[FFmpeg-user] Frequency response of an ffmpeg equalizer filter

[Nicolas VAMBAIRGUE]

Le 26/06/2020 à 18:15, Paul B Mahol a écrit :
> On 6/26/20, Nicolas VAMBAIRGUE <nicolas2020 at nv76.info> wrote:
>> Hello,
>>
>>
>> I'm starting to use the ffmpeg filters, using the documentation. It
>> seems working but, I don't find the way to get the frequency response of
>> a filter. For example, let's say I'm applying this filter :
>>
>> equalizer=f=7000:t=q:w=2:g=2,equalizer=f=1000:t=q:w=1:g=3,equalizer=f=80:t=q:w=2:g=-30
>>
>> in the following command :
>>
>> ffmpeg -re -i /home/dr_click/live.wav -acodec pcm_s16be -ar 44100 -ac 2
>> -f rtp -af
>> "equalizer=f=7000:t=q:w=2:g=2,equalizer=f=1000:t=q:w=1:g=3,equalizer=f=80:t=q:w=2:g=-30"
>> rtp://127.0.0.1:1234
>>
>> It works, I'm hearing a distorted sound. And what I'd like to know, with
>> such a filter, is the db gain for the 2000 Hz signal or for the 150Hz
>> signal or any other frequency with a query like : give me your frequency
>> and I'll tell you which gain is applied at this frequency with the
>> defined filter.
> Yes, with anequalizer filter.

         => Ok, so let's say I'm using this command with an anequaliwer

         =>_ffmpeg -re -i /home/dr_click/live.wav -af "anequalizer=c0 
f=200 w=100 g=-10 t=0|c1 f=200 w=100 g=-10 t=0 curves=true" -acodec 
pcm_s16be -ar 44100 -ac 2 -f rtp rtp://127.0.0.1:1234

         => How do I get the frequency graph of such a filter ? Is it 
mandatory to get a video stream (and how to get / display it) ? Can't I 
get command with the frequency as input and the gain as output ? Of 
course, such a command would means I need to query the db output for 
each interesting frequency.

>
>>
>> Thank you for your help,
>>
>>
>> Nicolas
>>
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