audio crackle when reading from an audio table. What am I doing wrong?

iLex · April 2023

Hi! It's been a long time since I did anything in Reaktor (besides building Racks). I am looking to create a simple rewind plugin.

Basic operation:

audio is recorded into an audio table. Settings in two screenshots attached.
whenever the 'reverse' button is pressed (which comes in at the REV input in my screenshot) the audio plays backwards from the last write position
(the REV button re triggers the top Ramp Osc, while triggering the last value of the bottom Ramp Osc)
Speed controls the rewind speed (multiplier)

Whenever I rewind with Reaktor inserted on an audio track in Logic Pro, there is a lot of crackle (digital too low buffer-size style crackle).

I've tried:

different buffer sizes
having the ensemble stop recording when rewinding
different rewind speeds

Anything I am overlooking? Does anyone know how to fix this?

Thanks in advance!

colB · April 2023

It would be easier if you posted the ensemble.

Does it work with Reaktor in stand alone mode?

iLex · April 2023

Rewinder.ens

Thank you for your reply!

Yes of course! It makes sense to add the ensemble😂

It does the same thing (arguably worse) in standalone mode.

colB · April 2023

Try putting both ramps into 'hi-res' mode.

I think what is happening is that in normal or sync mode, because the scaling is so high (x480000), a single sample tick is too small, and write sometimes skips a sample here and there... but the playback sometimes plays one of those samples that were missed.

~~I guess what 'hi-res' does is switch to 64bit processing (just guessing)~~

This is easier to analyse in core where things like 32bit vs 16bit are explicit, and you can use integers for table indices, making it easier to guarantee correct functionality.

....

If you rig this test up, it demonstrates that the difference between the current and previous indices is often greater than 1 causing the write position to skip over some table slots. When switched to high res, it is often just less than 1, and occasionally greater than 1.

IMO it would be better to build this in core. In core, you can guarantee that you always hit every index!

If not, then still better to build it using some sort of counter for the write index instead of using a ramp.

iLex · April 2023

Thank you so much for your help!

Sadly I don't have the knowledge to code something like this (or anything else) in core. I'm a composer who likes to dabble in things like this, mostly to 'program' things I need for my projects (like a 7 speaker panner and such things).

I'll try what you said, including a counter. Maybe it would also be functional if I switch to milliseconds, which at least brings the resolution back to 10.000.

I'll let you know if I figured it out!

colB · April 2023

https://community.native-instruments.com/discussion/comment/63565#Comment_63565

I'll try what you said, including a counter

Hmm, counter is tricky in Primary, because counter is not an audio rate object in primary.

Don't be scared of core, it's really not much different, and where it is different it's usually in a good way ;)

I had a quick go at a core rebuild. Maybe I'll do a mini step by step once you taken some time to try and solve it yourself. It's actually a really good project for an 'introduction to core!'

iLex · April 2023

Cool! I'll take your challenge.

See you in ehh... less than half a year I hope...

iLex · April 2023

Okay, so that was easier than I thought. A little help from a tutorial, well, a lot of help from a tutorial , and some customisation and I got my counters.

It works perfectly, no glitches!

I am kinda tempted to see if I can manage to make the table in core too. Will post here if I do.

Thanks again!