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Old 07-05-2010, 08:25 AM
Ralf Mardorf
 
Default MIDI jitter - Today for 4 of 4 tests my USB device did pass all tests with success

On Mon, 2010-07-05 at 10:15 +0200, Ralf Mardorf wrote:
> -------- Forwarded Message --------
> From: Ralf Mardorf <ralf.mardorf@alice-dsl.net>
> To: Clemens Ladisch <clemens@ladisch.de>
> Cc: Linux Audio Developers <linux-audio-dev@lists.linuxaudio.org>
> Subject: MIDI jitter - Today for 4 of 4 tests my USB device did pass all
> tests with success
> Date: Mon, 05 Jul 2010 10:14:21 +0200

> I'm very sceptic regarding to the ALSA MIDI latency test, OTOH the PATA
> might have caused 7 ms and IIRC 19 ms too and visually interpretation
> might mistake because it's hard to find the start of waveforms in the
> noise.

I guess (don't know), that 7 ms and 19 ms are caused by a broken HDD,
but when I did the visually test the HDD wasn't broken, I did it a long
time ago.

So the visually test around 4 ms and ALSA MIDI latency test around 4 ms
from today might be correct results for my computer and at least when I
got 4 ms for the visually test, the audible result was unusable for
music, anyway, I still have got some hope.

To be continued ASAP.

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Old 07-05-2010, 08:47 AM
Ralf Mardorf
 
Default MIDI jitter - Today for 4 of 4 tests my USB device did pass all tests with success

On Mon, 2010-07-05 at 10:33 +0200, Arnout Engelen wrote:
> On Mon, Jul 05, 2010 at 10:25:23AM +0200, Ralf Mardorf wrote:
> > So the visually test around 4 ms and ALSA MIDI latency test around 4 ms
> > from today might be correct results for my computer
>
> That sounds pretty good then.
>
> > and at least when I got 4 ms for the visually test, the audible result was
> > unusable for music, anyway, I still have got some hope.
>
> You might have mentioned it before, but how exactly are you performing your
> test of the 'audible result'?
>
>
> Arnout

The hardest test is to record a MIDI groove for kick, snare and hihat.

I then used my Alesis D4 drum module that don't cause audible jitter
when using it with the C64 and Atari ST.

I did record the audio output of the Alesis D4 by Linux, but each
instrument one after the other, each instrument two times.

The result:

Playing one recording of the two recordings for each instrument and the
groove is broken. It doesn't matter if it's a beautiful McCoy Tyner or a
stupid Madonna like groove.

Playing two recordings, but just of one instrument the phasing is not a
constant phasing, but fluctuating. An early reflection similar effect
usually isn't the result, but in the worst cases even this is possible.

Ralf


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Old 07-05-2010, 08:51 AM
Ralf Mardorf
 
Default MIDI jitter - Today for 4 of 4 tests my USB device did pass all tests with success

On Mon, 2010-07-05 at 10:47 +0200, Ralf Mardorf wrote:
> On Mon, 2010-07-05 at 10:33 +0200, Arnout Engelen wrote:
> > On Mon, Jul 05, 2010 at 10:25:23AM +0200, Ralf Mardorf wrote:
> > > So the visually test around 4 ms and ALSA MIDI latency test around 4 ms
> > > from today might be correct results for my computer
> >
> > That sounds pretty good then.
> >
> > > and at least when I got 4 ms for the visually test, the audible result was
> > > unusable for music, anyway, I still have got some hope.
> >
> > You might have mentioned it before, but how exactly are you performing your
> > test of the 'audible result'?
> >
> >
> > Arnout
>
> The hardest test is to record a MIDI groove for kick, snare and hihat.
>
> I then used my Alesis D4 drum module that don't cause audible jitter
> when using it with the C64 and Atari ST.
>
> I did record the audio output of the Alesis D4 by Linux, but each
> instrument one after the other, each instrument two times.
>
> The result:
>
> Playing one recording of the two recordings for each instrument and the
> groove is broken. It doesn't matter if it's a beautiful McCoy Tyner or a
> stupid Madonna like groove.
>
> Playing two recordings, but just of one instrument the phasing is not a
> constant phasing, but fluctuating. An early reflection similar effect
> usually isn't the result, but in the worst cases even this is possible.
>
> Ralf

C64 synced by click and Atari ST synced by SMPTE and the recordings done
by a Yamaha MT44D 4-track cassette recorder a groove wasn't broken and
the phasing was fixed, absolutely constant. Using the same Alesis D4.

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