[alsa-devel] [PATCH 1/2] Remove definition for surround sound devices on ICE1712.

[Alan Horstmann]

On Wednesday 21 January 2009 10:00, Takashi Iwai wrote:
> At Tue, 20 Jan 2009 17:33:24 +0100,
>
> Diego E. 'Flameeyes' Pettenò wrote:
> > Jaroslav Kysela <perex at perex.cz> writes:
> > > Note that front and surround devices does not support automatic sample
> > > conversion. Use plug:front, plug:surround40 etc. devices.
> >
> > Using the correct format, front:IDX should work with two channels sound
> > files, and it doesn't, nor surround40:IDX works with four channels or
> > surround71:IDX with eight channels.
> >
> > [I'm using IDX because I have it on :1 rather than :0]
>
> I thought plug:front:IDX works, at least on 1.0.19, too...

It does work here on older Alsa.

I think Diego's point though is that 'surround40:IDX' might be expected to be 
a 4-channel stream, whereas it is as dependant on the hardware as 'hw:IDX' 
is.  In the later case it is clear that the user must provide audio in 
whatever format/channels the hardware uses.  However it is unexpected that eg 
on ice1712 'surround40:IDX' requires a 10-channel playback stream and ignores 
6 of them, and will not play a 4-channel stream.

It is also not symetrical, so if you capture it has to be a 12-channel stream, 
which it is then not possible to play without using the plug: devices.

Unless I am mistaken...

Alan