/**
* 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 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);
}
if (header->fi.channels != fpc->avctx->channels ||
!fpc->avctx->channel_layout) {
fpc->avctx->channels = header->fi.channels;
ff_flac_set_channel_layout(fpc->avctx);
}
fpc->avctx->sample_rate = header->fi.samplerate;
fpc->pc->duration = 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;
}
/**
* 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;
int base_score = FLAC_HEADER_BASE_SCORE;
if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
return header->max_score;
/* Modify the base score with changes from the last output header */
if (fpc->last_fi_valid) {
/* Silence the log since this will be repeated if selected */
base_score -= check_header_fi_mismatch(fpc, &fpc->last_fi, &header->fi,
AV_LOG_DEBUG);
}
header->max_score = 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 = base_score + child_score;
}
child = child->next;
}
return header->max_score;
}
