Re: Accuracy of timestamping streamed data (code included - long)
Re: Accuracy of timestamping streamed data (code included - long)
- Subject: Re: Accuracy of timestamping streamed data (code included - long)
- From: Dado Colussi <email@hidden>
- Date: Mon, 25 Sep 2006 23:45:48 +0200
I'm not an expert in this but reading thought your code my initial
suspicion is on the use of timers. I would have the reader thread
directly call the -read method in its main loop and use nanosleep()
for waiting for next time to read data.
Dado
On Sep 25, 2006, at 23:07, Hank Heijink wrote:
Hi everyone,
I'm new to this list, and fairly new to Cocoa (although by now I've
worked my way through Hillegass and Dalrymple + same). I'm working
on the following problem:
For an application in behavioral science, I'm recording cursor
movements on an old (10+ years) and big (3 by 5 feet) Quora
digitizing tablet. The tablet streams 6-byte coordinates at a
constant rate of about 160 Hz, and I want to get as constant a
recording rate as I can get. After saving my data to a file, I find
I'm fairly accurate, that is, I've timestamped my coordinates such
that they're between 5 and 7.5 ms apart. The standard deviation of
the differences in time is about 0.3 ms.
My question is, can I achieve even better accuracy, and if so, how?
I'd like a more constant rate - I know the output rate of the
tablet is more constant than this, and I'm not sure what causes the
variability. My application is built in release mode and it's the
only one running. Not sure if background daemons are having an
effect and I don't know much about USB timing accuracy, but I guess
at this level of accuracy, everything could have an effect...
I hope I'm clear... Any thoughts are much appreciated!
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden