[LAD] SMPTE and jackd

Ralf Mardorf ralf.mardorf at alice-dsl.net
Fri May 11 05:34:52 UTC 2012


On Fri, 2012-05-11 at 07:26 +0200, Ralf Mardorf wrote:
> On Fri, 2012-05-11 at 04:32 +0200, Jens M Andreasen wrote:
> > On Tue, 2012-05-08 at 11:21 -0400, Paul Davis wrote:
> > 
> > > first of all, MTC is not a particularly reliable protocol unless you
> > > can dedicate the equivalent of a MIDI cable to it. its data rate gets
> > > close to the serial MIDI limit,
> > 
> > Using MTC quarterframe messages uses no more than 240 bytes/second, less
> > than 1/10th of the bandwidth:
> > 
> > http://en.wikipedia.org/wiki/MIDI_timecode#Quarter-frame_messages
> 
> "When the time is running continuously" - Wiki
> 
> On Tue, 2012-05-08 at 11:21 -0400, Paul Davis wrote:
> "the problem is that many receivers (even if
> they do not transmit MTC in the "canonical way"  - i.e. actually
> emitting a quarter frame message at a fixed interval) expect to
> receive it in canonical form"
> 
> "MIDI Time Code
> 
> For device synchronization, MIDI Time Code uses two basic types of
> messages, described as Quarter Frame and Full. There is also a third,
> optional message for encoding SMPTE user bits." -
> http://web.media.mit.edu/~meyers/mcgill/multimedia/senior_project/MTC.html
> 
>  - Ralf

PS: So if only Quarter Frame is supported, you'll run into trouble, as I
often did. As I already pointed out. I experienced that device A can be
slave of device B, but device B can't be slave of device A. That's why
Paul explained it (to us/me) and he's right.




More information about the Linux-audio-dev mailing list