Function resample_init

libswresample/resample.c:184–278

}

static ResampleContext *resample_init(ResampleContext *c, int out_rate, int in_rate, int filter_size, int phase_shift, int linear,
                                    double cutoff0, enum AVSampleFormat format, enum SwrFilterType filter_type, double kaiser_beta,
                                    double precision, int cheby, int exact_rational)
{
    double cutoff = cutoff0? cutoff0 : 0.97;
    double factor= FFMIN(out_rate * cutoff / in_rate, 1.0);
    int phase_count= 1<<phase_shift;
    int phase_count_compensation = phase_count;
    int filter_length = FFMAX((int)ceil(filter_size/factor), 1);

    if (filter_length > 1)
        filter_length = FFALIGN(filter_length, 2);

    if (exact_rational) {
        int phase_count_exact, phase_count_exact_den;

        av_reduce(&phase_count_exact, &phase_count_exact_den, out_rate, in_rate, INT_MAX);
        if (phase_count_exact <= phase_count) {
            phase_count_compensation = phase_count_exact * (phase_count / phase_count_exact);
            phase_count = phase_count_exact;
        }
    }

    if (!c || c->phase_count != phase_count || c->linear!=linear || c->factor != factor
           || c->filter_length != filter_length || c->format != format
           || c->filter_type != filter_type || c->kaiser_beta != kaiser_beta) {
        resample_free(&c);
        c = av_mallocz(sizeof(*c));
        if (!c)
            return NULL;

        c->format= format;

        c->felem_size= av_get_bytes_per_sample(c->format);

        switch(c->format){
        case AV_SAMPLE_FMT_S16P:
            c->filter_shift = 15;
            break;
        case AV_SAMPLE_FMT_S32P:
            c->filter_shift = 30;
            break;
        case AV_SAMPLE_FMT_FLTP:
        case AV_SAMPLE_FMT_DBLP:
            c->filter_shift = 0;
            break;
        default:
            av_log(NULL, AV_LOG_ERROR, "Unsupported sample format\n");
            av_assert0(0);
        }

        if (filter_size/factor > INT32_MAX/256) {
            av_log(NULL, AV_LOG_ERROR, "Filter length too large\n");
            goto error;
        }

        c->phase_count   = phase_count;
        c->linear        = linear;