Hi Jack,
At Mon, 17 Sep 2001 20:06:48 -0600,
Jack Moffitt wrote:
>
> > Ah, I meant that total .851 msec for 5 minutes.
> > Thus it's still enough small. Sorry, I was too lame.
> >
> > I guess the problem is hidden somewhere in other place..
>
> I noticed that after I posted. Sorry.
>
> If this was the only drift, we'd have 16ms after an hour. Not _great_
> but probably acceptable for most things.
>
> I can't see where any other drift is really possible, since the
> snd_seq_timer_update_tick() is just doing += and %=, which doesn't leak.
>
> The only thing I can think of is that the sound card clock is drifting
> too.
Do you mean the drift as the difference between the "real" wall-clock
time and sequencer ticks? Or between the sequencer time and ticks?
If compared with real wall-clock, it may likely happen that pcm clock
drifts. As I measured with a test program (attached below), there is
a bit drift between measured and expected times.
And interestingly (or naturally), this drift is dependent on the sound
chip. CM8738 shows faster playback than SB Live.
Takashi
timertest.c
