Re: [LAD] [64studio-users] MIDI jitter

2010/7/3 Ralf Mardorf <ralf.mardorf@alice-dsl.net>:
> On Fri, 2010-07-02 at 14:51 -0700, Niels Mayer wrote:
>> sudo alsa-midi-latency-test -w 20 -r -R -i 36:0 -o 36:0
>
> Perhaps better without sudo.

I was just following Paul Davis' lead (*).

For me, there's probably no need for this, as my user 'npm' has
membership in group jackuser spec'd in /etc/security/limits.conf :

> ## Automatically appended by the Planet CCRMA jack-audio-connection-kit
> ## NPM changed '*' to @jackuser to limit priority escalation to jackd.
> @jackuser - rtprio 99
> @jackuser - memlock 4194304
> @jackuser - nice -10

And /etc/group has entries like:

> jackuser:x:476:npm
> rtkit:x:470:npm

Running as root sidesteps the need for such setup, as well as any
permissions issues on the devices under test. From what I can tell,
the only privileged access in the test program is indicated by the
following output from 'alsa-midi-latency-test':

> set_realtime_priority(SCHED_FIFO, 99).. done.

.............................
(*):
On Fri, Jul 2, 2010 at 4:50 AM, Paul Davis <paul@linuxaudiosystems.com> wrote:
> just for comparison, here are the results for an RME Digiface:
> sudo /usr/bin/alsa-midi-latency-test -w -r -R -i 20:0 -o 20:0
> ...
>  best latency was 0.00 ms
>  worst latency was 1.00 ms, which is great.

Better if Paul re-ran the test with "-w 20" argument so his fancypants
RME doesn't end up unfairly claiming the 0ms latency title :-) ...

Who will claim the low-latency, low-jitter title in this epic
battle-of-the-geek:
VLSI-implemented midi on the VT1712 or RME's custom FPGA programming??
[[ http://old.nabble.com/Is-RME-HDSPe-AES-supported-by-alsa--td28460997.html
]].

Note that RME's FPGA implemented MIDI and mixer lacks an important
feature we get on cheap vt1712 VLSI implementations:
MIDI control over the built-in digital mixer via envy24control:
http://alsa-tools.sourcearchive.com/documentation/1.0.22-1/midi_8c-source.html
(yes there's a built-in midi-controllable, 20 channel, 36-bit digital
mixer hidden in that cheap ebay vt1712 --
http://www.via.com.tw/en/products/audio/controllers/envy24/ ).

Digital mixing is an important feature of RME's TotalMix :
http://www.rme-audio.de/en_support_techinfo.php?page=content/support/en_support_techinfo_hdsp_totalmix_hardware
But MIDI control of that mixer seems to be lacking in alsa's hdspmixer
and RME's implementation:
http://www.rme-audio.de/forum/viewtopic.php?id=6105

-- Niels
http://nielsmayer.com

PS: worlds' cheapest digital mixing console, take old/slow computer,
add linux and these:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230491593275
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260501295877
_______________________________________________
Linux-audio-dev mailing list
Linux-audio-dev@lists.linuxaudio.org
http://lists.linuxaudio.org/listinfo/linux-audio-dev
Received on Sat Jul 3 20:15:04 2010