[vlc-devel] Re: VLC audio output FIFO questions ...

John Michael Zorko j.zorko at att.net
Wed May 14 23:40:29 CEST 2003


> This is a known issue
> http://bugzilla.videolan.org/cgi-bin/bugzilla/show_bug.cgi?id=115

I can change one line of code in my hacked version of VLC to make this 
problem disappear ... this line of code basically specifies the number 
of times pf_demux() is called before seeking to whatever new point in 
the file the ff / rewind action would specify.  The amount of wobble in 
the audio seems inversely proportional to this number, which leads me 
to believe that whatever FIFO the audio output is reading from is 
measured temporally (amount of time in the buffer) vs. quantitatively 
(the # of packets in the buffer).  By making this number larger, I all 
but eliminated the wobble in my experiments.  My next trick <grin> is 
to try to locate the FIFO that this relates to, and configure it to be 
smaller to see if I see the same thing, in essence fixing it on the 
other end of the problem.  I'm not 100% positive, but this seems to 
make sense ... do you agree?

I'm a bit concerned about what side effects changing the size of this 
FIFO would be, since it's related to the audio output.  For instance, 
would this change break other sound architectures i.e OSS, ALSA, 
CoreAudio, etc.?  I know little about this stuff (me streaming / MPEG 
guy) but I think i'm going to get familiar with at least some of this 
stuff before this journey is done :-)

> I know fenrir solved it for some other stuff, it might be worth 
> looking into CVS logs of those.
> Fenrir himself might be able to give you some more help too.
> He's often in #videolan on Freenode IRC.

OK, I need to get a Mac OSX IRC client now :-)



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