Re: [Jack-Devel] Call for testing of MIDI Drivers in JACK 2

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DateMon, 18 Apr 2011 00:42:47 -0700
From Devin Anderson <[hidden] at charityfinders dot com>
ToNedko Arnaudov <[hidden] at arnaudov dot name>
CcJack devel <[hidden] at lists dot jackaudio dot org>
In-Reply-ToNedko Arnaudov Re: [Jack-Devel] Call for testing of MIDI Drivers in JACK 2
Follow-UpNedko Arnaudov Re: [Jack-Devel] Call for testing of MIDI Drivers in JACK 2
On Sun, Apr 17, 2011 at 3:15 PM, Nedko Arnaudov <[hidden]> wrote:

> I've made tests with jack2 jackdbus from svn trunk r4317. I've tested
> the alsarawmidi backend along with the alsa audio driver.

Excellent.  Thank you very much. :)

> The kernel I used is 2.6.33.7-rt29 with irq threads at default
> priorities (not tweaked).
>
> My hardware is a PCI emu10k1 card (SB Live! 5.1 Dell OEM [SB0228]).
> I have a 4 core Phenom II CPU.
>
> jack_midi_latency_test -m 3 -s 8192 -t 3 "system:1-1 EMU10K1 MPU-401 (UART) 1 out" "system:1-1 EMU10K1 MPU-401 (UART) 1 in"
> ---------------------
> Reported out-port latency: 2.67-2.67 ms (128-128 frames)
> Reported in-port latency: 2.67-2.67 ms (128-128 frames)
> Average latency: 6.26 ms (300.52 frames)
> Lowest latency: 5.75 ms (276 frames)
> Highest latency: 6.87 ms (330 frames)
> Peak MIDI jitter: 1.12 ms (54 frames)
> Average MIDI jitter: 0.25 ms (11.64 frames)

The jitter here closely resembles USB jitter.  Maybe the jitter here
is due to IRQ threads being at default priorities, though the jitter
is pretty evenly spread in the 1 millisecond range, which makes me
think that's probably not the case.  Maybe the sound card or driver
has a millisecond resolution for MIDI processing.  Not sure.

> I'd be happy if jack_midi_latency_test had an option for disabling the
> autoconnect behaviour. Instead, the test could be started when both
> ports are connected. What do you think about this idea?

I think that's a great idea.  I'm actually nearly done doing that now,
though I may go to sleep before pushing the code.

Question: Is the callback function set via
'jack_set_port_connect_callback' supposed to be realtime safe?  I
can't find the answer in the JACK documentation.

-- 
Devin Anderson
devin (at) charityfinders (dot) com

CharityFinders - http://www.charityfinders.com/
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