26 Sep
2010
26 Sep
'10
1:21 a.m.
On Sunday 26 September 2010 01:08:21 Max Payne wrote:
Hi guys,
first of all forgive my not-so-perfect English :-)
I'm writing down some code for a minimal loop player based on two threads:
one handles a beat counter, the other feeds the soundcard with audio
frames, through ALSA. When the beat counter has completed a full cycle
(e.g. 4/4) it simply rewinds the PCM data to byte 0 making a seamless
loop. Really straightforward. Now, I'm wondering how to implement the
metronome side: should I rely on something like usleep/nanosleep or ALSA
layer could offer an advanced timer? Another potential issue would come
from latency, obviously present within the audio thread (due to ALSA):
what happens when the beat counter restarts the audio sample but an alsa
frame is still being written to the soundcard? Thank you in advance for
any suggestion!
Why do you part a task that belongs together?
The most trusted clock to relate samples to real world time (which you want
for your beats/bars) is the sampling-clock. Which you get from the alsa-
thread. Why even bother to do the time-keeping in a different thread? Do all
your audio-stuff in one thread.
You should use a different thread when disk is accessed. Or when you do long
running math that you only need to be finished for the audio-block after the
current (or even later). And you would have a different thread for the gui
stuff. Most probably this thread is called the main-thread:-)
Have fun,
Arnold