Re: Real-time category

[Travis Hartnett <travishartnett@gmail.com>]

My understanding of the main practical difference for loopers between
RTOS and non-RTOS is that in the first case there's a guarantee on the
maximum time the system will take to process an event.  In the case of
the EDP I seem to recall 1.5ms as the magic number.  Everything is
read in 1.5ms, all the time.  In a non-RTOS, the overall response lag
may average at 1.5ms (although I seem to recall that Windows and Mac
OS take slightly longer than this), but there are times when another
task might have precedence, and so the looping app response drops down
to something like 20ms.

20ms can be a problem if you were trying to an event (say "start
recording") with an upcoming MIDI downbeat from your drum machine.  If
you press the switch 15ms before the downbeat, expecting that the app
will read that and then wait until the next downbeat before recording
starts, but instead the "start record on the next bar" waits a bar
until the bar after the one which you intended.  Of course, this can
happen in an RTOS device, but it's much less likely with a 1.5ms
response time versus a sporadic 20ms.

On 12/7/05, Jeff Larson <Jeffrey.Larson@sun.com> wrote:

>
> I respectfully disagree.  The reasons have not been stated clearly, at
> least not to the level of clarity that I expect when conversing
> with other engineers.
>
> I'm not trying to argue, I genuinely want to understand what
> statements like this mean:
>
> [Kim]
>  > Looping happens to be a very time sensitive application, since users
>  > constantly interact with it in a rhythmic fashion and timing 
>inaccuracies
>  > tend to get multiplied as the loop repeats.
>
> This doesn't make any sense to me and no one has been able to offer an
> adequate explanation.
>