[FFmpeg-user] ffmpeg compand knobs problem

Oliver Fromme oliver at fromme.com
Sat May 17 11:59:18 CEST 2014

Beeblebrox wrote:
 > Is ffmpeg affected by microphone input settings in mixer (oss)?


 > Does ffmpeg use the sound card for any of the processing?


 > Where does the static input come from?

This might be a red herring, but who knows ...  In the past
when I got very high static (white noise) from an audio
conversion, it was usually caused by a byte order problem.
That is, somewhere along the conversion chain, low and high
bytes of the audio samples' were swapped, creating white
noise.  This often happens when handling "raw" audio data.

If you're using sox, take a look at its -x, -L and -B options.

I don't know if ffmpeg provides similar options (I don't think
so).  On the other hand, ffmpeg doesn't read or write "raw"
audio data, so the problem shouldn't occur normally, except
when there's a bug somewhere, i.e. when a decoder or encoder
does not get the byte order right.

Therefore, if your problem is really caused by the wrong byte
order, it's important to debug it and find the bug.

(Of course, the problem might be caused by something entirely
different.  I've never used libfdk_aac before, I don't even
have it installed, so I can't say anything about it.  My audio
is almost always AC3, MPEG1-L3, WAV or raw.)

Best regards


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