Bug 29854

Summary:	Add some info regarding oss-emulation bug
Product:	[OLD] Docs-user	Reporter:	Fernando Serboncini (RETIRED) <fserb>
Component:	Alsa Configuration Guide	Assignee:	Sven Vermeulen (RETIRED) <swift>
Status:	RESOLVED FIXED
Severity:	minor	CC:	docs-team
Priority:	High
Version:	unspecified
Hardware:	All
OS:	Linux
Whiteboard:
Package list:		Runtime testing required:	---
Attachments:	Patch to fix oss emulation issues (including note to add "oss" to USE) New patch to please BennyC :-)

Description Fernando Serboncini (RETIRED) gentoo-dev

2003-09-28 19:09:59 UTC

I've found some info when installing ALSA in my Gentoo that may be usefull for
the ALSA Guide:
 
when I first installed the default portage ALSA (I guess it's 0.9.2), OSS
emulation was really noisy altought pure alsa aplications did work fine. I've
tried installing the 0.9.6 version but the problem remained.
 
After a few hours of google search, i've found the problem... there is a feature
in ALSA that makes OSS Emulation use /dev/dsp with alsa's 4-channel output and
/dev/adsp with the normal output but this stuff is kinda broken for some cards.
 
The workaround is to tell alsa oss emulation to flip those, by adding:
"options snd-pcm-oss dsp_map=1" to /etc/modules.d/alsa
 (actually you're saying that /dev/dsp is the 2nd alsa output)
 
In my case the bug could also be corrected by changing a set in my card:
"options snd-via82xx enable=1 dxs_support=0" in /etc/modules.d/alsa
 
just for records, I own a A7V8X-X motherboard, onboard sound card.
 
Anyway, I think it would be useful for people installing ALSA knowing 
that this stuff may happen.
 
IMHO, I think a chapter should be added in the Final Notes about it.
Specially to warn people that they should test ALSA with pure alsa software, and
only after this moving to oss-emulated stuff.

Reproducible: Always
Steps to Reproduce:
1. Installing ALSA drivers
2. Using ESD over OSS-Emulation


Actual Results:  
The output sound is noisy.

Comment 1 Sven Vermeulen (RETIRED) gentoo-dev

2003-10-04 09:58:02 UTC

Created attachment 18749 [details, diff]
Patch to fix oss emulation issues (including note to add "oss" to USE)

Comment 2 Benny Chuang (RETIRED) gentoo-dev

2003-10-05 05:05:22 UTC

but you'll have to define
+<e>oss</e> in your USE-variable too.

how about "only if you define <e>oss</c> in your USE-variable."?

the rest looks good

Comment 3 Fernando Serboncini (RETIRED) gentoo-dev

2003-10-05 08:44:05 UTC

perfect to me.

Comment 4 Sven Vermeulen (RETIRED) gentoo-dev

2003-10-05 11:33:04 UTC

Created attachment 18795 [details, diff]
New patch to please BennyC :-)

Comment 5 Benny Chuang (RETIRED) gentoo-dev

2003-10-07 15:07:52 UTC

patch looks good :D

Comment 6 Sven Vermeulen (RETIRED) gentoo-dev

2003-10-09 02:00:23 UTC

committed