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RE: [linrad] FFT performance
- Subject: RE: [linrad] FFT performance
- Date: Fri, 15 Nov 2002 16:58:24 +0900 (JST)
Thanks for taking the time with me on this issue.
On Thu, 14 Nov 2002, W3SZ wrote:
> Hi, Edson!
> A similar thing happened to me a long time ago on my Pentium Pro 200. I
> don't remember the details (more than 2 years ago, I think) but I think
> the following:
> Three things:
> 1. Does the same thing happen when you type "A" for weak signal Cw
> or "D" for SSB as it does when you type "F"?
It does happen on the other modes as well.
> 2. There may be a parameter file there that is causing problems.
> Look for par_userint in the 'lir' directory where linrad is. It may be
> that the adspeed is set to 48000 or something that overtaxes your cpu
> (though it shouldn't). I attached par_userint listing below to show you
> what my parameters are. But this may be too much for your machine. Try
> setting the AD speed to 11025 or something even lower. You can edit
> this file on your machine with a text editor.
> vga mode 
> font scale 
> mouse speed 
> input mode 
> rx channels 
> ad channels 
> ad speed 
> ad device no 
> ad device mode 
> ad frag 
> da device no 
> min da speed 
> max da speed 
> max da channels 
> max da bytes 
> min da channels 
> min da bytes 
> check 
This is my par_userint
vga mode 
font scale 
mouse speed 
input mode 
rx channels 
ad channels 
ad speed 
ad device no 
ad device mode 
ad frag 
da device no 
min da speed 
max da speed 
max da channels 
max da bytes 
min da channels 
min da bytes 
> My par_wcw file (for mode 'a') is:
> First FFT bandwidth (Hz)  200
> First FFT window (power of sin)  0
> First forward FFT version  may need to make 1 or 2
> First FFT storage time (s)  4
> First FFT amplitude 
> Enable second FFT 
> First backward FFT version 
> First backward FFT att. N 
> Second FFT bandwidth factor in powers of 2 
> Second FFT window (power of sin) 
> Second forward FFT version 
> Second forward FFT att. N 
> Second FFT storage time (s) 
> Enable AFC/SPUR/DECODE  0
> AFC lock range Hz 
> AFC max drift Hz/minute 
> Enable morse decoding 
> Max no of spurs to cancel 
> Spur timeconstant (0.1sek) 
> First mixer bandwidth reduction in powers of 2 
> First mixer no of channels 
> Baseband storage time (s) 
> Output delay margin (0.1sek) 
> Output sampling speed (Hz) 
> Default output mode 
> Audio expander exponent 
> A/D speed 
> Check 
> You can carefully make a par_test file for mode "F", or make a par_wcw
> file maybe for mode "A", etc. That may get you started. If the files
> aren't made just right, they will not work.
What "just right" mean? How can it be found?
> For starters, cut the A/D speed, or reduce the powers of sine, and/or
> broaden the FFT bin size, and/or turn off AFC to reduce CPU
> requirements. I am sure others will give you better information in this
> regard. I've always had fast computer and so haven't really learned
> what must be changed to speed things up.
I have run linrad on a pentium 200 sometime ago without problems. It is
very unlikely that a P3 1.2 GHz cannot provide enough CPU power. For a
sampling rate of 8 kHz, the CPU load should very low.
I have written applications using heavy FFT and sampling at 44.1 kHz on
the same machine without problems.
> 3. Did you really try EVERY combination of parameters on the page?
> If not it would be helpful to know what you did try so we can figure out
> where things are wrong.
No, of course not. What I've tried was to get low values and change them
up a in steps. If I have to try every value, than that is something the
computer should do, not me :-). The paramenters I played the most ware the
1st FFT bandwidth (400, 350, 200, ..., 5, 0 ) and the FFT window (0, 1, 2,
..., 9). I turned off the second FFT.
> And then there is always the possibility that the error has nothing to
> do with anything I said, but that it is a symptom of an audio driver or
> other problem.
May be. In my experience, there are lots of sound applications that makes
use of some parameters that are not supported by many sound drivers. But
since I have run linrad (two years ago) on few different type of
soundcards, I assume it is quite mature in terms of support of different
sound drivers. I will take a look at the code and see what is actually
causing the "Too slow" messages. Again, 1.2 GHz should not be too slow for
an application that claims to work on a P60.
-- Edson, pu1jte, n1vtn, 7n4ncl