[FFmpeg-user] asubboost and asupercut

[Michael Koch]

Am 27.11.2020 um 23:27 schrieb Paul B Mahol:
> On Fri, Nov 27, 2020 at 11:20 PM Michael Koch <astroelectronic at t-online.de>
> wrote:
>
>> Am 27.11.2020 um 22:47 schrieb Paul B Mahol:
>>> On Fri, Nov 27, 2020 at 10:40 PM Michael Koch <
>> astroelectronic at t-online.de>
>>> wrote:
>>>
>>>> Am 27.11.2020 um 20:50 schrieb Paul B Mahol:
>>>>> On Fri, Nov 27, 2020 at 8:24 PM Michael Koch <
>>>> astroelectronic at t-online.de>
>>>>> wrote:
>>>>>
>>>>>> Am 27.11.2020 um 19:25 schrieb Paul B Mahol:
>>>>>>> On Fri, Nov 27, 2020 at 7:09 PM Michael Koch <
>>>>>> astroelectronic at t-online.de>
>>>>>>> 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.
>>>>>> Sorry, I didn't understand it. I think this filter could be explained
>>>>>> much better with a block diagram.
>>>>>>
>>>>>>
>>>>>>>> -- 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 unit of the "slope" option?
>>>>>>
>>>>>>
>>>>> 1 / octave, can be set as dB unit, eg. -20dB, 0dB or 1 is max value.
>>>>>
>>>>> Use mentioned mpv command for the reason, as it displays curve.
>>>> The command does not work on my computer. I did download mpv.exe and run
>>>> the command line. mpv exits immediately, no output, no error message.
>>>> When I run mpv without any options, then a mpv window opens.
>>>>
>>> Make sure you run it inside power shell or cmd.exe and make sure you
>> tried
>>> mpv.com too.
>> Now with mpv.com it works. But the version doesn't yet have the
>> asubboost filter. With other filters it works.
>>
> Download the latest release version of mpv. Also note that asubbost is not
> a simple IIR filter
> and thus it can not really show its response.

That's clear. If the filter has a delay line, then a simple frequency 
response makes no sense.

It would really help if you could draw a block diagram for asubboost. 
That would be much easier to understand than a description with words.

Michael

-- 
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   ASTRO ELECTRONIC   Dipl.-Ing. Michael Koch
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