Hi list; thanks for a wonderful PdCon (to Stevens and NYU people especially).
I had a quick chat with Miller after the "future of Pd" discussion. I told him there is one feature I've heard Pd users ask for many times: a "clear" method for [delwrite~]. A [delwrite~] resize method is something I've heard brought up a number of times as well, but I didn't mention it.
Each of these has a runtime cost that could disrupt the realtime dsp calculation. Clearing a [delwrite~] is a linear-time operation, and for long delay lines it could cause audio dropouts; resizing is more problematic because it's not clear what to do with samples already in the delay line – probably it would need to be cleared as well, which would take even more time (although there is already an indirect resize function when sample rate is changed).
On the other hand, Pd arrays can be resized and cleared (const 0) ad libitum, which is more or less the same operation. We usually tell users 'do this at your own risk when computing audio.'
So what is the main difference? I think it's that [delwrite~] is a tilde object that is supposed not to cause dropouts on its own. If clearing it could cause a dropout, there are reasons for thinking of that as a bug rather than simply a risk.
Is there a compromise procedure? We could add an option to spread the clearing out over time. For instance "clear 5000" would mean "clear the delay line over the next 5000 ms." A second argument would let the user choose whether to preferentially preserve the most recent samples or the oldest samples. Given only a time argument, default would be to preserve oldest samples (less work has to be done overall since the write pointer would also be filling the line with zeroes). Without a time argument (i.e. "clear" with no arguments), the default would be to clear it immediately with the understanding that there could be a possible dropout.
A broader topic for another time would be "what Pd operations are/should be realtime, and which are best at load time?"
Thoughts?
Matt