Subject: Re: [linux-audio-dev] introduction & ideas
From: Paul Davis (pbd_AT_Op.Net)
Date: Tue Mar 05 2002 - 19:48:25 EET
>IMHO a MIDI driver should be a (real time) user space process able to
>accurately transmit MIDI events on the hardware from
>CLOCK_MONOTONIC or something similar.
IMHO, to "accurately transmit" means that you have to be able to
schedule with an accuracy at a resolution of 1 MIDI byte (320usec).
CLOCK_MONOTONIC cannot, by itself, accomplish this, and isn't
necessary. One might say its an unnecessary and insufficient condition :)
What is needed is an extraordinarily (by comparison with most systems)
high resolution timer. This can only be provided by (1) a device like
the timer on the old GUS boards or (2) something like what the KURT
patches do (constantly reprogram the system timer to interrupt when
needed).
Without them, I don't see how this can ever be done with the correct
timing. I define correct to be the timing that would be obtained from
a device driver that blocked all interrupts but its own, and had a
queue of say 4kB of MIDI data that it delivered in an uninterrupted
stream via a h/w MIDI port.
--p
This archive was generated by hypermail 2b28 : Wed Mar 06 2002 - 00:36:25 EET