On Tue, Feb 14, 2023 at 03:57:05PM +0100, Wim Taymans wrote: > > The real difference between the two methods is 'sample count' > > versus 'time' as the source of the event that starts a period. > > > > I always wondered why one would use a timer, it just amounts > > to polling. Suppose you look every 1 ms to check if there > > You don't need to use polling with timerfd, just set the timeout > according to some clock, > add the timerfd to some poll loop and it wakes up on time.
It's of course not 'active polling' (spending all CPU time on testing a condition), but it is still polling in the sense that it is NOT the event you wait for (having enough samples to start a Jack cycle) that wakes you up. When using a timer you just test for that condition periodically, which means you can be up to that period late. To avoid loss of period processing time, the timer period must a very small fraction of the Jack period time. And then I wonder what is the advantage. > Very much like how ALSA wakes you up when a period expires. AFAIK, ALSA doesn't use timers for that. For a sound card on e.g. a PCI bus the start of cycle would be the indirect result of an hardware interrupt. For USB or firewire cards, it would be triggered by an event from the lower (USB/firewire) layers. BTW, what about the 'signed differences' issue I pointed out earlier ? Ciao, -- FA _______________________________________________ Linux-audio-dev mailing list -- linux-audio-dev@lists.linuxaudio.org To unsubscribe send an email to linux-audio-dev-le...@lists.linuxaudio.org
