[alsa-devel] What are subdevices?

[dE]

On 10/26/14 15:27, dE wrote:
> On 10/26/14 14:41, Clemens Ladisch wrote:
>> dE wrote:
>>> A device seems like the output streams the sound card supports. Like 
>>> HDMI, DP, analog etc...
>>>
>>> So what's a subdevice?
>> A subdevice is an output streams the sound card supports.
>>
>> Typically, a device has multiple subdevices if the card supports 
>> hardware mixing; all
>> the subdevices end up at the same physical output.
>>
>>
>> Regards,
>> Clemens
>
> Ok, so a device list is a list of different streams the card can 
> supports simultaneously and they'll be output via different channels 
> without mixing.
>
> Thanks for clarifying this.
>
> But, typically cards have a single analog device but support 
> multichannel output. So how does this work at the software level? If 
> ALSA can't send multiple streams of audio to one device, then how does 
> ALSA send  separate output to different channels of the device?
>
> Is the PCM sent to the sound card codified? Is this the same way how 
> stereo work?

No one knows?