On Mon, Aug 19, 2002 at 08:40:34PM +0200, Tim Goetze wrote: > > > >the former is difficult, because the queue is driven by interrupts > >from a timer source. that is, a sequencer client must give signals at > >the constant and fine period. this is not a job what a user process > >does.
Just nitpicking: The monotonicy is not required. The only thing needed is that the interval is known - so we can use dynamically variable clock frequency :-) > > > >the latter, controlling a queue, would be feasible. > >in this case, you can change the tempo or time skew dynamically by > >sending events via system-timer port (0:0) to a specified queue. > >but anyway, a queue must run individually from the client. > > > >maybe i can give more specific answer if i understand your question > >more clearly... > > OK, here goes. I have a core here that processes MIDI and PCM. There's > a RTC thread that controls event timing, synced to the sample clock. > So, internally, the application has a precise idea of the current > tempo, tick, time and frame. > > Currently, events sent to ALSA sequencer ports are sent via > snd_seq_event_output_direct(), with a 0 timestamp. > > Now what I'm looking for is a way to export this timer functionality > to the sequencer system, ie make it possible for other clients to > sync to this clock. > > tim > If I understand you correctly you actually want to slave ALSA to your application's timing source. I see 2 options for it (please correct me if I'm wrong since i've been away for too long): - sync the timer using SND_SEQ_EVENT_SETPOS_TIME events (and optionally SND_SEQ_EVENT_QUEUE_SKEW). ALSA remains running it's own clock (system clock, rtc, external clock), following your internal clock. - Use a PCM device as timing source (you'll need a reasonable small fragment size though). - Add support for a userspace clock source eg. add some "SND_SEQ_EVENT_CLOCK_ADVANCE" which would trigger a timer callback (hence snd_seq_timer_interrupt()). Cheers, Frank. -- +---- --- -- - - - - | Frank van de Pol -o) A-L-S-A | [EMAIL PROTECTED] /\\ Sounds good! | http://www.alsa-project.org _\_v | Linux - Why use Windows if we have doors available? ------------------------------------------------------- This sf.net email is sponsored by: OSDN - Tired of that same old cell phone? Get a new here for FREE! https://www.inphonic.com/r.asp?r=sourceforge1&refcode1=vs3390 _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
