[mythtv] ALSA Sound Driver Question

Ed W lists at wildgooses.com
Thu Jun 2 00:26:19 UTC 2005

>The "fragment size" is fixed at 4096 bytes, which means I need to feed the
>audio output with 4096 bytes before it will begin playing. At telephony
>rates this equates to 250ms, which is far too long a delay to insert into a
>phone call (I currently use around 40ms).

I guess also that the open function in each bit of code should probably 
have a look at the rate and decide on a sensible buffer size based on that.

It becomes a difficult heuristic though.  You find a bunch of cards 
which simply break if you want them to use buffer sizes smaller than X 
or larger than Y....

I think the best thing is just to have the flag I mentioned try and set 
the absolute lowest latency the card will stand (within reason, my pro 
RME card can so silly low levels...).  If the card can do less then 40ms 
then basically go as low as 10ms...

Either way it's going to need the individual driver hackers to fix 
this.  Suggest not worrying too much.  I will try and have a look as well

Ed W

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