[mythtv-users] No Alsa output without OSS emulation?

Michael T. Dean mtdean at thirdcontact.com
Fri Jun 30 13:14:16 UTC 2006

On 06/29/2006 10:00 PM, Sage wrote:
> On 6/29/06, Michael T. Dean <mtdean at thirdcontact.com> wrote:
>> On 06/29/2006 07:24 PM, Sage wrote:
>>> I'm running MythTV 0.19-fixed, compiled from source, on Ubuntu 6.06
>>> (Dapper Drake).  Despite the fact that I compiled MythTV with OSS
>>> support disabled, I am unable to hear sound without the alsa-oss
>>> emulation package installed.
>> http://www.gossamer-threads.com/lists/mythtv/users/185108#185108
>> (whole message including quoted material--applies to more than just
>> transcoding, BTW, including recording on some hardware)
>> Or, for the short version:
>> http://www.gossamer-threads.com/lists/mythtv/users/185111#185111
>>> Is this a requirement of MythTV?  In the general settings, I have set
>>> ALSA:default as my playback device, and I have a working .asoundrc,
>>> and I disabled OSS support in MythTV before I compiled it.  Sound
>>> didn't work until I installed the alsa-oss package (all other alsa
>>> packages were already installed).  Why do I need OSS installed in
>>> order to play sound?
>> You don't (and I would /never/ install OSS on /any/ system).  You just
>> need OSS emulation support.
>>>   Has anyone else run into this problem before?
>> Search the archives for "disable-audio-oss" (no quotes) and you'll see
>> all the other people who tried to make a "cleaner" system by "not
>> installing" OSS.
> Thanks for the response.  So to clarify:
> 1. Even if ALSA is installed, MythTV does not work without OSS
> emulation, and this is normal.

Myth uses OSS calls for recording audio (or writing audio in transcodes 
or ...).  Native ALSA can be used /only/ for playback.

> 2. --disable-oss should *only* be used on systems that do not have OSS
> or OSS emulation available, such as Mac OS X, because it cripples
> MythTV's functionality in ways the user may not expect.
> Correct?

Exactly.  Some will tell you that it's OK to disable it on frontend 
systems, but you're on your own if you do so (it's not a supported 
configuration).  As Isaac said, "What's the big deal about keeping 
alsa's oss emulation turned on? It doesn't hurt _anything_." ( 
http://www.gossamer-threads.com/lists/mythtv/users/128478#128478 )  And, 
a frontend system that was compiled with "--disable-audio-oss" cannot do 
certain jobs for you, so if you ever decide to let your frontend help 
with transcodes, you'd have to recompile.  A better approach is to 
compile with OSS support and if it really bugs you, don't load the ALSA 
OSS modules.  Then, if you later need them, you can just load them.

Note, also, that using "--disable-audio-oss" doesn't "make a cleaner 
system that doesn't require installing OSS", it just tells Myth to 
compile only the parts that don't rely on calls that use the OSS API.  
Unless you really care to determine--every time you compile 
MythTV--whether those parts are required for your particular system, you 
should just /never/ specify "--disable-audio-oss".

And, using "--disable-backend" and "--disable-frontend" are also not 
supported on GNU/Linux systems...


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