[AG-DEV] Re: [AG-TECH]too much Bitrate in RAT

[Robert Putnam]

Reading recently about RAT crashes under MS Windows, I am reminded that
when I was developing my positional audio / window highlighting code, RAT
would routinely crash.  The error message often looked like this:

  Unhandled exception at 0x00430e5f in ratmedia.exe: 0xC0000005: Access
  violation reading location 0x00000018.

I was able to track down what appeared to me to be a race condition whereby
the waveInProc Windows callback could try to access a data structure that
already been freed in w32sk_audio_read.  Since fixing the bug [knock on
wood], I have not seen RAT crash in this way.  

I don't know if other people's RAT crashes have the same cause, since I
only saw it when 3D audio was enabled.  At any rate, I'd like to make the
fix available to the community.  Source is here:  

  http://scv.bu.edu/~putnam/ag-audio/source-2.4/ag-media-positional/rat/auddev_win32.c

And an AG 2.4 AudioService with the fix is here:

  http://scv.bu.edu/~putnam/ag-audio/ratfix-2.4-windows/AudioService.zip


Robert Putnam
putnam at bu.edu
617-353-8295

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   Hi,

   Note that to be compatible with InSORS IGAudio, I think we are restricted to L16-16K-MONO (256kbps), PCMU-16K-MONO (128kbps) and PCMU-8K-MONO (64kpbs).  Of the PCMU codecs, the 16K Mono one should be of the same quality as L16.

   This depends on how important this interoperability is in your meetings - presumably if there was a move to another codec in general, I would guess that InSORS would consider implementing this in IGAudio too, but I wouldn't like to speak for them on this.

   Andrew :)

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   > -----Original Message-----
   > From: owner-ag-tech at mcs.anl.gov [mailto:owner-ag-tech at mcs.anl.gov] On
   > Behalf Of Colin Perkins
   > Sent: 20 July 2006 18:54
   > To: John Hodrien
   > Cc: ag-tech
   > Subject: Re: [AG-TECH]too much Bitrate in RAT
   > 
   > On 20 Jul 2006, at 17:05, John Hodrien wrote:
   > > On Thu, 20 Jul 2006, Robert Olson wrote:
   > >> It may be historical. When we started out the compressed codecs
   > >> seemed to be much less stable.
   > >
   > > I'm not sure that's not still the case.  We had no end of problem
   > > using GSM
   > > under windows with rat crashing.
   > >
   > > There's also the other bonus.  If you compress, you always
   > > introduce a 1 frame delay to the audio.
   > 
   > The way rat works, you always get that delay, no matter what codec is
   > selected.
   > 
   > Colin
   >