JAVA a cross-platform language? I have my doubts! - Page 2

willemjav · #21 (**permalink**) 10-20-2008, 01:52 PM

If the pc timer can´get any better than 18 milliseconds.
What timer should one be using when doing signal processing?
JAVA is no good for real time stuff?
or should one look for a dramatical different approach when
going into SP?

Norm · #22 (**permalink**) 10-20-2008, 04:41 PM

For the Wait statement all the times are the same. Look at the args for wait() . I guess the nanosecs don't do anything???
For the Spinloop the times vary with the delay time.

willemjav · #23 (**permalink**) 10-24-2008, 12:54 AM

For the moment I do not see how to tackle this
problem. So I should live with the fact that
the program runs well on mac but and can not
run on pc because clock can not do
any better than 15 msec (tracks take double of the time)

Norm · #24 (**permalink**) 10-24-2008, 09:14 PM

Quote:

because clock can not do
any better than 15 msec

I thought my spinloop using nanotime could repeatedly call a method in less than 15 msec.
But maybe I'm mistaken

fishtoprecords · #25 (**permalink**) 10-24-2008, 09:23 PM

Quote:

Originally Posted by Norm

I thought my spinloop using nanotime could repeatedly call a method in less than 15 msec.

I'm pretty sure that timer resolution is platform implementation defendant.

For many versions of Windows, 18 mSec was as small as you could get reliably.

willemjav · #26 (**permalink**) 10-24-2008, 09:45 PM

Maybe a silly question?
How does one do signal processing on PC,
with anything finer as 18 mSec?

fishtoprecords · #27 (**permalink**) 10-24-2008, 10:56 PM

Quote:

Originally Posted by willemjav

Maybe a silly question? How does one do signal processing on PC, with anything finer as 18 mSec?

Allow me an edit, PC => Windows box.

Think about it a few seconds. early versions of Windows the OS will not reliably resolve times below 18 msec. If you are inventing something, say an audio capture card, that needs much better timing, what do you do?

The obivious choices are:
1) use something besides windows
2) do it before the signal gets to windows

For most products, #1 is a loser, since 90% of the world's PCs run Windows, and you will not have a mass market for your product if it uses some weird OS.

So how do you do #2? Its easy, use a driver. Design your product to require a driver, put all the magic in the driver or firmware on the card.

willemjav · #28 (**permalink**) 10-25-2008, 12:33 AM

could java get to that chard and ignore window box?

willemjav · #29 (**permalink**) 10-25-2008, 12:38 AM

what are the changes with linux
lunix runs on pc and java
communicates with linux?

fishtoprecords · #30 (**permalink**) 10-25-2008, 01:08 AM

Quote:

Originally Posted by willemjav

could java get to that chard and ignore window box?

I can't follow this, can you try rephrasing it?

fishtoprecords · #31 (**permalink**) 10-25-2008, 01:10 AM

Quote:

Originally Posted by willemjav

what are the changes with linux? lunix runs on pc and java communicates with linux?

Linux is a different Operating System than Windows. They have nearly nothing in common.

But to do serious timing stuff, you need a driver for linux as well. There are drivers for a lot more weird stuff for Windows XP than there are for Linux

willemjav · #32 (**permalink**) 10-25-2008, 01:11 AM

Could the driver that reach the card be written in java?
Java runs on jvm which uses windows?
It is all a little confusing?

fishtoprecords · #33 (**permalink**) 10-25-2008, 01:16 AM

Quote:

Originally Posted by willemjav

Could the driver that reach the card be written in java? Java runs on jvm which uses windows? It is all a little confusing?

You need to do some research on realtime devices, drivers, etc.

Drivers are nearly always written in C or assembly language. They run in protected space, within the O/S. They are not user programs.

Whether or not you could get access to the driver from Java depends on too many things for me to answer. Its implementation dependent.

You might be able to do it with JNI, but JNI is really no longer Java.

You really have some fundamental confusion here about the basic concepts of how device drivers work, what access is allowed, etc.

willemjav · #34 (**permalink**) 10-25-2008, 01:19 AM

Anyway what would be the situation of the 18 msec window timer
compared to possible linux timers that java could implement?
I mean to say could I find a higher resolution of timers at linux?

willemjav · #35 (**permalink**) 10-25-2008, 01:26 AM

At the moment I can reach a 1 msec resolution on mac os and
maybe go beyond that!
I am also studying K. sierra´s book that deals with java´s
grammatical issues which I do not master still. I´ll first read that through.