[Jack-Devel] jack1: jack_transport does not work as master

Tobias Hoffmann lfile-list at thax.hardliners.org
Thu Jul 2 14:20:26 CEST 2015


I'm still using debian's jackd1/libjack0 package (0.124.1) and have not 
tried to reproduce this with git master yet (at least, I haven't seen an 
obvious fix in the commit log since 0.124.1).

In one terminal window I run  jack_showtime.
In the other window I do:

 > tempo 96        # just in case
 > master
 > play                 # does not

jack_showtime correctly shows the state, but no BBT information. From my 
own client I know that jack_position_t::valid==0.

Some testing revealed that the timebase() callback in tools/transport.c 
is *not called at all*, although jack_set_timebase_callback is called 
and returns without error.
- But everything works fine when I switch to the jack2 stack...

And in some cases, when switching between/enabling/disabling different 
Transport masters,
jack_position_t::valid retains the JackPositionBBT flag (and stale 
information) -- but no-one updates them any more...

Maybe related: I've seen some strange values (*very* large negative 
number) for bar_start_tick when using ardour4.1.
The very first time (and after rewind?) it contains 0.0 and is not 
updated. A quick glance into the ardour source code reveals that this 
field is not implemented yet. I could probably live with that.
BUT: After stopping+starting the playback, these strange values 
appear... How can I know whether some value in this field is usable at 
all -- except for some heuristics?

Back to the original topic... in both cases the jack_position_t struct 
contains stale/random values, instead of starting from a "clean" base -- 
maybe memset(,0,) is all that is needed here?


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