On Sat, Nov 28, 2020 at 5:18 PM Michael Koch <[email protected]> wrote:
> Am 28.11.2020 um 14:48 schrieb Paul B Mahol: > > On Sat, Nov 28, 2020 at 2:46 PM Paul B Mahol <[email protected]> wrote: > > > >> > >> On Sat, Nov 28, 2020 at 2:24 PM Michael Koch < > [email protected]> > >> wrote: > >> > >>> Am 28.11.2020 um 13:44 schrieb Paul B Mahol: > >>>> On Sat, Nov 28, 2020 at 1:35 PM Michael Koch < > >>> [email protected]> > >>>> wrote: > >>>> > >>>>> Am 28.11.2020 um 12:57 schrieb Paul B Mahol: > >>>>>> On Sat, Nov 28, 2020 at 12:41 PM Michael Koch < > >>>>> [email protected]> > >>>>>> wrote: > >>>>>> > >>>>>>> Am 27.11.2020 um 20:50 schrieb Paul B Mahol: > >>>>>>>> On Fri, Nov 27, 2020 at 8:24 PM Michael Koch < > >>>>>>> [email protected]> > >>>>>>>> wrote: > >>>>>>>> > >>>>>>>>> Am 27.11.2020 um 19:25 schrieb Paul B Mahol: > >>>>>>>>>> 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. > >>>>>>>>>>> > >>>>>>>>>> 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. > >>>>>>> I did try to reverse engineer the asubboost filter from its output > >>>>>>> signal. Is the attached sketch correct? > >>>>>>> It seems the "feedback" parameter is unnecessary because it does > >>> exactly > >>>>>>> the same thing as "wet". > >>>>>>> > >>>>>> No, your reasoning is invalid. > >>>>>> > >>>>>> I do not have time to draw graphs or do consulting for free. > >>>>> When you swap the values of "wet" and "feedback", the output does > >>> always > >>>>> remain the same. > >>>>> If you think that I'm wrong, please show an example to prove the > >>> opposite. > >>>> Make sure that you take into account decay parameter, delay buffer is > >>> still > >>>> used. > >>> When you swap the values of "wet" and "feedback", the output does > always > >>> remain the same, regardless which values you use for "dry", "decay" and > >>> "delay". > >>> As can be shown with this example: > >>> > >>> set "A=0.4" > >>> set "B=0.7" > >>> > >>> ffmpeg -f lavfi -i aevalsrc='0.5*gt(t,0.1)':d=1 -lavfi > >>> > asplit[a][b];[b]asubboost=dry=0.3:wet=%A%:decay=0.4:feedback=%B%:delay=50[c],[a][c]join,showwaves=draw=full:s=800x300:r=1 > >>> > >>> -frames 1 -y out1.png > >>> > >>> ffmpeg -f lavfi -i aevalsrc='0.5*gt(t,0.1)':d=1 -lavfi > >>> > asplit[a][b];[b]asubboost=dry=0.3:wet=%B%:decay=0.4:feedback=%A%:delay=50[c],[a][c]join,showwaves=draw=full:s=800x300:r=1 > >>> > >>> -frames 1 -y out2.png > >>> > >>> ffmpeg -i out1.png -i out2.png -lavfi vstack -y out.png > >>> > >>> > >>> Red is input step signal, green is output step response of the > asubboost > >>> filter. In the lower half of the output image the "wet" and "feedback" > >>> values are swapped. > >>> > >> What we said previously about delay buffers and that above command? > >> It was literally less than 24h. > > The previous example was "showfreqs" which has a frequency domain > output. Not suitable for analyzing filters which contain delays. > Now I'm using "showwaves" which has time domain output. That's a > different thing. Of course delay lines can be analyzed in time domain. > > > >> That command can not show you the action of delayed input as it is not > >> designed for it. > > A step signal contains all frequencies and is the best possible source > for analyzing unknown black boxes that may contain delays. You can > replace the input by any other source, but you will never find any > difference in the two outputs. It's a fact, "wet" and "feedback" are > interchangeable. > Nope, you are very mistaken. Try with real audio. > > 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".
