On Fri, Nov 27, 2020 at 7:09 PM Michael Koch <[email protected]> wrote:
> Hello, > > I have a few questions about the asubboost and asupercut filters. > > -- In asubboost it's not yet clear how the block diagram of the filter > looks like. Especially the "decay" and "feedback" options are unclear. > What's the input of the the delay line? Before or after the low pass > filter? Where does the feedback go to? Before or after the lowpass > filter? I have attached a sketch of a possible block diagram, but it's > only a wild guess. > > -- What's the unit of "delay"? Is it milliseconds? Or is it audio samples? > This filter just adds delayed sub frequencies set by cut off frequency back to output. Decay sets decay of old sub echo in buffer and feedback sets how much new sub frequencies are added to the delay buffer. Delay is set in 1/1000 seconds. > > -- Is it correct that the "slope" parameter effectively changes the > cutoff frequency, but doesn't change the steepness (dB / octave) of the > filter? > It changes steepness, not cutoff. > > -- What's the difference between "asupercut" and "lowpass" filter? > What's the filter steepness of the asupercut filter? > Very big, almost under 90 deg. You can find out filter graph response for almost any filter combination in graph. Using this filter graph: mpv av://lavfi:aevalsrc="not(mod(n\,32768)):d=50" -lavfi-complex "[aid1]asupercut,asplit[ao],showfreqs=overlap=0:win_size=32768:win_func=rect:ascale=log,format=rgb0[vo]" In place of asupercut you can put any combinations of FIR and/or IIR filters: lowpass, bandpass, ..., aiir, afir, acrossover and so on. > > Michael > _______________________________________________ > ffmpeg-user mailing list > [email protected] > https://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > [email protected] with subject "unsubscribe". _______________________________________________ ffmpeg-user mailing list [email protected] https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
