[vorbis] Is GCC 2.95.2 also unusable?

volsung at asu.edu volsung at asu.edu
Sat Oct 13 14:31:25 PDT 2001

On Sat, 13 Oct 2001, Philippe Tapon wrote:

> Does anyone know if GCC 2.95.2 compiles a broken oggenc?  My .ogg files 
> sound like they're being played by a CD player stuck on fast-
> forward. . . . And I wonder what the solution is.  
> Philippe
> (YellowDogLinux 1.2.1 (a Red Hat 6.2 derivative) on an iMac)

Hmm.  I'm going take a wild guess as to what the problem is, since your
symptoms resemble a problem I've seen twice before (stop me if any of this

I think the problem is not with oggenc (the compiler issue you refer to
generates artifacts, but not fast-forward like behavior), but rather with
libao, the library that does audio output for ogg123.  If you are not using
ogg123, then I'm totally wrong.

However, if you are, you would be the third Linux+Mac user to observe this
problem.  It occurs because libao opens the audio device in non-blocking mode
and then turns blocking on after the device is open.  (There are good reasons
for this, which I can explain if you care.)  However, one or more of the audio
drivers for Linux on PPC seem to be ignoring the second call in libao that
turns the blocking flag back on.  This is a bug in the audio driver and not
libao, however.

Please see http://bugs.xiph.org/show_bug.cgi?id=48 for a patch to libao to
work around this problem.  You'll note in my explanation on Bugzilla that I
want to make a configure test to check for this bug, but I don't know how to
test for it, so I haven't yet.  If anyone has some good ideas let me know.

Can you tell me which kernel modules you use for sound?  Also, I would suggest
you contact the maintainer of the sound drivers you are using, explain your
problem and point them at the bug page I listed above.  You can also give them
my email address if they need a more detailed description of the bug.

Stan Seibert

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