[PD] So [bang~] can't "bang" in less than 64 blocksize, huh?

[Jonathan Wilkes]

On 03/16/2015 01:46 PM, Charles Z Henry wrote:
> This is the first time I've read the code for snapshot~ and
> vsnapshot~.  I had expected that it runs a message routine during the
> perform routine--and it does not.  You can't take the output of
> snapshot~ and use it to affect the following sample with a blocksize
> of 1.
>
> Messages are blocking, and processed depth-first as I understand it.
> That's why the infinite loop in Pd is so fatal to the process.
>
> So, what if I made an external (however dangerous to patch) that does
> trigger a float message during each perform routine?  What good is it?

It'd be something like vline~ but going in the opposite direction. But I 
think there are problems with it.  (See below.)

>
> One programming hazard:  I think with this external it would be
> possible to run things out of order, so that some messages that occur
> slightly sooner in logical time from an object like metro, wait until
> the default dac block size occurs, and wind up running after all of
> the messages that occur during the perform routines.
>
> Part of what I'm missing is how the timed messages work.  I never
> learned this completely.

[Warning: wrong things may lurk below.  I'm still figuring out how this 
works...]

They work off of clock callbacks.  clock_set registers the timestamp in 
a linked list, and before it fires the corresponding event it sets the 
current time to that timestamp.

That way even if a dsp tick were somehow changed to last an entire day, 
you could still get deterministic output out of the timing objects when 
they fire at rates shorter than a day.  For example, you could specify 
delay times for printing out a message at breakfast, lunch, and dinner time:

[loadbang]
|
[delay 8 hours]
|
[breakfast time!(
|
[print]

[loadbang]
|
[delay 12 hours]
|
[lunch time!(
|
[print]

[loadbang]
|
[delay 18 hours]
|
[dinner time!(
|
[print]

In such a case of day long system blocks, all the messages would 
unfortunately print out without any delay between them.  But on the 
bright side, the clock callback timestamps would ensure that you see 
them print out in the correct order.  Additionally stuff like [timer] 
would output a value _as_ _if_ those delay objects had fired with the 
timestamps you provided them.

Now, in that same day-long block system, from what I understand you 
could use [vline~] to have ramps (or jumps) in the signal at the 
relevant meal times.  That's one of the reasons Pd's clock API is very 
useful.  Still, there's no way I know to get events to actually fire at 
anything lower than the system block time.  At least not without doing 
your own timekeeping inside your external.

Anyway, if you make the external to output a bang inside the perform 
routine, try it at [block~ 1], and measure the logical time between 
outputs with [timer].  My prediction is that it will measure "0", which 
is wrong.  So I think you'll have to do the math inside the perform 
routine to figure out what the delay would be given a block size below 
64, and then use clock_set to output the bang with the relevant delay 
specified.

-Jonathan

>
>
>
> On Sun, Mar 15, 2015 at 11:55 AM, Jonathan Wilkes via Pd-list
> <pd-list at lists.iem.at> wrote:
>> snapshot~ is to vsnapshot~ what line~ is to vline~.
>>
>> Did you read the chapter of Miller's book which he linked to here?
>>
>>
>>
>> On Saturday, March 14, 2015 11:55 AM, Alexandre Torres Porres
>> <porres at gmail.com> wrote:
>>
>>
>> moreover, [snapshot~] will also print 64 equal values of the last value in a
>> 64 block even if the patch is running at a block size of "1", being this
>> kind of behaviour my biggest surprise that i point in this thread.
>>
>> 2015-03-14 12:17 GMT-03:00 Alexandre Torres Porres <porres at gmail.com>:
>>
>>> snapshot~ will always output the last sample from an audio block of 64
>> This sounded strange at first to me, but it makes sense if you consider
>> that snapshot~'s role is to give you one audio sample from the audio
>> stream. Since you will only receive messages in between audio blocks the
>> last sample in a vector is the one that is closest (in timing) to the
>> point at which you receive the value in the gui.
>>
>>
>> For snapshot, I know I ran proper tests as I was comparing it to vsnapshot~,
>> meaning that it wasn't constricted to the bang gui behaviour. So sending
>> bangs at every sample did only spit out 64 equal values of the last sample
>> in the block - whereas [vsnapshot~] can give a value for each sample.
>>
>> cheers
>>
>>
>>
>> 2015-03-14 12:13 GMT-03:00 Alexandre Torres Porres <porres at gmail.com>:
>>
>>> print~ will always start printing from the beginning of a 64 block period
>> The same here. Perhaps it helps to see print~ as the object that gives
>> you one audio block as numbers rather than an 'audio rate print' that
>> does things faster than message timing.
>>
>> I also meant that it can't help but start from a 64 block boundary, even if
>> the block is less, such as "1", but I think that this is because the bang
>> button is always aligned to a 64 block tick, as I pointed out later, so I
>> may have to run other tests to see how [print~] actually behaves with
>> different size blocks.
>>
>> cheers
>>
>> 2015-03-14 6:21 GMT-03:00 Peter P. <peterparker at fastmail.com>:
>>
>> * Alexandre Torres Porres <porres at gmail.com> [2015-03-14 07:36]:
>>> It seems there are other objects that somehow restrict themselves to a 64
>>> size block minimum.
>>>
>>> print~ will always start printing from the beginning of a 64 block period
>> The same here. Perhaps it helps to see print~ as the object that gives
>> you one audio block as numbers rather than an 'audio rate print' that
>> does things faster than message timing.
>>
>>> snapshot~ will always output the last sample from an audio block of 64
>> This sounded strange at first to me, but it makes sense if you consider
>> that snapshot~'s role is to give you one audio sample from the audio
>> stream. Since you will only receive messages in between audio blocks the
>> last sample in a vector is the one that is closest (in timing) to the
>> point at which you receive the value in the gui.
>>
>>
>>
>>
>>
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