One problem with the attached plug-in

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One problem with the attached plug-in

David R. Sky
Hi,

I have one problem with the attached plug-in I've been working on
for some time, Audio Chunker. it breaks an audio selection into
user-defined number of equal duration chunks, and moves those
chunks in time. Think of the beginning of each of those chunks as
being on a virtual spring, which can be extended so the chunks are
separated from each other by a duration of 1 chunk (shift time is
100%); lined up one after the other like the original selection
(0%); all starting at the same time, overlapping (-100%), and so on
down to -300%, at which point the last chunk from the original
selection is now the first chunk, with all chunks separated from
each other by 1 chunk duration of silence. Integer values from -300
to +100%, inclusive.

The problem is that when shift values become negative, there is
silence appended to the end of chunk audio. for instance, with a 4-
second sound broken into 4 chunks and a -200% shift, the resulting
audio is not only 4 seconds of audio, but 7 seconds: four chunks of
1 second duration, with 3 seconds unwanted silence appended after
that.

I've tried several things, including applying an extract-abs
function to the result (which I have commented out), but that
doesn't work either (with several equations to calculate the
resulting end or cutoff time). Besides which, I think if I need to
do that, I've done something inaccurate inside the make-chunk
function.

apart from the appended silence problem with negative shift values,
the audio chunks results are fine.

The code may look messy: while I'm writing code, I mark closing
parentheses so it's much easier for me to fix code, after which I
clean it up.

Thanks

David

chunker.ny (5K) Download Attachment
rbd
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RE: One problem with the attached plug-in

rbd
David,
        Nyquist is a compromise between (1) a very pure semantics where
timing is always explicit and (2) the realities of causality, finite memory,
and other implementation issues.
        As a result, Nyquist makes some assumptions, e.g. sounds do not have
negative lengths, and each sound in a sequence begins after the previous
sound in the sequence.
        I suspect your code to allow chunks to play in reverse order
violates some assumption in Nyquist. Perhaps Nyquist should be testing and
reporting when this happens.
        Can you send me the code? Attachments show up in Audacity-nyquist
digest as BASE64 binaries rather than text, and my mail reader (Outlook)
does not know how to decode this. I'm sure I could manually cut, paste, and
decode, but time is short.
        In the future, can we post either URLs or put code text in the
message bodies?

        Thanks,
        Roger




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Re: RE: One problem with the attached plug-in

David R. Sky
Hi Roger,

thanks, that's a great idea for figuring out any future Nyquist
problems! http://www.shellworld.net/~davidsky/chunker.htm has
chunker.ny, chunker.mp3 original four-second audio, and 4 example
mp3 files of what results. Further explanations are on that page.

You can receive attachments in plain text in digests if you want.
Go to the Audacity nyquist subscription page
http://lists.sourceforge.net/lists/listinfo/audacity-nyquist ,
search for 'edit options' where you type in your email address,
then click on 'edit options'. Select 'plain text' instead of 'MIME
attachments' for digests (or something like that) from that page.

Thanks very much!. David



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