Am 21.10.2020 um 20:36 schrieb Paul B Mahol:
On Wed, Oct 21, 2020 at 08:14:50PM +0200, Michael Koch wrote:
Hi,
I'm just testing the new afreqshift filter.
In my first test I did use only *.wav audio files. This test was successful.
In my next test I'm using MP4 files. First I make a test video with a 5kHz
tone:
ffmpeg -f lavfi -i sine=f=5000:r=48000:d=5 -f lavfi -i color=black -lavfi
showspectrum=legend=1 -y test.mp4
Now I try to shift the frequency down by 4kHz:
ffmpeg -i test.mp4 -lavfi afreqshift=-4000,showspectrum=legend=1 -y out.mp4
The spectrum display is showing the expected 1kHz, but what I hear is 5kHz.
What's wrong with my command line? Why is the output of the afreqshift
filter not mapped to the output file?
Something like this:
ffmpeg -i test.mp4 -lavfi "asplit=2[a][b],[b]afreqshift=-4000,showspectrum=legend=1[b]" -map
"[a]" -map "[b]" -y out.mp4
You ignored fact that showspectrum is just A->V filter.
That did also not work, the audio output is 5kHz. But thanks for
pointing me in the right direction. The asplit filter must be after the
afreqshift filter. This works:
ffmpeg -i test.mp4 -lavfi
afreqshift=-4000,asplit[a][b];[b]showspectrum=legend=1 -map "[a]" -y
out.mp4
Thanks,
Michael
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