[FFmpeg-user] Sometimes a lot of noise

Cecil Westerhof Cecil at decebal.nl
Sun Jun 3 19:57:01 CEST 2012

Op woensdag 30 mei 2012 11:12 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 ?

Yes, it is a real microphone: Microphone Starzz Trust.

I did not look at the log. Next time it happens I'll keep an eye on
the log.

Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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