problems with mono audio.

problems with mono audio.

[James Courtier-Dutton]

Which devices can a mono stream be played on?
It seems that the only device a mono stream can be played on is the 
"default" pcm device.

Devices like "front" and "rear" are stereo only devices.
It would be nice if alsa-lib would open one of these devices, and if the 
application tries to set 1 channel instead of 2, then somehow make 
alsa-lib do the duplication of the channels.

A similar thing should happen for "surround40" device. If 1 channel is 
asked for, alsa-lib should duplicate it for all channels. If 2 channels 
are asked for, then alsa-lib should create 4 channels automatically.

alsa-lib seems to manage to do this sort of thing for sample rates, and 
sample formats, why not number of channels ?

Cheers
James


-------------------------------------------------------
This SF.Net email is sponsored by: IBM Linux Tutorials
Free Linux tutorial presented by Daniel Robbins, President and CEO of
GenToo technologies. Learn everything from fundamentals to system
administration.http://ads.osdn.com/?ad_id=1470&alloc_id=3638&op=click

Re: problems with mono audio.

[Jaroslav Kysela]

On Thu, 11 Mar 2004, James Courtier-Dutton wrote:

> Which devices can a mono stream be played on?
> It seems that the only device a mono stream can be played on is the 
> "default" pcm device.
> 
> Devices like "front" and "rear" are stereo only devices.
> It would be nice if alsa-lib would open one of these devices, and if the 
> application tries to set 1 channel instead of 2, then somehow make 
> alsa-lib do the duplication of the channels.
> 
> A similar thing should happen for "surround40" device. If 1 channel is 
> asked for, alsa-lib should duplicate it for all channels. If 2 channels 
> are asked for, then alsa-lib should create 4 channels automatically.
> 
> alsa-lib seems to manage to do this sort of thing for sample rates, and 
> sample formats, why not number of channels ?

Have you tried 'plug:front' combination ;-)

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


-------------------------------------------------------
This SF.Net email is sponsored by: IBM Linux Tutorials
Free Linux tutorial presented by Daniel Robbins, President and CEO of
GenToo technologies. Learn everything from fundamentals to system
administration.http://ads.osdn.com/?ad_id=1470&alloc_id=3638&op=click

Re: problems with mono audio.

[James Courtier-Dutton]

Jaroslav Kysela wrote:
> On Thu, 11 Mar 2004, James Courtier-Dutton wrote:
> 
> 
>>Which devices can a mono stream be played on?
>>It seems that the only device a mono stream can be played on is the 
>>"default" pcm device.
>>
>>Devices like "front" and "rear" are stereo only devices.
>>It would be nice if alsa-lib would open one of these devices, and if the 
>>application tries to set 1 channel instead of 2, then somehow make 
>>alsa-lib do the duplication of the channels.
>>
>>A similar thing should happen for "surround40" device. If 1 channel is 
>>asked for, alsa-lib should duplicate it for all channels. If 2 channels 
>>are asked for, then alsa-lib should create 4 channels automatically.
>>
>>alsa-lib seems to manage to do this sort of thing for sample rates, and 
>>sample formats, why not number of channels ?
> 
> 
> Have you tried 'plug:front' combination ;-)
> 
> 						Jaroslav
> 
Yes, I tried all sorts of combinations.
When I play a mono stream to the "front" or "rear" device I get no sound 
at all, but the hw_params for 1 channel is accepted, so my application 
thinks it should work.
This has been tested with aplay.
The sample file used was recorded with the command: -
arecord -fS16_LE -c1 -r48000 test1.wav
and played back with: -
aplay -Dfront test1.wav
Playing WAVE 'test1.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Mono

Cheers
James


-------------------------------------------------------
This SF.Net email is sponsored by: IBM Linux Tutorials
Free Linux tutorial presented by Daniel Robbins, President and CEO of
GenToo technologies. Learn everything from fundamentals to system
administration.http://ads.osdn.com/?ad_id=1470&alloc_id=3638&op=click