C++ (Cpp) av_build_filter示例

示例#1

文件： resample2.c 项目： pcercuei/dcplaya

/**
 * initalizes a audio resampler.
 * note, if either rate is not a integer then simply scale both rates up so they are
 */
AVResampleContext *av_resample_init(int out_rate, int in_rate){
    AVResampleContext *c= av_mallocz(sizeof(AVResampleContext));
    double factor= FFMIN(out_rate / (double)in_rate, 1.0);

    memset(c, 0, sizeof(AVResampleContext));

    c->filter_length= ceil(16.0/factor);
    c->filter_bank= av_mallocz(c->filter_length*(PHASE_COUNT+1)*sizeof(short));
    av_build_filter(c->filter_bank, factor, c->filter_length, PHASE_COUNT, 1<<FILTER_SHIFT, 1);
    c->filter_bank[c->filter_length*PHASE_COUNT + (c->filter_length-1) + 1]= (1<<FILTER_SHIFT)-1;
    c->filter_bank[c->filter_length*PHASE_COUNT + (c->filter_length-1) + 2]= 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;
}

示例#2

文件： resample2.c 项目： lebauce/pulseaudio

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));
    av_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;
}