[pulseaudio-discuss] [RFC PATCH 0/3] alsa: Support for only-multichannel devices

David Henningsson david.henningsson at canonical.com
Sun Jul 27 11:02:18 PDT 2014

On 2014-07-26 07:13, Raymond Yau wrote:
>  >
>  > This should allow us to automatically probe devices using the recent
>  > firewire drivers, as well as some USB devices people have been asking
>  > about lately.
>  >
>  > Sorry that it has taken some time since I said I would work on this patch
>  > set, and I've rewritten and rethought it as well a few times. Anyway,
> here's
>  > a proposal.
>  >
>  >  * Exact-channels can be set to false to allow devices to be opened with
>  >    any channel count instead of just the one specified in the channel
> map.
> Do these kind of devices need more than one profile if they have same
> channel Min and channel Max and both are larger than two ?

This seems to be the common case that we're trying to handle here, and 
it will end up with the profiles "off", "generic input" "generic output" 
and "generic output + generic input".

> How can user capture stereo from a FireWire device which only support 6
> channels

With this patch set, PA will setup a default channel map. I e, recording 
stereo will mean recording from the first two channels.

> capture as pulseaudio downmix 6 channels to stereo for playback
> stream?
> Can pulseaudio provide a control to select  stereo capture from first
> Jack, second jack .... ?

You'll need module-remap-source for that.

> The problems are non standard volume control names

The firewire drivers currently don't implement volume controls the 
normal ALSA mixer way.
For some other cards (PCI, USB), you're right that the names are 
sometimes non standard. Please fix that in ALSA. :-)

David Henningsson, Canonical Ltd.

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