[linrad] Re: Using the Linrad Network

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hello Joe,


> Today I made my first tests of Linrad's network broadcasting 
> capability.  I installed Linrad 02.34 and checked it out.  All 
> seemed to be well.  I selected "N" on the main menu to 
> initialize networking parameters, and then selected "format 4" 
> (16-bit raw data) for output.  After toggling network write ON, 
> I found that the program continued to run correctly in Weak CW mode.
Ok.

> Unfortunately, I did not have good luck with any of the other 
> data formats.  In particular, formats 7, 8, and 9 caused the 
> program to produce broken sound output -- that is, frequent gaps 
> in the Rx background noise when an active frequency is selected 
> with the mouse.
> 
> Hitting "T" while receiving, so as to display timing 
> information, shows an apparent A/D sampling rates as follows:
> 
> Format A/D
> -----------
> 4     96 kHz
> 7    ~30
> 8    ~73
> 9    ~49
> 
> Obviously, something is seriously wrong!
Yes. 

While writing this mail on my single Pentium 2.66 MHz machine,
I have one issue of Linrad running two RF channels at 96 kHz 
from the WSE units sending fft1 data to the network. I also
have two more issues of Linrad receiving the fft1 transforms.
All three issues are sending data to the loudspeakers
simultaneously. I notice no problems of any kind.
This is under Debian with kernel 2.6.18-4-686-bigmem
and oss-linux_v4.0-1002_i386.deb

When I start the system monitor I get a short break just when
the program opens. All three Linrad issues have the second FFT 
enabled and the total CPU load according to the system monitor 
is about 40% with occasional peaks up to 70%.

When I start a fourth issue of Linrad that reads 154 kHz from
an SDR-14 and also sends data (16 bit raw) to the network,
things still work fine with a total CPU load of 60% using
1.2 gigabytes of RAM. In this situation, the USB driver 
for SDR-14 crashes in case I try click on any other window
because there is not an appropriate error handeling when
data is lost from the USB device. This does not affect
the other three issues of Linrad.

It seems to me that the problems you see could be caused by
excessive RAM allocation that would cause active data areas 
of Linrad to be swapped on the hard disk. It could also
be a problem due to interrupt sharing.

I noticed a bug. In case I press T when Linrad runs from
fft1 input, the A/D rate becomes 192 kHz and an error message
is displayed. This does not affect the processing however.

> I did notice that when using Format 9, although the audio on the 
> master computer has frequent interruptions, watzo running on a 
> second computer displays waterfall data that looks more or less 
> correct.
> 
> I tried to use one instance of xlinrad to broadcast "format 4" 
> data, and a second instance of xlinrad on the same computer 
> receiving the raw 16-bit data.  This failed with error #1272 
> ("Write to network socket returned an error") on the master and 
> error #1274 ("Network read failed") on the slave.
Something is wrong. Presumably the reason is the same as for
the other errors you observe.

> Can you help me to understand what may be wrong in my setup? 
> The computer on which Linrad is running is reasonably fast (2.7 
> GHz P4, 0.5 MB cache, 1.25 GB memory), and is around 20% busy 
> when running xlinrad.
Check for memory usage first.

73

Leif

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