[gst-devel] [oss-devel] [Correction] libgstoss4audio / SNDCTL_MIX_READ

Tim Müller t.i.m at zen.co.uk
Thu May 8 21:35:15 CEST 2008

On Thu, 2008-05-08 at 14:14 +0100, Clive Wright wrote:

Hi Clive,

> The recently added gstreamer plugin for OSS4 has problems handling the
> value returned by SNDCTL_MIX_READ for control type MIXT_MONOSLIDER16
> (and I suspect MIXT_MONOSLIDER).
> See attached extract of oss4_mixer.log
> This appears to be caused by stereo values being returned by
> SNDCTL_MIX_READ for these control types.

Yes, you're right. I've seen this too.

> The OSS v4 Programmer's guide is not explicit in this situation (...)
> Perhaps this should be filed as a bug report but I am mindful of getting
> into the not uncommon situation where two projects claim that it is the
> other projects responsibility.

Well, in general we prefer patches to be submitted via bugzilla [0]. I
like to think most of us are reasonable people most of the time and
can't really remember too many occasions where inter-project
blame-gaming led to a bug left unfixed.

In any case, I don't know if this is intentional on OSS's part or not
(it seems not though, since at least ossmix writes values as single
values instead of mirroring the single mono value in the upper bits),
but I don't see why we shouldn't work around it.

> A quick fix in the form of a patch for gstreamer-plugins-bad is attached.

This is ok in principle, only that the volume[1] might cause bad memory
access for mono sliders, since the caller will only pass in an array
with space for one channel.

I've committed a slightly modified version. I hope it works. If not,
please open a bug in bugzilla, thanks!


[0] http://gstreamer.freedesktop.org/wiki/SubmittingPatches

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