[FFmpeg-user] Multiply audio samples

Michael Koch astroelectronic at t-online.de
Wed Sep 12 11:07:02 EEST 2018

Am 12.09.2018 um 09:55 schrieb Paul B Mahol:
> Hi,
> On 9/12/18, Michael Koch <astroelectronic at t-online.de> wrote:
>> Is it possible to multiply audio samples from two sources?
>> I'd like to downconvert the 15kHz to 25kHz range to the 0 to 10kHz
>> range. First apply a strong 15kHz highpass filter, then multiply the
>> signal with a 15kHz sine wave (which produces sum and difference
>> signals), then apply a 10kHz lowpass filter.
> There is no yet amultiply audio filter, but I could write it.
> Am I correct that for it you need two audio streams as input and one
> audio stream as output?

yes, two inputs and one output. I think it would be best if it works 
independant of bit depth. First normalize the input signals to -1...+1 
range, then multiply them so that the result is also in the -1...+1 
range, then normalize back to 16bit or 24bit range.


   ASTRO ELECTRONIC   Dipl.-Ing. Michael Koch
        Raabestr. 43   37412 Herzberg
   Tel. +49 5521 854265   Fax +49 5521 854266

More information about the ffmpeg-user mailing list