Takafumi-san --
You are correct that the 2.6 kernel performs correctly where
the 2.4 kernel in some cases did not. This is a consequence
of significant changes in the scheduler in 2.6. The former
problems were the result of a complex interaction of process
priorities between the audio and the X server. Some distros
would artificially boost the X server priorities so as to
improve responsiveness, and would thus interact with the
audio subsystem in unpredictable ways on some systems.
The fact that you were experiencing white noise crashes
before suggests that you are using a very old distribution
of the code. More recent code will not exhibit this behavior
under any circumstances.
The pyhw code is slow because the underlying set of
operations is very slow. A simple operation such as setting
the DDS, with the old hardware code, required hundreds of
writes to the parallel port. The speed of these writes is
completely dependent on the parallel port driver. In some
cases, the driver will pause for 1ms per write. Hence the
sluggishness of the code.
It should be pointed out that the Windows version exhibits
the same characteristics, but the slowness is disguised by
the fact that graphics operations are interleaved with the
hardware control, and thus the hardware operations do not
appear to be holding things up as much.
The new hardware control code, in pyhw2, is much more
efficient in both the Linux and the Windows versions. If you
like I will send you a tarball of the most recent version,
since we seem to be unable to get the SourceForge CVS to
keep in sync with our upgrades.
73
Frank
AB2KT
INOUE Takafumi wrote:
Bob,
I'm sorry that my info did not help you much. I'm using Knopix 3.7
(HDD installation). You can boot it with either kernel 2.4.X or kernel
2.6.X. I have almost always used kernel 2.4.27 with alsa 1.0.6 both of
which I configured and compiled myself. Under that environment I
experienced the problem I mentioned in the last post. When I start
jsdr program and give some commands (setting mode, frequency, etc.)
through cmdr and pyhw, I can hear amateur band siglnals fairly well.
Though CPU load is quite low if I do some operations like switching
KDE desktop or invoking some other programs the received signal is
lost and only 'loud white noise' is heard. The jsdr command is still
running but I'm afraid the program could not take samples from jack
any more.
Last night I reboot the sytem with kernel 2.6.9 (Knoppix3.7 default
kernel with alsa driver) and tried the DttSP program ... and it worked
fine! Now it does not lose signal. I have not yet understood why the
problem was solved. It may due to the scheduling policy of the kernel
or something. Next problem is the slow response of the pyhw command.
Takafumi
JI3GAB
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