Add a FLAC parser.

Seek test reference updated because FLAC seeking now works properly.
Fixes roundup issue 1150.

Patch by Michael Chinen [mchinen at gmail]

Originally committed as revision 25914 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 648 insertions, 0 deletions

diff --git a/libavcodec/flac_parser.c b/libavcodec/flac_parser.c
new file mode 100644
index 0000000000..5aeb923406
--- /dev/null
+++ b/libavcodec/flac_parser.c
@@ -0,0 +1,648 @@
+/*
+ * FLAC parser
+ * Copyright (c) 2010 Michael Chinen
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * FLAC parser
+ *
+ * The FLAC parser buffers input until FLAC_MIN_HEADERS has been found.
+ * Each time it finds and verifies a CRC-8 header it sees which of the
+ * FLAC_MAX_SEQUENTIAL_HEADERS that came before it have a valid CRC-16 footer
+ * that ends at the newly found header.
+ * Headers are scored by FLAC_HEADER_BASE_SCORE plus the max of it's crc-verified
+ * children, penalized by changes in sample rate, frame number, etc.
+ * The parser returns the frame with the highest score.
+ **/
+
+#include "libavutil/crc.h"
+#include "libavutil/fifo.h"
+#include "bytestream.h"
+#include "parser.h"
+#include "flac.h"
+
+/** maximum number of adjacent headers that compare CRCs against each other   */
+#define FLAC_MAX_SEQUENTIAL_HEADERS 3
+/** minimum number of headers buffered and checked before returning frames    */
+#define FLAC_MIN_HEADERS 10
+
+/** scoring settings for score_header */
+#define FLAC_HEADER_BASE_SCORE        10
+#define FLAC_HEADER_CHANGED_PENALTY   7
+#define FLAC_HEADER_CRC_FAIL_PENALTY  50
+#define FLAC_HEADER_NOT_PENALIZED_YET 100000
+#define FLAC_HEADER_NOT_SCORED_YET    -100000
+
+/** largest possible size of flac header */
+#define MAX_FRAME_HEADER_SIZE 16
+
+typedef struct FLACHeaderMarker {
+    int offset;       /**< byte offset from start of FLACParseContext->buffer */
+    int *link_penalty;  /**< pointer to array of local scores between this header
+                           and the one at a distance equal array position     */
+    int max_score;    /**< maximum score found after checking each child that
+                           has a valid CRC                                    */
+    FLACFrameInfo fi; /**< decoded frame header info                          */
+    struct FLACHeaderMarker *next;       /**< next CRC-8 verified header that
+                                              immediately follows this one in
+                                              the bytestream                  */
+    struct FLACHeaderMarker *best_child; /**< following frame header with
+                                              which this frame has the best
+                                              score with                      */
+} FLACHeaderMarker;
+
+typedef struct FLACParseContext {
+    AVCodecContext *avctx;         /**< codec context pointer for logging     */
+    FLACHeaderMarker *headers;     /**< linked-list that starts at the first
+                                        CRC-8 verified header within buffer   */
+    FLACHeaderMarker *best_header; /**< highest scoring header within buffer  */
+    int nb_headers_found;          /**< number of headers found in the last
+                                        flac_parse() call                     */
+    int best_header_valid;         /**< flag set when the parser returns junk;
+                                        if set return best_header next time   */
+    AVFifoBuffer *fifo_buf;        /**< buffer to store all data until headers
+                                        can be verified                       */
+    int end_padded;                /**< specifies if fifo_buf's end is padded */
+    uint8_t *wrap_buf;             /**< general fifo read buffer when wrapped */
+    int wrap_buf_allocated_size;   /**< actual allocated size of the buffer   */
+} FLACParseContext;
+
+static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
+                                 FLACFrameInfo *fi)
+{
+    GetBitContext gb;
+    init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8);
+    return !ff_flac_decode_frame_header(avctx, &gb, fi, 127);
+}
+
+/**
+ * Non-destructive fast fifo pointer fetching
+ * Returns a pointer from the specified offset.
+ * If possible the pointer points within the fifo buffer.
+ * Otherwise (if it would cause a wrap around,) a pointer to a user-specified
+ * buffer is used.
+ * The pointer can be NULL.  In any case it will be reallocated to hold the size.
+ * If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
+ * then the subsequent calls should pass in a different wrap_buf so as to not
+ * overwrite the contents of the previous wrap_buf.
+ * This function is based on av_fifo_generic_read, which is why there is a comment
+ * about a memory barrier for SMP.
+ */
+static uint8_t* flac_fifo_read_wrap(FLACParseContext *fpc, int offset, int len,
+                               uint8_t** wrap_buf, int* allocated_size)
+{
+    AVFifoBuffer *f   = fpc->fifo_buf;
+    uint8_t *start    = f->rptr + offset;
+    uint8_t *tmp_buf;
+
+    if (start >= f->end)
+        start -= f->end - f->buffer;
+    if (f->end - start >= len)
+        return start;
+
+    tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
+
+    if (!tmp_buf) {
+        av_log(fpc->avctx, AV_LOG_ERROR,
+               "couldn't reallocate wrap buffer of size %d", len);
+        return NULL;
+    }
+    *wrap_buf = tmp_buf;
+    do {
+        int seg_len = FFMIN(f->end - start, len);
+        memcpy(tmp_buf, start, seg_len);
+        tmp_buf = (uint8_t*)tmp_buf + seg_len;
+// memory barrier needed for SMP here in theory
+
+        start += seg_len - (f->end - f->buffer);
+        len -= seg_len;
+    } while (len > 0);
+
+    return *wrap_buf;
+}
+
+/**
+ * Return a pointer in the fifo buffer where the offset starts at until
+ * the wrap point or end of request.
+ * len will contain the valid length of the returned buffer.
+ * A second call to flac_fifo_read (with new offset and len) should be called
+ * to get the post-wrap buf if the returned len is less than the requested.
+ **/
+static uint8_t* flac_fifo_read(FLACParseContext *fpc, int offset, int *len)
+{
+    AVFifoBuffer *f   = fpc->fifo_buf;
+    uint8_t *start    = f->rptr + offset;
+
+    if (start >= f->end)
+        start -= f->end - f->buffer;
+    *len = FFMIN(*len, f->end - start);
+    return start;
+}
+
+static int find_headers_search_validate(FLACParseContext *fpc, int offset)
+{
+    FLACFrameInfo fi;
+    uint8_t *header_buf;
+    int size = 0;
+    header_buf = flac_fifo_read_wrap(fpc, offset,
+                                     MAX_FRAME_HEADER_SIZE,
+                                     &fpc->wrap_buf,
+                                     &fpc->wrap_buf_allocated_size);
+    if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
+        FLACHeaderMarker **end_handle = &fpc->headers;
+        int i;
+
+        size = 0;
+        while (*end_handle) {
+            end_handle = &(*end_handle)->next;
+            size++;
+        }
+
+        *end_handle = av_mallocz(sizeof(FLACHeaderMarker));
+        if (!*end_handle) {
+            av_log(fpc->avctx, AV_LOG_ERROR,
+                   "couldn't allocate FLACHeaderMarker\n");
+            return AVERROR(ENOMEM);
+        }
+        (*end_handle)->fi           = fi;
+        (*end_handle)->offset       = offset;
+        (*end_handle)->link_penalty = av_malloc(sizeof(int) *
+                                            FLAC_MAX_SEQUENTIAL_HEADERS);
+        for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
+            (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
+
+        fpc->nb_headers_found++;
+        size++;
+    }
+    return size;
+}
+
+static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size,
+                               int search_start)
+
+{
+    int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
+    uint32_t x;
+
+    for (i = 0; i < mod_offset; i++) {
+        if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
+            size = find_headers_search_validate(fpc, search_start + i);
+    }
+
+    for (; i < buf_size - 1; i += 4) {
+        x = AV_RB32(buf + i);
+        if (((x & ~(x + 0x01010101)) & 0x80808080)) {
+            for (j = 0; j < 4; j++) {
+                if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
+                    size = find_headers_search_validate(fpc, search_start + i + j);
+            }
+        }
+    }
+    return size;
+}
+
+static int find_new_headers(FLACParseContext *fpc, int search_start)
+{
+    FLACHeaderMarker *end;
+    int search_end, size = 0, read_len, temp;
+    uint8_t *buf;
+    fpc->nb_headers_found = 0;
+
+    /* Search for a new header of at most 16 bytes. */
+    search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
+    read_len   = search_end - search_start + 1;
+    buf        = flac_fifo_read(fpc, search_start, &read_len);
+    size       = find_headers_search(fpc, buf, read_len, search_start);
+    search_start += read_len - 1;
+
+    /* If fifo end was hit do the wrap around. */
+    if (search_start != search_end) {
+        uint8_t wrap[2];
+
+        wrap[0]  = buf[read_len - 1];
+        read_len = search_end - search_start + 1;
+
+        /* search_start + 1 is the post-wrap offset in the fifo. */
+        buf      = flac_fifo_read(fpc, search_start + 1, &read_len);
+        wrap[1]  = buf[0];
+
+        if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
+            temp = find_headers_search_validate(fpc, search_start);
+            size = FFMAX(size, temp);
+        }
+        search_start++;
+
+        /* Continue to do the last half of the wrap. */
+        temp     = find_headers_search(fpc, buf, read_len, search_start);
+        size     = FFMAX(size, temp);
+        search_start += read_len - 1;
+    }
+
+    /* Return the size even if no new headers were found. */
+    if (!size && fpc->headers)
+        for (end = fpc->headers; end; end = end->next)
+            size++;
+    return size;
+}
+
+static int check_header_mismatch(FLACParseContext  *fpc,
+                                 FLACHeaderMarker  *header,
+                                 FLACHeaderMarker  *child,
+                                 int                log_level_offset)
+{
+    FLACFrameInfo  *header_fi = &header->fi, *child_fi = &child->fi;
+    int deduction = 0, deduction_expected = 0, i;
+    if (child_fi->samplerate != header_fi->samplerate) {
+        deduction += FLAC_HEADER_CHANGED_PENALTY;
+        av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
+               "sample rate change detected in adjacent frames\n");
+    }
+    if (child_fi->bps != header_fi->bps) {
+        deduction += FLAC_HEADER_CHANGED_PENALTY;
+        av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
+               "bits per sample change detected in adjacent frames\n");
+    }
+    if (child_fi->is_var_size != header_fi->is_var_size) {
+        /* Changing blocking strategy not allowed per the spec */
+        deduction += FLAC_HEADER_BASE_SCORE;
+        av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
+                   "blocking strategy change detected in adjacent frames\n");
+    }
+    if (child_fi->channels != header_fi->channels) {
+        deduction += FLAC_HEADER_CHANGED_PENALTY;
+        av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
+                   "number of channels change detected in adjacent frames\n");
+    }
+    /* Check sample and frame numbers. */
+    if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
+         != header_fi->blocksize) &&
+        (child_fi->frame_or_sample_num
+         != header_fi->frame_or_sample_num + 1)) {
+        FLACHeaderMarker *curr;
+        int expected_frame_num, expected_sample_num;
+        /* If there are frames in the middle we expect this deduction,
+           as they are probably valid and this one follows it */
+
+        expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
+        curr = header;
+        while (curr != child) {
+            /* Ignore frames that failed all crc checks */
+            for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
+                if (curr->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY) {
+                    expected_frame_num++;
+                    expected_sample_num += curr->fi.blocksize;
+                    break;
+                }
+            }
+            curr = curr->next;
+        }
+
+        if (expected_frame_num  == child_fi->frame_or_sample_num ||
+            expected_sample_num == child_fi->frame_or_sample_num)
+            deduction_expected = deduction ? 0 : 1;
+
+        deduction += FLAC_HEADER_CHANGED_PENALTY;
+        av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
+                   "sample/frame number mismatch in adjacent frames\n");
+    }
+
+    /* If we have suspicious headers, check the CRC between them */
+    if (deduction && !deduction_expected) {
+        FLACHeaderMarker *curr;
+        int read_len;
+        uint8_t *buf;
+        uint32_t crc = 1;
+        int inverted_test = 0;
+
+        /* Since CRC is expensive only do it if we haven't yet.
+           This assumes a CRC penalty is greater than all other check penalties */
+        curr = header->next;
+        for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
+            curr = curr->next;
+
+        if (header->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY ||
+            header->link_penalty[i] == FLAC_HEADER_NOT_PENALIZED_YET) {
+            FLACHeaderMarker *start, *end;
+
+            /* Although overlapping chains are scored, the crc should never
+               have to be computed twice for a single byte. */
+            start = header;
+            end   = child;
+            if (i > 0 &&
+                header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
+                while (start->next != child)
+                    start = start->next;
+                inverted_test = 1;
+            } else if (i > 0 &&
+                       header->next->link_penalty[i-1] >=
+                       FLAC_HEADER_CRC_FAIL_PENALTY ) {
+                end = header->next;
+                inverted_test = 1;
+            }
+
+            read_len = end->offset - start->offset;
+            buf      = flac_fifo_read(fpc, start->offset, &read_len);
+            crc      = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
+            read_len = (end->offset - start->offset) - read_len;
+
+            if (read_len) {
+                buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
+                crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
+            }
+        }
+
+        if (!crc ^ !inverted_test) {
+            deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
+            av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
+                   "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
+                   header->offset, header_fi->frame_or_sample_num,
+                   child->offset, child_fi->frame_or_sample_num);
+        }
+    }
+    return deduction;
+}
+
+/**
+ * Score a header.
+ *
+ * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
+ * If it has children, (subsequent frames of which the preceding CRC footer
+ * validates against this one,) then take the maximum score of the children,
+ * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
+ * bps, sample rate, channels, but not decorrelation mode, or blocksize,
+ * because it can change often.
+ **/
+static int score_header(FLACParseContext *fpc, FLACHeaderMarker *header)
+{
+    FLACHeaderMarker *child;
+    int dist = 0;
+    int child_score;
+
+    if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
+        return header->max_score;
+
+    header->max_score = FLAC_HEADER_BASE_SCORE;
+
+    /* Check and compute the children's scores. */
+    child = header->next;
+    for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
+        /* Look at the child's frame header info and penalize suspicious
+           changes between the headers. */
+        if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
+            header->link_penalty[dist] = check_header_mismatch(fpc, header,
+                                                               child, AV_LOG_DEBUG);
+        }
+        child_score = score_header(fpc, child) - header->link_penalty[dist];
+
+        if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
+            /* Keep the child because the frame scoring is dynamic. */
+            header->best_child = child;
+            header->max_score  = FLAC_HEADER_BASE_SCORE + child_score;
+        }
+        child = child->next;
+    }
+
+    return header->max_score;
+}
+
+static void score_sequences(FLACParseContext *fpc)
+{
+    FLACHeaderMarker *curr;
+    int best_score = FLAC_HEADER_NOT_SCORED_YET;
+    /* First pass to clear all old scores. */
+    for (curr = fpc->headers; curr; curr = curr->next)
+        curr->max_score = FLAC_HEADER_NOT_SCORED_YET;
+
+    /* Do a second pass to score them all. */
+    for (curr = fpc->headers; curr; curr = curr->next) {
+        if (score_header(fpc, curr) > best_score) {
+            fpc->best_header = curr;
+            best_score       = curr->max_score;
+        }
+    }
+}
+
+static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf,
+                           int *poutbuf_size)
+{
+    FLACHeaderMarker *header = fpc->best_header;
+    FLACHeaderMarker *child  = header->best_child;
+    if (!child) {
+        *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
+    } else {
+        *poutbuf_size = child->offset - header->offset;
+
+        /* If the child has suspicious changes, log them */
+        check_header_mismatch(fpc, header, child, 0);
+    }
+
+    fpc->avctx->sample_rate = header->fi.samplerate;
+    fpc->avctx->channels    = header->fi.channels;
+    fpc->avctx->frame_size  = header->fi.blocksize;
+    *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
+                                        &fpc->wrap_buf,
+                                        &fpc->wrap_buf_allocated_size);
+
+    fpc->best_header_valid = 0;
+    /* Return the negative overread index so the client can compute pos.
+       This should be the amount overread to the beginning of the child */
+    if (child)
+        return child->offset - av_fifo_size(fpc->fifo_buf);
+    return 0;
+}
+
+static int flac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
+                      const uint8_t **poutbuf, int *poutbuf_size,
+                      const uint8_t *buf, int buf_size)
+{
+    FLACParseContext *fpc = s->priv_data;
+    FLACHeaderMarker *curr;
+    int nb_headers;
+
+    if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
+        FLACFrameInfo fi;
+        if (frame_header_is_valid(avctx, buf, &fi))
+            avctx->frame_size = fi.blocksize;
+        *poutbuf      = buf;
+        *poutbuf_size = buf_size;
+        return buf_size;
+    }
+
+    fpc->avctx = avctx;
+    if (fpc->best_header_valid)
+        return get_best_header(fpc, poutbuf, poutbuf_size);
+
+    /* If a best_header was found last call remove it with the buffer data. */
+    if (fpc->best_header && fpc->best_header->best_child) {
+        FLACHeaderMarker *temp;
+        FLACHeaderMarker *best_child = fpc->best_header->best_child;
+
+        /* Remove headers in list until the end of the best_header. */
+        for (curr = fpc->headers; curr != best_child; curr = temp) {
+            if (curr != fpc->best_header) {
+                av_log(avctx, AV_LOG_DEBUG,
+                       "dropping low score %i frame header from offset %i to %i\n",
+                       curr->max_score, curr->offset, curr->next->offset);
+            }
+            temp = curr->next;
+            av_freep(&curr->link_penalty);
+            av_free(curr);
+        }
+        /* Release returned data from ring buffer. */
+        av_fifo_drain(fpc->fifo_buf, best_child->offset);
+
+        /* Fix the offset for the headers remaining to match the new buffer. */
+        for (curr = best_child->next; curr; curr = curr->next)
+            curr->offset -= best_child->offset;
+
+        best_child->offset = 0;
+        fpc->headers       = best_child;
+        fpc->best_header   = NULL;
+    } else if (fpc->best_header) {
+        /* No end frame no need to delete the buffer; probably eof */
+        FLACHeaderMarker *temp;
+
+        for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
+            temp = curr->next;
+            av_freep(&curr->link_penalty);
+            av_free(curr);
+        }
+        fpc->headers = fpc->best_header->next;
+        av_freep(&fpc->best_header->link_penalty);
+        av_freep(&fpc->best_header);
+    }
+
+    /* Find and score new headers. */
+    if (buf_size || !fpc->end_padded) {
+        int start_offset;
+
+        /* Pad the end once if EOF, to check the final region for headers. */
+        if (!buf_size) {
+            fpc->end_padded = 1;
+            buf_size        = MAX_FRAME_HEADER_SIZE;
+        }
+
+        /* Fill the buffer. */
+        if (av_fifo_realloc2(fpc->fifo_buf,
+                             buf_size + av_fifo_size(fpc->fifo_buf)) < 0) {
+            av_log(avctx, AV_LOG_ERROR,
+                   "couldn't reallocate buffer of size %d\n",
+                   buf_size + av_fifo_size(fpc->fifo_buf));
+            goto handle_error;
+        }
+
+        if (buf) {
+            av_fifo_generic_write(fpc->fifo_buf, (void*) buf, buf_size, NULL);
+        } else {
+            int8_t pad[MAX_FRAME_HEADER_SIZE];
+            memset(pad, 0, sizeof(pad));
+            av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL);
+        }
+
+        /* Tag headers and update sequences. */
+        start_offset = av_fifo_size(fpc->fifo_buf) -
+                       (buf_size + (MAX_FRAME_HEADER_SIZE - 1));
+        start_offset = FFMAX(0, start_offset);
+        nb_headers   = find_new_headers(fpc, start_offset);
+
+        /* Wait till FLAC_MIN_HEADERS to output a valid frame. */
+        if (!fpc->end_padded && nb_headers < FLAC_MIN_HEADERS)
+            goto handle_error;
+
+        /* If headers found, update the scores since we have longer chains. */
+        if (fpc->end_padded || fpc->nb_headers_found)
+            score_sequences(fpc);
+
+        /* restore the state pre-padding */
+        if (fpc->end_padded) {
+            /* HACK: drain the tail of the fifo */
+            fpc->fifo_buf->wptr -= MAX_FRAME_HEADER_SIZE;
+            fpc->fifo_buf->wndx -= MAX_FRAME_HEADER_SIZE;
+            if (fpc->fifo_buf->wptr < 0) {
+                fpc->fifo_buf->wptr += fpc->fifo_buf->end -
+                    fpc->fifo_buf->buffer;
+            }
+            buf_size = 0;
+        }
+    }
+
+    curr = fpc->headers;
+    for (curr = fpc->headers; curr; curr = curr->next)
+        if (!fpc->best_header || curr->max_score > fpc->best_header->max_score)
+            fpc->best_header = curr;
+
+    if (fpc->best_header) {
+        fpc->best_header_valid = 1;
+        if (fpc->best_header->offset > 0) {
+            /* Output a junk frame. */
+            av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
+                   fpc->best_header->offset);
+
+            /* Set frame_size to 0. It is unknown or invalid in a junk frame. */
+            avctx->frame_size = 0;
+            *poutbuf_size     = fpc->best_header->offset;
+            *poutbuf          = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
+                                                    &fpc->wrap_buf,
+                                                    &fpc->wrap_buf_allocated_size);
+            return buf_size ? buf_size : (fpc->best_header->offset -
+                                          av_fifo_size(fpc->fifo_buf));
+        }
+        if (!buf_size)
+            return get_best_header(fpc, poutbuf, poutbuf_size);
+    }
+
+handle_error:
+    *poutbuf      = NULL;
+    *poutbuf_size = 0;
+    return buf_size;
+}
+
+static int flac_parse_init(AVCodecParserContext *c)
+{
+    FLACParseContext *fpc = c->priv_data;
+    /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
+       it drains.  8192 is an approximate average size of a flac frame     */
+    fpc->fifo_buf = av_fifo_alloc(8192 * FLAC_MIN_HEADERS);
+
+    return 0;
+}
+
+static void flac_parse_close(AVCodecParserContext *c)
+{
+    FLACParseContext *fpc = c->priv_data;
+    FLACHeaderMarker *curr = fpc->headers, *temp;
+
+    while (curr) {
+        temp = curr->next;
+        av_freep(&curr->link_penalty);
+        av_free(curr);
+        curr = temp;
+    }
+    av_fifo_free(fpc->fifo_buf);
+    av_free(fpc->wrap_buf);
+}
+
+AVCodecParser flac_parser = {
+    { CODEC_ID_FLAC },
+    sizeof(FLACParseContext),
+    flac_parse_init,
+    flac_parse,
+    flac_parse_close,
+};