[LAD] audio/midi app development

[Ralf Mardorf]

Arnold Krille wrote:
> On Tuesday 15 June 2010 17:55:56 Paul Davis wrote:
>   
>> On Tue, Jun 15, 2010 at 11:27 AM, James Morris <james at jwm-art.net> wrote:
>>     
>>> Incidentally, if I want the GUI to update very close to real time, say
>>> a grid of blocks flashing on and off as notes come and go, any
>>> thoughts? Would a GTK GUI update fast enough?
>>>       
>> key insight: your display monitor only redraws between 60 and 90 times
>> per second. attempting to redraw anything more frequently than this is
>> simply wasting CPU cycles and making your life more difficult. put
>> more bluntly: it doesn't matter if you have notes turning on and off
>> 1000 times per second - you and your users not working on a display
>> device that can possibly show this.
>>     
>
> Unless you make your lights "slowly" go on an off with transitions, there isn't 
> even a need to be faster then 25 or 30 updates per second. The slowest part 
> here is the human eye. And the requirement for >60Hz refresh rate for pictures 
> comes from the good old days of CRT screens.
>
> Arnold

Because I'm doing graphical art work some times I still prefer old 
faithful CTR screens, currently the refresh rate of my monitor is at 
89.9 Hz. But to be honest, the MIDI-thru-box I build in the 80ies and 
I'm still using it today, has a LED and the light is 'slowly' ... we 
aren't birds ... humans are fine with less than 30 frames/second for 
films and I guess nobody, excepted of some autistic people, are/is able 
to count how often a light is turning of and on within e.g. 30 
frames/second, but we notice any refresh rate under 75 Hz.

Regarding to updates for real-time GUIs it might be not important to 
display a virtual LED showing each MIDI event, but I can confirm that an 
ATARI ST + blitter (a coprocessor) has a more real-time near GUI for 
MIDI events, than Linux on my 2.1 GHz dual-core AMD. I'm not sure if 
it's needed. I also did use Atari STs without a blitter and the GUIs are 
less real-time than my Linux machine.

But this reminds me to my trouble using Linux MIDI with external 
equipment. There is jitter, that by theory isn't audible, but de facto 
it's audible, at least for chamber music like jazz.

Indeed IMO there should be more real-time for MIDI real-time on Linux.

The same old 2 cents,
Ralf