Filter inputs will be auto-converted from any non-float formats to
float or double one. Float/double formats are in [-1 .. +1] interval.
Thank you very much for the amultiply filter, it works great!
Here is an example for an ultrasonic converter which downconverts the
15kHz - 25kHz band to the 0 - 10kHz band.
First make an input file for testing. This is a 2 second 19kHz tone
followed by 2 seconds silence:
c://ffmpeg/ffmpeg -f lavfi -i
"sine=frequency=19000:sample_rate=48000:duration=2" -af apad -t 4
ultrasonic.wav
Then use the downconverter:
c://ffmpeg/ffmpeg -i ultrasonic.wav -f lavfi -i
"sine=frequency=15000:sample_rate=48000" -filter_complex
"[0]highpass=f=15000,highpass=f=15000,highpass=f=15000,highpass=f=15000[sound];[1]volume=8[sine];[sound][sine]amultiply[mixed];[mixed]lowpass=f=10000,lowpass=f=10000,lowpass=f=10000,lowpass=f=10000"
out.wav
Michael
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