bug in playing 6-channel sound

bug in playing 6-channel sound

[Julian Bradfield]

Some five years ago, the following post

https://mailman.alsa-project.org/pipermail/alsa-devel/2014-February/072265.html

reported a failure to play six-channel sound, that could be worked
around by setting the prealloc value for the device to various values
*other than* the default 64. 

I have just run into this playing a movie from my laptop (Thinkpad
Yoga X1, Intel HDA PCH sound card outputting through HDMI) running
Xubuntu 18.04, up to date as at the time of posting.

I see exactly the same problem as in that post, and the same
workaround works for me - I tried prealloc values 63,65,32,128, and
any of them is ok.

I'm a bit baffled that such a problem has survived for several years.

If any developer would like me to provide debugging information,
please get in touch - I have some time available at present, but not
enough to learn ALSA and debug it myself!

I will remain subscribed to the list for a few weeks to read any
followups.

Re: bug in playing 6-channel sound

[Takashi Iwai]

On Thu, 04 Jul 2019 12:46:20 +0200,
Julian Bradfield wrote:
> 
> Some five years ago, the following post
> 
> https://mailman.alsa-project.org/pipermail/alsa-devel/2014-February/072265.html
> 
> reported a failure to play six-channel sound, that could be worked
> around by setting the prealloc value for the device to various values
> *other than* the default 64. 
> 
> I have just run into this playing a movie from my laptop (Thinkpad
> Yoga X1, Intel HDA PCH sound card outputting through HDMI) running
> Xubuntu 18.04, up to date as at the time of posting.
> 
> I see exactly the same problem as in that post, and the same
> workaround works for me - I tried prealloc values 63,65,32,128, and
> any of them is ok.
> 
> I'm a bit baffled that such a problem has survived for several years.

Maybe just because most distros use the larger preallocation size via
kconfig option since long time ago.  It's kept to 64 as default in the
source tree just for a historical reason.


Takashi