On February 20, 2010 02:38:19 pm Tim E. Real wrote: > On February 20, 2010 01:19:52 pm Paul Davis wrote: > > On Sat, Feb 20, 2010 at 11:03 AM, Ralf Mardorf > > > > <ralf.mard...@alice-dsl.net> wrote: > > > If Linux apps would use JACK transport the coders only would have to > > > take care to handle this. Just having on app doing sync among JACK and > > > eternal MIDI would reduce the risk of trouble. Btw. MTC should be part > > > of such an app too ... I didn't read the whole thread, perhaps this was > > > mentioned before. > > > > this isn't true. > > > > one of the most deliberate and conspicuous design decisions of the > > JACK transport API is that there is no support for varispeed. > > > > sync requires knowing two things: where we are, and how fast we are > > going. JACK transport has only 2 answers the the second question > > (stopped, rolling). this isn't adequate to fully capture the notion of > > sync. > > MTC: Maybe veering OT a bit but if we could just touch on this for a > moment. Was going to ask about this anyway, as we had talked about it a > bit. > > I thought "it's too bad we can't adjust Jack's sample rate on the fly" > thus allowing Jack to behave like a Voltage Controlled Oscillator in a > PLL, syncing to MTC frame. > I was thinking the VCO 'control' signal would come from a client. > Else Jack itself would have to support MTC. > > But raises the question - which Jack back-ends allow dynamic sample rate > changes? And with a finite resolution small enough? > > I concluded that the best way for me to sync Jack audio with an > external MTC is with app-side audio time stretchers. I forgot to add that if one is faced with external MTC (or any frame-based sync signal) then it should really be fed (somehow) into the sound card as a sync signal, shouldn't it? Everything supports SPDIF, but MTC? Then sound card + Jack + apps are happy, as they all run off it.
And using MTC to send sync between apps just seems odd, as they're using Jack already, for audio. _______________________________________________ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
