[wdmaudiodev] Re: Question about APO and multichannel inputs

  • From: Larry Osterman <Larry.Osterman@xxxxxxxxxxxxx>
  • To: "wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Tue, 11 Aug 2009 04:46:21 +0000

Note that your IsInputFormatSupported call won't always be made in audiodg.exe, 
sometimes it will be made in the audio service itself.

From: wdmaudiodev-bounce@xxxxxxxxxxxxx 
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of 
Sent: Monday, August 03, 2009 9:54 AM
To: wdmaudiodev@xxxxxxxxxxxxx
Cc: wdmaudiodev@xxxxxxxxxxxxx; wdmaudiodev-bounce@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: Question about APO and multichannel inputs

I am faced with a similar problem with an LFX APO we have.
Why is the behavior different for different players and how do we use the API 
IsInputFormatSupported() and IsOutputFormatSupported() correctly, so we can do 
the right thing?
Any code snippets?


Arunasree Swapna
Software Engineer
360-514-5760 (office)
[Inactive hide details for "Cheng-mean Liu (SOCCER)" 
<soccerl@xxxxxxxxxxxxx>]"Cheng-mean Liu (SOCCER)" <soccerl@xxxxxxxxxxxxx>

"Cheng-mean Liu (SOCCER)" <soccerl@xxxxxxxxxxxxx>

Sent by: wdmaudiodev-bounce@xxxxxxxxxxxxx

08/03/2009 09:47 AM
Please respond to


"wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>



[wdmaudiodev] Re: Question about APO and multichannel inputs

When running with different players, are you seeing different behavior (call 
parameters, return code) in your APO's handling of IsInputFormatSupported()?

From: wdmaudiodev-bounce@xxxxxxxxxxxxx 
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of MikeLee@xxxxxxxxxxxxxx
Sent: Monday, August 03, 2009 5:46 AM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Question about APO and multichannel inputs

Hi All,

I am developing a LFX APO to implement a stereo headphone with surround effect. 
The APO includes a multi-channel to stereo virtualizer. The APO can accept both 
stereo input and multi-channel input and output stereo virtualized sound. Now, 
we are testing our APO. If the test player is Windows Media player, the APO 
works fine. We can try a 2-channel songs and then a 6-channel music. The APO 
input channel number is changing with the file content which is playing by WMP.

But, it is not the case of other players. When we use WinAmp as player and play 
a stereo music file and then drag a 6 channel file to play. The result is we 
can not see any format change action in APO side. And the input format remain 
unchanged 2 channel. The 6 channel file is down mixed to 2-channel to be 
received by APO. Since APO did not get the exact multi-channel data, the 
virtualized result is not what we desired.

I tried another player; it has the same behaviors as WinAmp.

Does any one know why it happens?

Why WMP can void this problem?

I am trying to fix the input format to 6-channel( by change 
IsInputFormatSupported() and IsOutputFormatSupported() ), but failed. Is it 

Thanks in advance.

Software Dept.
VIA Technologies (China) Inc., Ltd.
E-mail: MikeLee@xxxxxxxxxxxxxx
Tele: 86-010-59852288 ext.3830

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