[wdmaudiodev] Re: supporting MuLaw in WDM audio
- From: "Martin Puryear" <martinpuryear@xxxxxxxxxxx>
- To: <wdmaudiodev@xxxxxxxxxxxxx>
- Date: Thu, 29 Aug 2002 15:45:11 -0700
Two thoughts:
a) (I believe this is in the DDK and the non-PCM white paper) DSound does not
use a device's KS filter unless the filter has a PCM pin factory somewhere on
that filter -- a filter that has only pin factories that have only non-PCM data
ranges would not show up in DSound. If CoolEdit uses DSound then perhaps the
lack of a PCM pin is the issue. However, since CoolEdit does see the device,
butcan't record, that probably isn't the problem.
b) For this reason, I suspect that CoolEdit uses waveIn, but does not use ACM
(or the wave mapper), whereas SndRec32 does. There is no MuLaw conversion in
components underneath wdmaud.drv -- this is all done in ACM. Your driver is
probably doing the right things as far as that goes.
Is there a switch within CoolEdit that indicates to use the wave mapper? This
should do the trick.
-Martin
This posting is provided "AS IS" with no warranties, and confers no rights.
----- Original Message -----
From: Larry Cawley
Sent: Thursday, August 29, 2002 11:35 AM
To: wdmaudiodev@xxxxxxxxxxxxx
Cc: lcawley@xxxxxxxxxxxxx
Subject: [wdmaudiodev] supporting MuLaw in WDM audio
Hello,
I have a simple WDM Audio driver that is managing a piece of hardware
that does NOT produce linear PCM audio data (it's MuLaw encoded). The
driver does a simple conversion between MuLaw and PCM audio and
everything works well.
I wanted to let the Windows kernel components (KMixer, ACM, whatever) do
this conversion for me so I changed the WDM audio driver to present
MuLaw as the native audio format. Now when I use Windows Sound Recorder
it records a MuLaw file. That would be expected since the application
supports MuLaw.
I tried running CoolEdit (which apparently only supports linear PCM) and
it fails to allow me to record now (says the driver does not support the
right format).
Why would Windows NOT do this conversion for me? I was expecting
Windows to see that CoolEdit wants linear PCM and the driver only
supports MuLaw and to do the conversion for me. Is there something I
have to do from the WDM driver's perspective to get this to happen ?
Thanks in advance for your help.
---
Larry Cawley
CreativeMedia Software Solutions, Inc.
www.CreativeMediaSoftware.com <http://www.creativemediasoftware.com/>
lcawley@xxxxxxxxxxxxxxxxxxxxxxxxx
(636) 458 1462
Yahoo! IM: lcawley
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