[PD] vline~ precision, or sequentially segmented playback of a buffer

[William Brent]

Hi João,

The first thing I'm wondering is if you want each segment to have the
same number of samples.  I see that the time to scrub through each
segment is the same (181.818 ms), but then the length of segments in
samples varies.  I guess the pitch shift that happens from this isn't
a problem?

Also, it looks like not all of the boundaries in your log.txt line up.
 Starting on segment 330, there are gaps now and then:

198694 207333 181.818;
210909 219994 181.818;

That explains the phase discontinuities (at least some).  I know this
is just your abstracted problem, but maybe similar unexpected gaps
exist in your main patch?


On Sun, Mar 11, 2012 at 6:05 PM, João Pais <jmmmpais at googlemail.com> wrote:
> Hello list,
>
> continuing with a topic I started some time ago (but couldn't continue the
> discussion), I've made a simulated version of my patch to explain the
> situation. The full patch is too complex, and would need audio files to be
> sent with it.
>
> The context is as follows:
> An audio file stored in a buffer is played in small segments in a
> forward-backward sequence. Each segment is played after the previous, with
> no gaps in time or reading point. First segment goes as 0 - 8638.86, 2nd as
> 8638.86 - 17277.7, 3rd as 17277.7 - 25916.6 , etc. All segments are
> triggered at the same pace, in this case 181.818 ms. You can see all the
> segments in the [textfile].
> Ideally, the original audio file would be reproduced with no difference to
> the original - besides the playback pointer going forward-backward.
>
> But when playing back the segments, after the first initial moment with
> almost no problems (only the clicks when playback changes direction), clicks
> start to appear at each segment - from around sample 229K onwards.
>
> Since I'm using [vline~], I thought that the timing of the reading point
> related to the audio blocks wouldn't be a problem. But, if you record the
> output and look at the audio file, you'll see that the clicks come from a
> out of phase moment, and then the wave continues.
>
> My question is: am I doing something wrong with the circuit? If not, is
> there an efficient way of achieving a similar playback of a stored buffer?
>
> I hope everything is clear. The original patch is a monster, but this
> version sums up what's happening.
>
> Btw, in the original patch all the values are calculated in real time. But
> with the "recorded" version the audio sound just the same.
> The original audio file is 5m18s long. Will the be any round-up problems
> while calculating the segment coordinates to tabread4~?
>
> Thanks in advance for who has the time to read this,
>
> Joao
>
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William Brent
www.williambrent.com

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