[PD] Strange problem with vline~

[julien.breval at tremplin-utc.net]

Selon Carlos Pita <carlosjosepita at yahoo.com.ar>:

> [ bang ( ------[ 0 0 0, 1 15 0 (
>    |              |
>    |           [ vline~ ]
>    |              |
>    ------------[ tabwrite~ t ]

First thing, here, the order of the two actions (starting the line, starting to
record) is important: if you start the recording after the signal starts, the
beginning of the signal can't be recorded ... 
If you connect a bang to several objects, you can't really know in which order
these objects will receive the bang (normally, first connected -> first sent,
but it's not good to use this for programming)

the [trigger] object should help
for example [t b b f] has 3 outlets and sends
1. first, a float in the right outlet 
2. then, a bang in the middle outlet
3. finally, a bang in the left outlet

1, 2 and 3 are done "at the same time" (I mean, you won't hear / see the delay),
but in this specific order

for recording with tabread~, maybe you should start the recording first and then
play the signal (vline) you want to record:

[bang(
 |
[t b b]
 |    |
 |     ------------
 |                 |
[0 0 0, 1 15 0(    |
 |                 |
[ vline~ ]         |
 |                 |
  -----------------|    
                  [tabwrite~ t]



what do you mean by block size ? the pd software block size (default 64, resized
by block~ or switch~) or the sound card I/O buffer size ?

writing accurately _very_ short portions of signal is often quite difficult in pd;
sometimes, using [tabreceive~]/[tabsend~]/[bang~] is good if your recordings
have to be synchronized with the pd dsp scheduler;


don't know if it helps ... try the [t b b] thing first before

cheers,
-j

> I have this simple patch above with
> a [bang( which triggers a couple
> of messages describing a line
> segment ranging from 0 to 1 in 15 ms,
> and at the same time the writing
> of this segment into table t.
> Suppose a typical setting with
> sample rate=44100, table size=1024.
> If block size is small enough (~64 or
> less) the patch works ok. But with
> bigger block sizes the segment
> appears displaced to the right of
> the table left border as
> if its starting time was out of
> sync. Stranger yet, cause it
> starts in different positions
> of the table every time I press
> the [bang(. As I increment
> block size the average offset
> increases too. Is this a expected
> behaviour of [vline~]? Am I making
> some mistake? I understand that
> [vline] schedules its segments
> at "audio time", in other words
> that it has sample-precision
> instead of block-precision.
> Thank you in advance.
> Regards,
> Carlos
> 
> 
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