[Ardour-Users] A3 MIDI latency adjustment technique/advice

[Ralf Mardorf]

On Thu, 2013-11-14 at 17:54 +0100, Robin Gareus wrote:
> On 11/14/2013 04:28 PM, Ralf Mardorf wrote:
> 
> [..]
> > MIDI can be perfectly in unison with recordings. I never had issues
> > regarding to jitter when using a C64 or Atari ST.
> 
> ..or any other hardware that has dedicated hardware support.

C64 = no multi-tasking and direct access to the UART/ACIA + the
possibility to turn of IRQ :).

> [..]
> > USB-MIDI is completely unusable.
> 
> nope. While the USB bus itself is far from ideal, it's mainly the vast
> majority of prosumer USB audio+midi devices out there that are unusable.

I didn't know that.

> jack1 has seen recent updates

I had no time to test it until now, but build and installed it already
in July.

$ pacman -Qi jack1-git
Name           : jack1-git
Version        : 0.121.3.58.g5820385-1
Build Date     : Sat 20 Jul 2013 08:44:05 PM CEST
Install Date   : Sat 20 Jul 2013 08:49:11 PM CEST

Usage is still on my todo list :).

Thank you for the information.

Regards,
Ralf

PS: I found some notes from a C64 BASIC extension I once wrote :D.

[snip]

$1805 LDA #$03  ; MRESET
$1807 STA $DE04
$180A LDA #$12  ; BAUD
$180C STA $DE04
$180F RTS       ; BACK TO BASIC

$1810 LDA $DE06 ; WAIT FOR BYTE
$1813 LSR
$1814 BCC $1810
$1816 LDA $DE07 ; READ BYTE
$1819 RTS

$181A SEI       ; IRQ OFF
$181B JSR $1810
$181E CMP $1804 ; TEST BYTE FOR SOME CONDITION
$1821 BNE $181B

[snip]

$183C CLI       ; IRQ on

[snip]

$DExx "seems" to be the registers of the UART ;). IOW there is no layer to
communicate with the interface.