Re: [jazzplusplus-devel] Thoughts about the linux kernel - observed trends

[D.B. M. <db...@ho...>]

Greets,

> Date: Thu, 15 May 2008 22:31:41 -0400
> Subject: Re: [jazzplusplus-devel] Thoughts about the linux    kernel  -       observed        trends
>
> On Fri, 2008-05-16 at 02:03 +0000, D.B. Moore wrote:
>> Greetings,
>>
> (snip)
>>
>>
>> I think what I eventually might do, is put some sound files up
>> on our site, which **audibly** demonstrate to users artifacts
>> of sound quality directly related to linux kernel latency issues.
>>
>> That'd be about the best thing to do...IMHO....to help users
>> conclude whether or not they need a better (faster) kernel
>> for their setup. Hope this helps...
>>
>> Regards,
>>
>> Donald B
>>
>>
>
> I tried Jazz++ a couple of ways, both quite good:
>
> * my ux16 USB midi interface hitches to a Motif ES8 which together has
> excellent sound quality.
>

Good to hear...(another pun ;) No timing issues? Don't be scared to be verbose
if what you're doing relates directly to Jazz++'s performance in the real world.


> * The software synth I like is ZynAddSubFX produces its own pleasing
> sound. I use Hydrogen for its drum set. Rosegarden does this, and I
> think Jazz++ can too. (I didn't run Hydrogen from it yet.)

If you do, be sure to let us know if it works okay.  I do know about zyn & lv2,
in fact I've just installed that kit here on my box - but as is common with a lot
of us here, I haven't yet found the time to play with it....but I will get to it...

>
> Probably I need to modify the kernel to hear how good the native midi
> is.
>

You just know I'm going to ask what makes you think that, don't you?  ;-)


Subsequent to my previous posting, and carrying my notion forward
about putting soundfiles somewhere that people can listen to and then
conclude whether or not they have linux kernel latency issues with their
softsynth setup....

Pete,  can you put this attached mp3 file in..'some appropriate location'
for me please? I'm thinking about a yet undiscussed 'FAQ' area, and
anywhere else kernel latency issues are touched on, it'd be handy to
be able to link back to this location...I'm sure you get the idea here ;-)

Bob, listen to the attached mp3 and the sound of the softsynth loosing
the plot entirely, until timelag detection code realizes something gone
terribly wrong and realigns the datastream with where the hardware
is 'right now' as it were. .

This was rendered a few years ago now on a x86_32 with an AMD
athlon 3000+  CPU using AMS on one of my own linux builds. IIRC
the timing glitche started out as a 0.002 second deviance, rising to
0.09 second deviance before the code kicked itself in the pants.

Remember I said this area was a minefield?...yeah, well some of these
timing related issues are not entirely the  kernel or the software's
fault -- it can actually be related to the motherboard chipset being used
and/or the state of play with a particular chipset's driver (in linux).
A good example is what you hear in this mp3, which is going to be
heard a -lot- more by folks with a VIA chipset mainboard (x86),
because this is a known issue with linux/VIA chipsets, and it doesn't
affect just the things we're talking about here - DMA and interrupt
issues with VIA chipsets can plague the video, fb, any manner of things..

....and, just as an example of HOW weird and obscure this can get,
I have a VIA epia-tc10000 board here that initially gave me all sorts
of heck, and I did hours and hours of mucking around with it before
I discovered the effective fix was actually to email the VIA techsupp
crowd about it, who replied with a link to a beta version BIOS image
...so the problem was in BIOS all along, and seemingly only affected
use with a linux kernel...go figure...

Oh...and for the record, what you're hearing in this sound snippet,
(the sound you're supposed to hear :), is a free running AMS patch
I did up for an arty friend who wanted some kind of eerie spacey
sort of ambiance as a sound prop for her display installation. I used
to call this patch "Trapped on a Dalek spaceship with the BBC
Radiophonic Orchestra"   ;-)

Regards,

Donald B



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