예제 #1
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;

    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;
}
예제 #2
0
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;
}
예제 #3
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;
}