[wdmaudiodev] Re: Msvad pcmex, audio channel mask

  • From: Kim Therkelsen <kim_t26@xxxxxxxxxxx>
  • To: "wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Mon, 4 Feb 2013 19:41:01 +0000

> What if the stereo stream started first? In my case it could be okay to 
> always receive 8 channels as long as some meta-information tells the audio 
> driver which of the channels are in use, for instance stereo signals would 
> only fill data in the left and right front channels. In the case where the 
> stereo stream started before the 7.1 stream, the meta-information should 
> change/update when the 7.1 stream starts so that the driver knows all the 
> channels are in use. There are probably many pitfalls I don't know about and 
> probably some very good reasons it works the way it does today. The things I 
> have read about the pre-mix render sAPO, LFX, makes me think that it is the 
> solution i need. 
> http://msdn.microsoft.com/en-us/library/windows/desktop/dd370876(v=vs.85).aspxOn
>  the linked page it says: "For example, a particular LFX APO might accept a 
> 6-channel surround sound stream from a client and convert the stream to a 
> stereo format that can be played through headphones."
That is what i want to do, I always need to downmix the audio signals to two 
channels. I will look some more at the "Custom Audio Effects in Windows Vista" 
document.Is the LFX the way to go?Is it the only way to get to perform the 
downmixes myself? Is there any way I can install an LFX APO without bundling it 
with an audio driver? Ideally I just want to add my own LFX to the existing 
audio drivers in the system. Regards/Kim From: Matthew.van.Eerde@xxxxxxxxxxxxx
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: Msvad pcmex, audio channel mask
Date: Mon, 4 Feb 2013 16:58:08 +0000









> in that case it should default to the highest common number of channels, 8.
 
What if the stereo stream started first?
 


From: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx]
On Behalf Of Kim Therkelsen

Sent: Monday, February 4, 2013 2:29 AM

To: wdmaudiodev@xxxxxxxxxxxxx

Subject: [wdmaudiodev] Re: Msvad pcmex, audio channel mask


 

Hi Rob,



Thank you for the answer. I was afraid of that. It is important for me to 
perform the downmix myself. Is there a way to accomplish this by for instance 
making a LFX instead?



I also find the behaviour suboptimal in some cases. An example of this is when 
connecting a PC to a surround receiver using HDMI, in that case you would want 
the surround receiver to decide if an upmix should be performed and perform it 
if needed. Ideally it
 should know if the audio material is stereo or true 7.1 surround material. 
Even though Windows would not upmix the stereo content to 7.1, the surround 
receiver would not know this as it receives 8 channels (6 containing silence). 
I realize that it becomes
 a problem when playing back multiple audio tracks (both stereo and 7.1) at the 
same time on a PC but in that case it should default to the highest common 
number of channels, 8.



Regards,

/Kim

                                          

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