[LAD] Jack latency handling (Re: Software for recording digital audio?)

[Kjetil S. Matheussen]

Robin Gareus:
> >
> > 0.49 has this feature implemented. Use the "-jt" option.
> >
> > It should be sample sync,
> 
> Almost. It does not yet compensate for port-latency. It is important for
> both effects that introduce latency as well as to keep physical I/O in
> sync with apps.
>
> see jack_port_get_latency() and jack_port_get_total_latency()
> at http://jackaudio.org/files/docs/html/group__PortFunctions.html
>

Thanks for the info! I also wonder, does jack compansate for
latency when it mixes the outputs from ports (i.e. when several
output ports are connected to a jack_capture port), so that
the sound is in sync?



> > but I'm not sure whether the last
> > block (the one that received a stop message from jack transport)
> > should be recorded? For now it's recorded. If that's wrong,
> > I'll fix it in the next release.
> 
> While it's safe to just record it, i don't think it should be.
> http://jackaudio.org/files/docs/html/group__TransportControl.html reads:
> 
> jack_transport_stop() [..] takes effect on the _next_ process cycle.
> 
> jack_transport_query() [..] If called from the process thread, pos
> corresponds to the first frame of the _current_ cycle and the state
> returned is valid for the entire cycle.
> 
> IOW: As soon as the app sees a stopped transport in the process loop it
> is exactly at, or already a bit later than the actual end.
>

Thank you very much. This also confirms what I though was most likely.