[Pkg-alsa-devel] Bug#305189: gstreamer0.8-alsa: ALSA plugin isn't working
lool at dooz.org
Thu Nov 29 20:51:01 UTC 2007
reassign 305189 libasound2
retitle 305189 [VIA 8237 with ALC850] doesn't offer a working "default"
On Tue, May 10, 2005, Anders Boström wrote:
> But why isn't alsasink working with the default alsa configuration?
> All other alsa applications I've tested work fine with the default
This is an ALSA bug, there are ways to work around it -- which other
applications do -- but it's best to solve it at the ALSA level.
The following gets technical.
The ALSA API is split in a number of sub-APIs, the problematic API here
is the PCM API which is available at:
From a discussion with GStreamer maintainers, a first class of problems
concerns this API and seems to be the following:
- ALSA offers application writers some guarantee that a special ALSA
device named "default" exists and works
- sometimes, I presume for some ALSA modules / drivers, the "default"
devices either doesn't exists or doesn't work
- a workaround is to try the ALSA device named "hw:0" (which refers to
the first sound card), this is ugly as ALSA is always offering a
"default" which should be used; GStreamer folks don't want to
implement that workaround in the alsasink plugin, but you saw it is
possible to force the ALSA device yourself as an alsasink parameter
- another workaround is to change the user or system configuration so
that "default" is "hw:0", this is what the .asoundrc snipset I gave
From the same discussion with GStreamer maintainers, a second class of
problems appears with respect to a second API, the control API which is
In this case, the problem seems to be the following (you're not
experiencing this problem):
- ALSA offers application writers a mean of retrieving information on a
- GStreamer can adapt an input stream to a set of output capabilities
if necessary, but if for example the PCM device seems to accept
anything, GStreamer doesn't adapt the stream
- in some cases, I presume for some modules / drivers, ALSA reports
that the PCM device supports all kinf od streams while it doesn't,
and this leads to a failure
- a workaround is to try to change the format after failure, but
GStreamer folks don't want to do this
I'm reassigning this bug to libasound2, the ALSA library. I hope
information about your hardware will be enough to diagnose this problem
Loïc Minier <lool at dooz.org>
"Neutral President: I have no strong feelings one way or the other."
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