SoundRecorder
Bert Freudenberg
bert at freudenbergs.de
Sun Nov 26 12:25:09 UTC 2006
On Nov 26, 2006, at 12:46 , Dominique Dutoit wrote:
> I think I have found the culprit.
>
> If you listen carefully to the recorded sound, you will notice that
> frames are dropped at regular intervals. Since this pattern is
> quite obvious and the VM doesn't seem to screw the sound data, it
> should be something happening at the image level.
>
> Looking for a clue in a 3.9 alpha version, I found a change made by
> "dgd" on April 4, 2006:
>
> "workaround for OSS emulation on top
> on ALSA (on Linux environments)"
> (Delay forMilliseconds: 20) wait.
>
> If the last line is commented out, the sound recorder just works as
> expected. The same code is present in the OLPC and Squeakland
> images and both work pretty well without this delay.
>
> CoreAudio records the audio input in real time but SoundRecorder
> picks the data once in a while. The end result is that the sound
> data is stored in a different time frame that the sampling rate and
> the sound plays faster.
>
> Now I am not sure what can be done to have a cross-platform
> solution, but as far I have seen the problem is not on the Mac VM
> side.
Since there is now an ALSA plugin we don't really need the OSS
emulation anymore. Maybe Diego could explain what this was about?
- Bert -
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