Function av_resample_init

libavcodec/resample2.c:181–201

}

AVResampleContext *av_resample_init(int out_rate, int in_rate, int filter_size, int phase_shift, int linear, double cutoff){
    AVResampleContext *c= av_mallocz(sizeof(AVResampleContext));
    double factor= FFMIN(out_rate * cutoff / in_rate, 1.0);
    int phase_count= 1<<phase_shift;

    c->phase_shift= phase_shift;
    c->phase_mask= phase_count-1;
    c->linear= linear;

    c->filter_length= FFMAX((int)ceil(filter_size/factor), 1);
    c->filter_bank= av_mallocz(c->filter_length*(phase_count+1)*sizeof(FELEM));
    build_filter(c->filter_bank, factor, c->filter_length, phase_count, 1<<FILTER_SHIFT, WINDOW_TYPE);
    memcpy(&c->filter_bank[c->filter_length*phase_count+1], c->filter_bank, (c->filter_length-1)*sizeof(FELEM));
    c->filter_bank[c->filter_length*phase_count]= c->filter_bank[c->filter_length - 1];

    c->src_incr= out_rate;
    c->ideal_dst_incr= c->dst_incr= in_rate * phase_count;
    c->index= -phase_count*((c->filter_length-1)/2);

    return c;
}

void av_resample_close(AVResampleContext *c){
    av_freep(&c->filter_bank);