[FFmpeg-user] Dithering in 'aresample' has no effect

[林至善]

Hi all,

I am trying to compare the wav file with/without dithering, but it seems
that my command doesn't work. Here's my command line and console output:

[1] *ffmpeg -i Fsweep96.wav -af
aresample=8000:dither_scale=0:dither_method=0 Fsweep8_NoDither.wav* (I
would assume this would generate a file *without *dither,
Fsweep8_NoDither.wav)
[image: 1.JPG]

[2]* ffmpeg -i Fsweep96.wav -af
aresample=8000:dither_scale=1:dither_method=rectangular Fsweep8_Dither.wav *(I
would assume this would generate a file *with *dither, Fsweep8_Dither.wav)
[image: 2.JPG]

But the output file Fsweep8_NoDither.wav/Fsweep8_Dither.wav are totally the
same, both the wav header and the PCM value(it should be
increased/decreased by a small value like +-1 in Fsweep8_Dither.wav).

The question is :
*It seems that my command doesn't work. Is that correct? If I want to
enable/disable dithering, what command should I use?
*Command line mentioned above uses the default resampler, 'swr'. Can I
enable/disable dithering when using resampler 'soxr'?

Thanks a lot for any help!


LCS

[Michael Niedermayer]

Post by 林至善
Hi all,
I am trying to compare the wav file with/without dithering, but it seems
[1] *ffmpeg -i Fsweep96.wav -af
aresample=8000:dither_scale=0:dither_method=0 Fsweep8_NoDither.wav* (I
would assume this would generate a file *without *dither,
Fsweep8_NoDither.wav)
[image: 1.JPG]
[2]* ffmpeg -i Fsweep96.wav -af
aresample=8000:dither_scale=1:dither_method=rectangular Fsweep8_Dither.wav *(I
would assume this would generate a file *with *dither, Fsweep8_Dither.wav)
[image: 2.JPG]
But the output file Fsweep8_NoDither.wav/Fsweep8_Dither.wav are totally the
same, both the wav header and the PCM value(it should be
increased/decreased by a small value like +-1 in Fsweep8_Dither.wav).
*It seems that my command doesn't work. Is that correct? If I want to
enable/disable dithering, what command should I use?

try choosing a more precisse internal sample format, for example:
"-internal_sample_fmt fltp"

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