[mythtv] [PATCH] Alsa audio sync and other fixes for latest big audio update

Ed Wildgoose lists at wildgooses.com
Fri Nov 5 18:25:55 UTC 2004

>Some soundcards (mostly the emu10k1 based soundblasters, iirc) have _huge_ 
>buffers - up to a couple seconds.  With the 'audio_buffer_unused' stuff, it 
>tries keeping the buffer size down a bit to improve performance during those 
>times where we wait for the buffers to drain (channel/input changes, mainly).

Hmm, OK, that makes much more sense.  I can't see that it is on a switch 
though (eg aggresive buffer settings) like David suggested?

What about if there were some more heuristics here?  eg NumBuffers * 
BufferSize > (say) 0.5 secs, then reduce buffer size a little?

The point is that although I don't use alsa, in my case I have a pro 
audio card and most of these are locked at two sample periods only 
(although the periods can be quite large...)  I think this code might 
cause problems for me?  I would have changed it before, but I was unsure 
if I was missing somthing more subtle, thanks for clearing this up.

While we have David's interest it might be a really good time to flush 
out all remaining the audio bugs?  Would it be sensible that when all 
these updates are in that we put a small announcement on the users list 
to try and get a little testing from problem users?  The main issue I 
see is encouraging users who already have problems (possibly due to 
config only) to try and play with cvs code..?  What do you think?


Ed W

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