[alsa-devel] Selecting correct input device port.

[Takashi Iwai]

At Tue, 28 Oct 2014 09:57:18 +0530,
dE wrote:
> 
> As I learn't in this mailng list, a device can typically handle only one 
> stream at a time unless it supports hardware mixing which's exposed via 
> subdevices in ALSA
> 
> What does subdevice mean for input device?

When a device can do multiplexing, the driver can give multiple
substreams (= subdevices).

> Do they mark physical ports 
> for input? If not how do I record from a specific input port?

You can pass the subdevice number explicity.  It's -1 as default,
which means to select the next free one.

> Is it 
> automatically selected by the card?
> 
> And what's 'input source' in ALSA mixer?

It's usually a MUX to select the input source, e.g. line in or mic.


Takashi