[alsa-devel] [TDM help please] multiplex out a stereo I2S line

[Matt Flax]

On 14/10/16 15:34, Matt Flax wrote:
> Hi there,
>
> Problem is that I need multiplex all 6 channels out a stereo I2S line.
>
> I have a working system ... the CPU thinks it is stereo I2S, but the 
> codec thinks it is TDM multichannel. When I aplay a pre-interleaved 
> wav file, it works ! Check the video here : 
> https://www.kickstarter.com/projects/1250664710/1299781340?token=e465b540
>
> Problem is that I need to multiplex all 6 channels down the stereo I2S 
> line. I have tried to do this with the asoundrc by attempting to 
> declare the same device 3 times and interleaving there, however have 
> failed.
>

Does anyone know if there is a ALSA plugin which allows multiplexing of 
N channels to a single interleaved stream ?
It is simple, it seems to do the opposite and interleave multiple sound 
card streams into one stream... but I can't see how to do the opposite 
... have a virtual sound card of N channels which muxes down to one 
stream on a stereo machine/cpu/codec line.

> I am happy to alter my machine driver to implement this ... Is there a 
> way to present 3 stereo subdevices to the user, where each of these 
> subdevcies is interleaved to form the TDM before sending to the codec ?
>
> Is there perhaps a better or more elegant way to go about this ?
>
> thanks
>
> Matt
>
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