Re: [linux-audio-user] why this works now ...

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Subject: Re: [linux-audio-user] why this works now ...
From: Lee Revell (
Date: Fri Sep 10 2004 - 07:42:24 EEST

On Thu, 2004-09-09 at 23:29, Eric Dantan Rzewnicki wrote:
> Well, now that I know ecasound's rtnull is not meant for use with the
> kind of thing I was trying to do and remembered that you can't add a
> chainop to 2 chains at once ... This whole thing works in one ecasound
> instance, with or without jack ... I feel really foolish for making all
> this noise on the lists all week ... <hangs head in shame> I'll try to
> write up something for the ecasound docs to explain this so others don't
> make the same mistake.

Eh, this is how free software works, the concept of wasting people's
time doesn't mean a lot. I spent a month banging my head against the
emu10k1 ALSA driver trying to figure out why the latency was 10 times
worse than in windows. Over a period of weeks I posted 5 or 6 crazy
theories to alsa-devel, all wrong. Turns out it was just a stupid bug
where a bunch of instances of SND_PCM_PERIOD_SIZE needed to be changed
to SND_PCM_PERIOD_BYTES. I submitted a patch and now the latency is
better than on Windows.

Moral of the story: in free software, the only person whose time you can
waste is your own, and it's only wasted time if you don't learn

> The upside is we have another positive experience with the patched 2.6
> kernel to report. And for myself, I'm finally using this controller I
> bought almost a year ago to have some fun making sounds. I can go ahead
> and write my randomized ECI versions as well. I'll also look into adding
> interpolation to the analogueOsc Hz control.

This is very, very important, and also very good news! There have not
been a lot of reports yet from real linux audio users. So far UP users
seem to be reporting very good results, while SMP/HT users are still
seeing weird behavior.

Can you please try the following so I can report the results to Ingo:

    Run "echo 0 > /proc/sys/kernel/preempt_max_latency"
    Do some audio work for while
    Copy /proc/latency_trace to a file and send it to me via private mail

Also, once your system seems to be running well, you should disable
latency tracing with "echo 0 > /proc/sys/kernel/trace_enabled". The
latency tracer itself can generates latencies of a few ms when it
updates /proc/latency_trace; this is not reported in the traces.



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