395.  
  396.         if (!crc ^ !inverted_test) {
  397.             deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
  398.             av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  399.                    "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
  400.                    header->offset, header_fi->frame_or_sample_num,
  401.                    child->offset, child_fi->frame_or_sample_num);
  402.         }
  403.     }
  404.     return deduction;
  405. }
  406.  
  407. /**
  408.  * Score a header.
  409.  *
  410.  * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
  411.  * If it has children, (subsequent frames of which the preceding CRC footer
  412.  * validates against this one,) then take the maximum score of the children,
  413.  * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
  414.  * bps, sample rate, channels, but not decorrelation mode, or blocksize,
  415.  * because it can change often.
  416.  **/
  417. static int score_header(FLACParseContext *fpc, FLACHeaderMarker *header)
  418. {
  419.     FLACHeaderMarker *child;
  420.     int dist = 0;
  421.     int child_score;
  422.     int base_score = FLAC_HEADER_BASE_SCORE;
  423.     if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
  424.         return header->max_score;
  425.  
  426.     /* Modify the base score with changes from the last output header */
  427.     if (fpc->last_fi_valid) {
  428.         /* Silence the log since this will be repeated if selected */
  429.         base_score -= check_header_fi_mismatch(fpc, &fpc->last_fi, &header->fi,
  430.                                                AV_LOG_DEBUG);
  431.     }
  432.  
  433.     header->max_score = base_score;
  434.  
  435.     /* Check and compute the children's scores. */
  436.     child = header->next;
  437.     for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
  438.         /* Look at the child's frame header info and penalize suspicious
  439.            changes between the headers. */
  440.         if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
  441.             header->link_penalty[dist] = check_header_mismatch(fpc, header,
  442.                                                                child, AV_LOG_DEBUG);
  443.         }
  444.         child_score = score_header(fpc, child) - header->link_penalty[dist];
  445.  
  446.         if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
  447.             /* Keep the child because the frame scoring is dynamic. */
  448.             header->best_child = child;
  449.             header->max_score  = base_score + child_score;
  450.         }
  451.         child = child->next;
  452.     }
  453.  
  454.     return header->max_score;
  455. }
  456.  
  457. static void score_sequences(FLACParseContext *fpc)
  458. {
  459.     FLACHeaderMarker *curr;
  460.     int best_score = 0;//FLAC_HEADER_NOT_SCORED_YET;
  461.     /* First pass to clear all old scores. */
  462.     for (curr = fpc->headers; curr; curr = curr->next)
  463.         curr->max_score = FLAC_HEADER_NOT_SCORED_YET;
  464.  
  465.     /* Do a second pass to score them all. */
  466.     for (curr = fpc->headers; curr; curr = curr->next) {
  467.         if (score_header(fpc, curr) > best_score) {
  468.             fpc->best_header = curr;
  469.             best_score       = curr->max_score;
  470.         }
  471.     }
  472. }
  473.  
  474. static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf,
  475.                            int *poutbuf_size)
  476. {
  477.     FLACHeaderMarker *header = fpc->best_header;
  478.     FLACHeaderMarker *child  = header->best_child;
  479.     if (!child) {
  480.         *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
  481.     } else {
  482.         *poutbuf_size = child->offset - header->offset;
  483.  
  484.         /* If the child has suspicious changes, log them */
  485.         check_header_mismatch(fpc, header, child, 0);
  486.     }
  487.  
  488.     if (header->fi.channels != fpc->avctx->channels ||
  489.         !fpc->avctx->channel_layout) {
  490.         fpc->avctx->channels = header->fi.channels;
  491.         ff_flac_set_channel_layout(fpc->avctx);
  492.     }
  493.     fpc->avctx->sample_rate = header->fi.samplerate;
  494.     fpc->pc->duration       = header->fi.blocksize;
  495.     *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
  496.                                         &fpc->wrap_buf,
  497.                                         &fpc->wrap_buf_allocated_size);
  498.  
  499.  
  500.     if (fpc->pc->flags & PARSER_FLAG_USE_CODEC_TS){
  501.         if (header->fi.is_var_size)
  502.           fpc->pc->pts = header->fi.frame_or_sample_num;
  503.         else if (header->best_child)
  504.           fpc->pc->pts = header->fi.frame_or_sample_num * header->fi.blocksize;
  505.     }
  506.  
  507.     fpc->best_header_valid = 0;
  508.     fpc->last_fi_valid = 1;
  509.     fpc->last_fi = header->fi;
  510.  
  511.     /* Return the negative overread index so the client can compute pos.
  512.        This should be the amount overread to the beginning of the child */
  513.     if (child)
  514.         return child->offset - av_fifo_size(fpc->fifo_buf);
  515.     return 0;
  516. }
  517.  
  518. static int flac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
  519.                       const uint8_t **poutbuf, int *poutbuf_size,
  520.                       const uint8_t *buf, int buf_size)
  521. {
  522.     FLACParseContext *fpc = s->priv_data;
  523.     FLACHeaderMarker *curr;
  524.     int nb_headers;
  525.     const uint8_t *read_end   = buf;
  526.     const uint8_t *read_start = buf;
  527.  
  528.     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
  529.         FLACFrameInfo fi;
  530.         if (frame_header_is_valid(avctx, buf, &fi)) {
  531.             s->duration = fi.blocksize;
  532.             if (!avctx->sample_rate)
  533.                 avctx->sample_rate = fi.samplerate;
  534.             if (fpc->pc->flags & PARSER_FLAG_USE_CODEC_TS){
  535.                 fpc->pc->pts = fi.frame_or_sample_num;
  536.                 if (!fi.is_var_size)
  537.                   fpc->pc->pts *= fi.blocksize;
  538.             }
  539.         }
  540.         *poutbuf      = buf;
  541.         *poutbuf_size = buf_size;
  542.         return buf_size;
  543.     }
  544.  
  545.     fpc->avctx = avctx;
  546.     if (fpc->best_header_valid)
  547.         return get_best_header(fpc, poutbuf, poutbuf_size);
  548.  
  549.     /* If a best_header was found last call remove it with the buffer data. */
  550.     if (fpc->best_header && fpc->best_header->best_child) {
  551.         FLACHeaderMarker *temp;
  552.         FLACHeaderMarker *best_child = fpc->best_header->best_child;
  553.  
  554.         /* Remove headers in list until the end of the best_header. */
  555.         for (curr = fpc->headers; curr != best_child; curr = temp) {
  556.             if (curr != fpc->best_header) {
  557.                 av_log(avctx, AV_LOG_DEBUG,
  558.                        "dropping low score %i frame header from offset %i to %i\n",
  559.                        curr->max_score, curr->offset, curr->next->offset);
  560.             }
  561.             temp = curr->next;
  562.             av_freep(&curr->link_penalty);
  563.             av_free(curr);
  564.             fpc->nb_headers_buffered--;
  565.         }
  566.         /* Release returned data from ring buffer. */
  567.         av_fifo_drain(fpc->fifo_buf, best_child->offset);
  568.  
  569.         /* Fix the offset for the headers remaining to match the new buffer. */
  570.         for (curr = best_child->next; curr; curr = curr->next)
  571.             curr->offset -= best_child->offset;
  572.  
  573.         fpc->nb_headers_buffered--;
  574.         best_child->offset = 0;
  575.         fpc->headers       = best_child;
  576.         if (fpc->nb_headers_buffered >= FLAC_MIN_HEADERS) {
  577.             fpc->best_header = best_child;
  578.             return get_best_header(fpc, poutbuf, poutbuf_size);
  579.         }
  580.         fpc->best_header   = NULL;
  581.     } else if (fpc->best_header) {
  582.         /* No end frame no need to delete the buffer; probably eof */
  583.         FLACHeaderMarker *temp;
  584.  
  585.         for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
  586.             temp = curr->next;
  587.             av_freep(&curr->link_penalty);
  588.             av_free(curr);
  589.         }
  590.         fpc->headers = fpc->best_header->next;
  591.         av_freep(&fpc->best_header->link_penalty);
  592.         av_freep(&fpc->best_header);
  593.     }
  594.  
  595.     /* Find and score new headers.                                     */
  596.     /* buf_size is to zero when padding, so check for this since we do */
  597.     /* not want to try to read more input once we have found the end.  */
  598.     /* Note that as (non-modified) parameters, buf can be non-NULL,    */
  599.     /* while buf_size is 0.                                            */
  600.     while ((buf && buf_size && read_end < buf + buf_size &&
  601.             fpc->nb_headers_buffered < FLAC_MIN_HEADERS)
  602.            || ((!buf || !buf_size) && !fpc->end_padded)) {
  603.         int start_offset;
  604.  
  605.         /* Pad the end once if EOF, to check the final region for headers. */
  606.         if (!buf || !buf_size) {
  607.             fpc->end_padded      = 1;
  608.             buf_size = MAX_FRAME_HEADER_SIZE;
  609.             read_end = read_start + MAX_FRAME_HEADER_SIZE;
  610.         } else {
  611.             /* The maximum read size is the upper-bound of what the parser
  612.                needs to have the required number of frames buffered */
  613.             int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1;
  614.             read_end       = read_end + FFMIN(buf + buf_size - read_end,
  615.                                               nb_desired * FLAC_AVG_FRAME_SIZE);
  616.         }
  617.  
  618.         if (!av_fifo_space(fpc->fifo_buf) &&
  619.             av_fifo_size(fpc->fifo_buf) / FLAC_AVG_FRAME_SIZE >
  620.             fpc->nb_headers_buffered * 10) {
  621.             /* There is less than one valid flac header buffered for 10 headers
  622.              * buffered. Therefore the fifo is most likely filled with invalid
  623.              * data and the input is not a flac file. */
  624.             goto handle_error;
  625.         }
  626.  
  627.         /* Fill the buffer. */
  628.         if (   av_fifo_space(fpc->fifo_buf) < read_end - read_start
  629.             && av_fifo_realloc2(fpc->fifo_buf, (read_end - read_start) + 2*av_fifo_size(fpc->fifo_buf)) < 0) {
  630.             av_log(avctx, AV_LOG_ERROR,
  631.                    "couldn't reallocate buffer of size %"PTRDIFF_SPECIFIER"\n",
  632.                    (read_end - read_start) + av_fifo_size(fpc->fifo_buf));
  633.             goto handle_error;
  634.         }
  635.  
  636.         if (buf && buf_size) {
  637.             av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
  638.                                   read_end - read_start, NULL);
  639.         } else {
  640.             int8_t pad[MAX_FRAME_HEADER_SIZE] = { 0 };
  641.             av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL);
  642.         }
  643.  
  644.         /* Tag headers and update sequences. */
  645.         start_offset = av_fifo_size(fpc->fifo_buf) -
  646.                        ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));
  647.         start_offset = FFMAX(0, start_offset);
  648.         nb_headers   = find_new_headers(fpc, start_offset);
  649.  
  650.         if (nb_headers < 0) {
  651.             av_log(avctx, AV_LOG_ERROR,
  652.                    "find_new_headers couldn't allocate FLAC header\n");
  653.             goto handle_error;
  654.         }
  655.  
  656.         fpc->nb_headers_buffered = nb_headers;
  657.         /* Wait till FLAC_MIN_HEADERS to output a valid frame. */
  658.         if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
  659.             if (buf && read_end < buf + buf_size) {
  660.                 read_start = read_end;
  661.                 continue;
  662.             } else {
  663.                 goto handle_error;
  664.             }
  665.         }
  666.  
  667.         /* If headers found, update the scores since we have longer chains. */
  668.         if (fpc->end_padded || fpc->nb_headers_found)
  669.             score_sequences(fpc);
  670.  
  671.         /* restore the state pre-padding */
  672.         if (fpc->end_padded) {
  673.             int warp = fpc->fifo_buf->wptr - fpc->fifo_buf->buffer < MAX_FRAME_HEADER_SIZE;
  674.             /* HACK: drain the tail of the fifo */
  675.             fpc->fifo_buf->wptr -= MAX_FRAME_HEADER_SIZE;
  676.             fpc->fifo_buf->wndx -= MAX_FRAME_HEADER_SIZE;
  677.             if (warp) {
  678.                 fpc->fifo_buf->wptr += fpc->fifo_buf->end -
  679.                     fpc->fifo_buf->buffer;
  680.             }
  681.             buf_size = 0;
  682.             read_start = read_end = NULL;
  683.         }
  684.     }
  685.  
  686.     for (curr = fpc->headers; curr; curr = curr->next) {
  687.         if (curr->max_score > 0 &&
  688.             (!fpc->best_header || curr->max_score > fpc->best_header->max_score)) {
  689.             fpc->best_header = curr;
  690.         }
  691.     }
  692.  
  693.     if (fpc->best_header) {
  694.         fpc->best_header_valid = 1;
  695.         if (fpc->best_header->offset > 0) {
  696.             /* Output a junk frame. */
  697.             av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
  698.                    fpc->best_header->offset);
  699.  
  700.             /* Set duration to 0. It is unknown or invalid in a junk frame. */
  701.             s->duration = 0;
  702.             *poutbuf_size     = fpc->best_header->offset;
  703.             *poutbuf          = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
  704.                                                     &fpc->wrap_buf,
  705.                                                     &fpc->wrap_buf_allocated_size);
  706.             return buf_size ? (read_end - buf) : (fpc->best_header->offset -
  707.                                            av_fifo_size(fpc->fifo_buf));
  708.         }
  709.         if (!buf_size)
  710.             return get_best_header(fpc, poutbuf, poutbuf_size);
  711.     }
  712.  
  713. handle_error:
  714.     *poutbuf      = NULL;
  715.     *poutbuf_size = 0;
  716.     return buf_size ? read_end - buf : 0;
  717. }
  718.  
  719. static av_cold int flac_parse_init(AVCodecParserContext *c)
  720. {
  721.     FLACParseContext *fpc = c->priv_data;
  722.     fpc->pc = c;
  723.     /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
  724.        it drains.  This is allocated early to avoid slow reallocation. */
  725.     fpc->fifo_buf = av_fifo_alloc_array(FLAC_MIN_HEADERS + 3, FLAC_AVG_FRAME_SIZE);
  726.     if (!fpc->fifo_buf) {
  727.         av_log(fpc->avctx, AV_LOG_ERROR,
  728.                 "couldn't allocate fifo_buf\n");
  729.         return AVERROR(ENOMEM);
  730.     }
  731.     return 0;
  732. }
  733.  
  734. static void flac_parse_close(AVCodecParserContext *c)
  735. {
  736.     FLACParseContext *fpc = c->priv_data;
  737.     FLACHeaderMarker *curr = fpc->headers, *temp;
  738.  
  739.     while (curr) {
  740.         temp = curr->next;
  741.         av_freep(&curr->link_penalty);
  742.         av_free(curr);
  743.         curr = temp;
  744.     }
  745.     av_fifo_freep(&fpc->fifo_buf);
  746.     av_freep(&fpc->wrap_buf);
  747. }
  748.  
  749. AVCodecParser ff_flac_parser = {
  750.     .codec_ids      = { AV_CODEC_ID_FLAC },
  751.     .priv_data_size = sizeof(FLACParseContext),
  752.     .parser_init    = flac_parse_init,
  753.     .parser_parse   = flac_parse,
  754.     .parser_close   = flac_parse_close,
  755. };
  756.