Re: [Linuxsampler-devel] 24bit multi-io audio card compatibility, Was: CVS

[Mark K. <mar...@co...>]

On Tue, 2003-10-28 at 16:52, be...@ga... wrote:

> > 1) The first issue is that the Mellotron voice I'm playing is 10 seconds
> > long on GSt, at which point I hear it loop and start over. (Hit one key
> > and hold it for 30 seconds and you hear 3 passes.) However, LSt is only
> > playing the voice for 2 seconds and then quitting. It doesn't loop the
> > voice after 10 seconds, it just stops.
> 
> Keep in mind that looping is not implemented yes.

Yep, this turned out to be an aspect of that specific library. I loaded
up some really long gig files from a library called 'Drone Archeology'.
They can run over a minute long and they played correctly in LS. 

Not only that, but I recorded the same drone using GSt and LS into Pro
Tools and then looked visually at the two. With GSt set at full volume
the two looked basically identical in Pro Tools down at the sample
level.

> If LS is playing only for 2secs then it is playing a sample that is only.
> 2secs long. The wrong pitch is because LS is not honoring all the articulation
> parameters yet. Christian will at that soon.

Great.

> >
> > 3) Zooming way in while in Pro Tools shows the latency of LSt to be
> > slower than GSt. It doesn't look horrible, and I didn't try to measure
> > the difference as I don't have much time right now. We can focus on that
> > later.
> 
> Hmm this is interesting. How do you measure the latency ?
> Can you record both the time a midi event gets in and put that on the
> same time scale as the audio in PT ?
> 
> IIRC you played LS with --fragmentsize 256, lower this to 64
> it should give you a latency of 2*64 = 128 frames = 3msec
> 
> Please redo the test and tell us if the latency is correct
> (probably you need to add the 1.1msec of MIDI Note-on latency if you trigger
> LS via external MIDI device).

I will revisit this tomorrow when I have more time. I think my tests
need some corrections for sure. In LS I was using the 256 fragment size.
In GSt I was using a buffer size of 128. That will certainly account (I
think) for some of the reason that LS looked slower.

As for how I measured it, I set up both GSt and LS to be triggered by my
keyboard. The keyboard came into Linux on a MidiSport 2x2 input, and
then using kaconnect was routed to a MidiSport output to go out to GSt,
and routed directly to LS in software.

The LS output was then routed through playback_1/2 to the ADAT2-1/2
outputs and was recorded by Pro Tools.

In the GSt box MIDI goes in through an AP2496 MIDI port and triggers
GSt, which goes out over ADAT, into the HDSP 9652 where it is routed in
hardware to ADAT2-3/4 outputs where it is recorded by Pro Tools at the
same time as LS.

All I was looking at was the relative positions of the two stereo
signals in Pro Tools and seeing an offset with LS coming later.

I need to redo this with at least the same buffer size for the two
samplers.


One other interesting thing I did was to just brutally overload LS with
polyphony while using the drone library.Since you don't handle the
sustain pedal yet I simply laid my arms down on the keyboard covering
all the white notes for about 4 octaves and held them. All indications
were that all the notes played. Since this library's note length is
scaled by the keyboard position, the high notes cut out first, and then
lower and lower notes cut out as they run their length. Since you don't
loop yet, I can hear the notes drop out one by one. Everything seemed
correct.

This was quite good.

One small negative I found was during just simple playing, upon release
of a note I get definite little 'clicks' out of LS. I am guessing that
this is probably because you implement no ADSR yet? I'm sure that GSt
implements some standard release envelope to eliminate that problem. It
probably continues to play the voice for a few more samples as it ramps
the volume down to zero. If this is the case, then it's not a problem
and you just need to work on providing something like that when you can.

For technical reasons I couldn't get the Bardstown piano over to the
Linux box yet. It's compressed in an executable file. Is there some way
to run that in Linux, maybe using a DOS window or something? I've never
used dosemu or any form of DOS under Linux, so I don't know how to
proceed. 

I can probably copy the library to a 1394 drive and then mount it under
Linux. If there's no easier way to do it, then I will work on doing it
that way tomorrow.

I want to work on this as it will start to demonstrate LS's ability to
work with multi-velocity libraries.

Overall I'm very happy and MOST impressed by the two signal outputs
looking sample for sample identical in Pro Tools. That quite an
accomplishment considering (I think) that no one has looked at this
before me. Congrats to all of you!

Cheers,
Mark