Benno, you kick ass,
> > I was using O_RDWR | O_NONBLOCK, under a 2.2 kernel. I was trying to do
> > drumrolls, 16th notes, at 140bpm or 150bpm. It was no good.
>
> hmmm, really strange:
> I wrote a little util called mididelay, which writes a note-on MIDI message on
> the midi-out port reads back the message and measures the delay.
Can I get a copy of this program? Are you just using gettimeofday()
before and after, or are you using ptrace or some other hackery?
> BTW: which card are you using ?
For MIDI I'm using a Roland MPU-IPC-T card. MPU-401.
> > One requirement for ttrk was that it be able to trigger samples on beat,
>
> I'd suggest to use the raw /dev/dsp and the raw /dev/midi interface:
> [...]
Thanks for your suggestions. I'm hacking at it now...
> Do not forget to apply the lowlatency patches, or your timing will
> simply suck ! even an untuned IDE disk, when it reads/writes a small
> amount of data from/to the disk, could cause 20-50ms delay in your app
> and this is very bad for MIDI. ( see my tests , especially the non DMA
> ones = horrible :-) )
What lowlatency patches?? kernel patches?? That's just ugly. Where
can I get them?
> > > > What about syncing multiple soundcards?
>
> yes, this is far from trivial, but we will try to provide some usable
> solution: mainly activating the cards by using DSP_SET_TRIGGER (if
> supported, otherwise it's a real pain), to minimize starting delays,
> and then use one of the soundcards as source (or alternatively other
> timer sources), and put the remaining cards into a "slave" mode, where
> you measure the sample differences in audio buffers, and insert
> additional or drop samples to keep things in sync.
How can you tell if you've underrun under OSS? Using ALSA, I guess you
can use it's time stuff to calculate if you've missed a frame, but even
that seems hacky.
Do you just always use gettimeofday() math to keep track of how much
stuff you've written, and when skips have occured?
I don't like using one dsp as the sync master since I always want to be
able to sync to something external, like MIDI.
So, the problem becomes, how do you sync many soundcards and have it all
synced off external MIDI. :)
--
Billy Biggs [EMAIL PROTECTED]
http://www.div8.net/billy [EMAIL PROTECTED]
