On 01/29/2013 01:55 PM, D. Michael McIntyre wrote:
I don't have a clue why Rosegarden is causing this and MusE isn't. Upon
a superficial and quick comparison, they both appear to work the same
way in the case where QSynth is already running, and it's configured to
use pulseaudio: they both start with audio support disabled, due to
being unable to start jackd, because pulseaudio has control of the
hardware.
Michael, and all:
Perhaps that is a significant clue to the problem.
JACK seems to have made great strides lately. Where it used to not
co-exist with anything, it now seems to get along with most everything.
You can now play Internet videos with sound while JACK (QjackCtl) is
running, and can run all sorts of things together with it. On the
other hand, Audacity doesn't get-along with it at all.
If you look in the QjackCtl "Connections" dialog, in the "Audio" tab,
you now see a "PulseAudio JACK Sink" and a "PulseAudio JACK Source"
device. And the ubiquitous hangs seem much harder to cause.
I had concluded, based on my testing on several desktop computers in
my test-bed, that they had finally solved all of the problems, and
that JACK nicely gets along with everything. They seem to have even
put those fixes in the Long-Term-Support release, 12.04, because it
behaves just as well.
But then I tried the same test on my Acer Aspire laptop, and my new
MIDI device initially trying to use the (PulseAudio) Java Sound
synthesizer (with QjackCtl already running), hung it tighter than a
drum, and I had to power the machine down.
So I guess all is not yet well on the JACK audio front.
The significant clue in what you said, was that Rosegarden would fail
to start jackd, and would thus start up without audio support.
In doing the test, there was no warning about audio support being
disabled (that I in the past always used to see in such situations).
Where they now co-exist better, it probably succeeded in starting
jackd. But perhaps, they don't successfully co-exist in other ways.
As you pointed out, running with JACK is much more efficient. Where
processor usage was around 75% using PulseAudio, the same piece played
using JACK had a processor utilization of around 25%, which is no
insignificant difference. To even get it to work without cutting-out
on PulseAudio, I had to disable both the Reverb and the Chorus. I can
use them when I use JACK in place of PulseAudio.
By the way, most of my testing was done on an Intel Celeron CPU 2.53
GHz desktop machine, running Lubuntu 12.10.