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Old 06-18-2010, 09:09 AM
Ralf Mardorf
 
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Daniel James wrote:
> Hi Ralf,
>
>
>> Btw. to the list and off-list more and more people subscribed to LAD
>> experience MIDI jitter on modern computers for every OS.
>>
>
> You're quite right to keep mentioning this issue, and I do appreciate
> the time you've put into testing to prove the point.
>
>
>> OTOH using the
>> rtai kernel patch, controlling CNC should be possible without micro
>> controllers. I wonder if Linux audio is using the best rt patch, resp.
>> if it's possible to use the rtai patch for audio too?
>>
>
> That patch is not something we've looked at yet, but I'm sceptical that
> the realtime kernel is the cause of your MIDI problems. If they got this
> right in the 80's, on computers which could not do anything near
> realtime audio processing, then I think it's more likely to be a
> question of MIDI application design. Have you tried running the test on
> Ardour 3?
>

No, I should compile Ardour3, but ...

> Also, we have less on-board MIDI controllers now, and more USB, which I
> suspect might be contributing to the problem.
>

... I suspect my USB MIDI device. Unfortunately I didn't get the MPU for
my Terratec 24/96 working until now. I'll mount my older PC again. This
older motherboard has got a MPU for the 'game port' where no external
opto-couplers are needed.

> Looking at the thread here:
>
> http://forum.cakewalk.com/tm.aspx?m=1178006&mpage=3
>
> it seems that Logic 5 and Logic 6 had tight MIDI timing, but in Logic 7
> it got worse. Other proprietary sequencers are reported as having really
> bad or variable jitter.
>
> Have you seen this page? http://openmuse.org/transport/fidelity.html
>
> See also this IBM paper from 2001:
> http://openmuse.org/noncpl/MIDIWAVE-ICMC2001.pdf
>
> Cheers!
>
> Daniel
>

I'll read it tomorrow. It's said that Nuendo should be ok, resp. even
for Nuendo there should be some limitations for external MIDI equipment,
but IIRC it's said that there should be less jitter to be fine with a
recording, when all external MIDI instruments are recorded at the same time.

Logic today is for MacOS only. I'm just interested in Non-Apple PCs, so
for tests Windows apps are welcome. Currently I don't have a Windows
install, but I had one on my machine and even if there was less jitter
for Windows, it was too much for external MIDI equipment too.

To be continued ...

Ralf
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Old 06-18-2010, 07:26 PM
Gustin Johnson
 
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On 10-06-18 02:54 AM, Daniel James wrote:
> Hi Ralf,
>
>> Btw. to the list and off-list more and more people subscribed to LAD
>> experience MIDI jitter on modern computers for every OS.
>
> You're quite right to keep mentioning this issue, and I do appreciate
> the time you've put into testing to prove the point.
>
>> OTOH using the
>> rtai kernel patch, controlling CNC should be possible without micro
>> controllers. I wonder if Linux audio is using the best rt patch, resp.
>> if it's possible to use the rtai patch for audio too?
>
> That patch is not something we've looked at yet, but I'm sceptical that
> the realtime kernel is the cause of your MIDI problems. If they got this
> right in the 80's, on computers which could not do anything near
> realtime audio processing, then I think it's more likely to be a
> question of MIDI application design. Have you tried running the test on
> Ardour 3?
>
> Also, we have less on-board MIDI controllers now, and more USB, which I
> suspect might be contributing to the problem.
>
Is there some way to test this?

I am using the MIDI controller on my RME card and I also have USB MIDI
controllers that I sometimes use with my laptop.

> Looking at the thread here:
>
> http://forum.cakewalk.com/tm.aspx?m=1178006&mpage=3
>
You are not going to see 1 ms timing with USB2 gear.


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Old 06-21-2010, 10:39 AM
Daniel James
 
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Hi Gustin,

>> Also, we have less on-board MIDI controllers now, and more USB, which I
>> suspect might be contributing to the problem.
>>
> Is there some way to test this?

For ALSA MIDI there is: http://github.com/koppi/alsa-midi-latency-test

Ralf has been using some of Fon's tools; you'll have to ask him about
the details of his methodology.

> You are not going to see 1 ms timing with USB2 gear.

That seems to be the case, but then USB is on every system and MIDI
sockets are not, which has skewed the keyboard and controller market
away from better technical solutions.

Even RME have two USB MIDI interfaces now (Fireface UC and Babyface). It
just makes me glad I kept my five-pin DIN MIDI cables :-)

Cheers!

Daniel
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Old 06-21-2010, 11:15 AM
Ralf Mardorf
 
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On Mon, 2010-06-21 at 11:39 +0100, Daniel James wrote:
> Hi Gustin,
>
> >> Also, we have less on-board MIDI controllers now, and more USB, which I
> >> suspect might be contributing to the problem.
> >>
> > Is there some way to test this?
>
> For ALSA MIDI there is: http://github.com/koppi/alsa-midi-latency-test
>
> Ralf has been using some of Fon's tools; you'll have to ask him about
> the details of his methodology.
>
> > You are not going to see 1 ms timing with USB2 gear.
>
> That seems to be the case, but then USB is on every system and MIDI
> sockets are not, which has skewed the keyboard and controller market
> away from better technical solutions.
>
> Even RME have two USB MIDI interfaces now (Fireface UC and Babyface). It
> just makes me glad I kept my five-pin DIN MIDI cables :-)
>
> Cheers!
>
> Daniel

Hi Daniel

I'm not sure if it's worth the effort. Perhaps I got 10 mails off-list
confirming this issue and another 10 mails off-list with name-calling
because it's again FUD and that there are millions of anonymous people
who ask to ban me from all Linux audio lists. So I guess I unsubscribe
to all Linux audio lists myself and repair my Atari ST.

Anyway, how to use the Fon's tool. Connect your hw MIDI out with your hw
MIDI in, that's it.

My tests were done by recording beats from external MIDI equipment, e.g.
a very short sinus (an impulse) from a DX7 at 120 BPM.
Then I zooooooooooooomed into the waveforms and searched for the
beginning of the waveforms, that's very hard work, because noise might
cover the start points.

120 BPM = every 500ms one beat, but recorded beats might be at 448ms or
502ms = - or + 2ms. I recorded many beats to see what's the max and
what's the min jitter.

Because an audio track might have latency and we can set offsets I did
max_jitter - min_jitter = effective_jitter

Cheers!

Ralf

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