Sound stuff

John M McIntosh johnmci at smalltalkconsulting.com
Wed May 16 17:42:05 UTC 2007


On May 16, 2007, at 9:59 AM, Brian Brown wrote:

> Which also plays back much faster than the recording should. Anyone  
> have any ideas why there would be this mismatch?

would that be the issue below?


> 	From: 	  yoshiki at squeakland.org
> 	Subject: 	Sound Recording on Mac
> 	Date: 	November 8, 2006 6:00:46 PM PST (CA)
> 	To: 	  johnmci at smalltalkconsulting.com, squeak- 
> dev at lists.squeakfoundation.org, etoys at laptop.org
>
>   Hello,
>
>   Has anybody tried sound recording and playback on Mac lately?  Scott
> reported that it is broken in Squeak 3.9 7067 (and OLPC etoys image)
> on 3.8.12beta4U.app VM.  What happens is that if you record your voice
> with a SoundRecorderMorph or EventRecorderMorph (with the voiceControl
> enabled) and play the recorded sound back, you get incorrect sound.
>
>   Here is what Scott described:
>
> --------------------------------------
> (a)  The sound-in-event-recorder bug *does* occur [in 3.9 7067].   
> But it's slightly
> different:  although the speed of playback is nearly doubled, as in
> OLPC, the *pitch* does not change.  So it is not a Donald Duck sound.
>
> (b)  Also, the same bug now (i.e. in 3.9) also occurs in the vanilla
> SoundRecorderMorph!  (In the OLPC/Mac image, the vanilla
> SoundRecorderMorph produces good playback on the Mac -- it's only the
> use of sound within an EventRecorderMorph that's problematical.  In
> the 3.9/Mac image *every* SoundRecorderMorph use has this problem.
> But again, the overly-fast playback occurs *without* a pitch rise.)
>
> So evidently 3.9 went "final" with the SoundRecorder completely
> broken on the Mac.
> --------------------------------------


> 	From: 	  dominiqued at versateladsl.be
> 	Subject: 	Re: SoundRecorder
> 	Date: 	November 26, 2006 3:46:21 AM PST (CA)
> 	To: 	  squeak-dev at lists.squeakfoundation.org
> 	Reply-To: 	  squeak-dev at lists.squeakfoundation.org
>
> 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.
>

--
======================================================================== 
===
John M. McIntosh <johnmci at smalltalkconsulting.com>
Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
======================================================================== 
===





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