comments on late joyrides re: rt performance

[victor]

you are absolutely right. I can use very large buffers; however there
are two things: I was using quite large ones (but not the immense ones you
quoted)
but  say 8192 samples, and I was still getting dropouts. The larger
the buffer the longer the dropouts were lasting for. Yes, I can try
with larger buffers. But in any case, the target is not the MIDI app,
that was just the test case, because it was simpler than hooking
a keyboard and playing along.

Victor

----- Original Message ----- 
From: "Benjamin M. Schwartz" <bmschwar at fas.harvard.edu>
To: "victor" <Victor.Lazzarini at nuim.ie>
Cc: <devel at lists.laptop.org>
Sent: Saturday, August 16, 2008 9:14 PM
Subject: Re: comments on late joyrides re: rt performance


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> victor wrote:
> ...
> | Comparing the RT audio performance of the two, I must say
> | I am disappointed with how worse it has got.
> ...
> | One of the things I have been playing with is a little MIDI file player
> | (one of the test/example activities in
> devel.laptop.org/activities/csndsugui),
> | which uses a soundfont synthesis engine.
>
> While diminished RT performance is a serious problem, it occurs to me that
> a properly designed MIDI file player should not require low latency at
> all.  The ALSA audio design makes it easy for applications to request long
> buffers..  For example, the Distance activity plays audio with
>
> subprocess.call(["/usr/bin/aplay", "--buffer-time=10000000", fname])
>
> to request a maximum-size buffer, precisely because of the latency issues
> that I observed in testing.  (Yes, this is incredibly ugly, but using
> gstreamer in a multithreaded python app is uglier.)
>
> Interactive sound synthesis is a different matter, but for pure playback,
> perhaps you just need a longer buffer.
>
> - --Ben
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