[chuck-users] SndBuf causes hickup

ssalazar at CS.Princeton.EDU ssalazar at CS.Princeton.EDU
Tue Jun 12 16:35:39 EDT 2007

Hey Atte,
This is a known issue-- by default, SndBuf reads the entire file 
immediately when you specify the file path.  Due to ChucK's 
strong-timing, this will stop audio processing until the file has 
finished loading from the disk into memory, which is typically long 
enough to underflow the audio buffer and cause audible hiccuping.  
Probably the best solution is to use the .chunks parameter-- you can 
use this to load audio frames on demand instead of all at once.  E.g.

SndBuf b;
1024 => b.chunks;
"cowbell.wav" => b.read;

will specify that the file is read 1024 frames at a time when those 
frames are needed, instead of all at once.  See
for more details.  You might need to experiment with different values 
for .chunks, but that should be able to make the hiccuping go away.


Quoting Atte André Jensen <atte.jensen at gmail.com>:

> Hi
> I have (and have had for as long as I can remember) problems with
> SndBuf. I'm pretty sure the trouble is when loading a sample, then there
> will most often be a small but very noticeable hickup. It's quite bad
> with larger samples but also there with even small samples. Generally;
> the larger the sample, the greater the hickup.
> The problem seems to be gone or almost gone when the sample has already
> been loaded once, but this might be due to caching in the underlying os.
> I've tested with both alsa and jack, and all kinds of combinations of
> buffersizes and what have you, but although the problem seems the vary a
> bit (in an unpredictable pattern) it's always there. I also tested both
> syntaxes ("sample" => s.read and s.read("sample")), however only with
> wav files. I also tried both in miniAudicle and commandline chuck.
> Needless to say this makes SndBuf useless on my system :-(
> Is this a result of me doing something wrong or a bug in chuck? In any
> case is there anything I can do to remedy this right now? If it's a bug,
> I'd be most happy to help in any way I can with getting it fixed as soon
> as the developers time permits.
> BTW: This is under linux (debian/stable) on a IBM T41, 1.6Ghz, 1G ram
> and 7200 RPM HD. The system is running with a realtime patched kernel
> and is capable of playing back 20+ tracks in ardour with effects +
> various soft synths running along in realtime without a single xrun or
> glitch.
> Here's a simple example of something that shows the problem:
> http://atte.dk/download/sndbuf_test.tgz. First run shaker.ck, then after
> a while add substitution.ck (a beat => big hickup) or sd.ck (a snare
> drum => small  hickup).
> --
> peace, love & harmony
> Atte
> http://atte.dk       | http://myspace.com/attejensen
> http://anagrammer.dk | http://atte.dk/compositions
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