[FFmpeg-user] Sometimes a lot of noise

Belcampo belcampo at zonnet.nl
Wed May 30 11:12:41 CEST 2012

On May 30, 2012, at 12:52 AM, Cecil Westerhof wrote:

> Op dinsdag 29 mei 2012 11:37 CEST schreef belcampo at zonnet.nl:
>>> To record audio I use the following command:
>>> ffmpeg -y \
>>> -f oss \
>>> -i /dev/dsp \
>>> -ac 1 \
>>> -ar 22050 \
>>> -ab 64k \
>>> dummy.ogg
>>> The strange thing is that most of the time I have a good recording,
>>> but sometimes the audio is faint and with a lot of white noise. (And
>>> because of Murphy, this happens when I record a long audio.) Anybody
>>> an idea why this happens? And what to do about it?
>> Could it be that the 'white noise' problem hits you when the source is dolby
>> 	or dts and there is no dolby/dts-decoder available in your ffmpeg version
>> 	? Just a guess.
> I do not think so. It is also the same source: a microphone. For
> example: Monday I recorded something. The sound was faint, with a lot
> of noise. I immediately made a new recording. (With the same
> microphone. I removed it and put it back, but that should make no
> difference, or should it?) That recording was correct again. So then
> it should not be this problem I think.
No if the source is the same, your microphone, it has to something else.
Your microphone is the same, your ffmpeg version is the same, your command line is the same. The difference is removing and reinserting your microphone.
Is it a 'real' microphone, connected with a 3.5' jack, or the microphone of a webcam connected with USB ?
If it's a 3.5' jack it looks like some alsa/pulse problem or it could be some USB/IRQ problem. Does the log tell something when you remove and reinsert the microphone ?
> -- 
> Cecil Westerhof
> Senior Software Engineer
> LinkedIn: http://www.linkedin.com/in/cecilwesterhof
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