AUM Audio Glitches when removing AUv3 plugins - reporting a discovery and a work-around!

andrevjunqueira

First, congratulations to @j_liljedahl for this amazing app! The brain of my iPad music operation!

I would like to share a discovery about AUM audio behavior I had today:

Since my iOS music discovery in 2018, using AUM from all my audio and music productions (live improvisations) I have always found strange every time I tried to load or unload an AUv3 plugin a small glitch in the audio happens - like plugging or unplugging a real audio jack from an amplifier or audio mixer - a "pop".

And watching Youtube video from other AUM users, with a lot of loading and removing of AUv3 plugins those "pops" never happen - a clean audio stream, even on a heavy DSP an CPU project.

And I have this "pops" even with my old 4th gen iPad - now my main device is an 8th gen iPad on iPadOS 15.1 - with any sound output device (USB interfaces, wired headphones, bluetooth headphones) any sample rates and buffer sizes.

Today with time to spare I sat down to try to figure out what was causing this: set a small test project (attached to this message) with some synths to produce sound and my usual master bus receiving audio on bus H, with the also usual AUM Peak Limiter plugin in a Pre fader FX slot, to avoid any digital audio clipping on the output. On each synth channel I loaded AUv3 in real time (internal AUM AUv3s or other) and latter removed one by one. And the "pops" happened on removal on some ocasions - like I aways had to this day.

Then I removed the peak Limiter from the master bus and VOILA! No more "pops" when removing AUv3 from the other channels!!

It seems something about lookahead limiters and AUM - this behavior was also confirmed on others AUv3 lookahead limiters I have like the IK Mixbus Limiter.

Now I have glitch and pop free AUv3 insertion and removal !

Below a video showing the before and after behaiviour and an AUM test project attached.

Hope I have helped others with similar problems. :-)

AUM test project file
https://drive.google.com/file/d/1lR0QaN28zwd2dQRzaSxZHKb87gCS1fsw/view?usp=drivesdk

Poppadocrock

I get some occasional glitches as well. Not necessarily from adding internal FX, like you displayed, but sometimes when opening the UI of an app, that’s already loaded, while the transport is running. They do seem to happen to me more often over the last 4-6 months, then ever before, but I chalked it up to my aging device, iPad 6 (2018). Sessions that are relatively small, compared to say a year ago, sometimes cause higher cpu spikes and audio glitches then they used to.

j_liljedahl

@andrevjunqueira said:
First, congratulations to @j_liljedahl for this amazing app! The brain of my iPad music operation!

I would like to share a discovery about AUM audio behavior I had today:

Since my iOS music discovery in 2018, using AUM from all my audio and music productions (live improvisations) I have always found strange every time I tried to load or unload an AUv3 plugin a small glitch in the audio happens - like plugging or unplugging a real audio jack from an amplifier or audio mixer - a "pop".

And watching Youtube video from other AUM users, with a lot of loading and removing of AUv3 plugins those "pops" never happen - a clean audio stream, even on a heavy DSP an CPU project.

And I have this "pops" even with my old 4th gen iPad - now my main device is an 8th gen iPad on iPadOS 15.1 - with any sound output device (USB interfaces, wired headphones, bluetooth headphones) any sample rates and buffer sizes.

Today with time to spare I sat down to try to figure out what was causing this: set a small test project (attached to this message) with some synths to produce sound and my usual master bus receiving audio on bus H, with the also usual AUM Peak Limiter plugin in a Pre fader FX slot, to avoid any digital audio clipping on the output. On each synth channel I loaded AUv3 in real time (internal AUM AUv3s or other) and latter removed one by one. And the "pops" happened on removal on some ocasions - like I aways had to this day.

Then I removed the peak Limiter from the master bus and VOILA! No more "pops" when removing AUv3 from the other channels!!

It seems something about lookahead limiters and AUM - this behavior was also confirmed on others AUv3 lookahead limiters I have like the IK Mixbus Limiter.

Now I have glitch and pop free AUv3 insertion and removal !

Below a video showing the before and after behaiviour and an AUM test project attached.

Hope I have helped others with similar problems. :-)

Thanks for the report! When nodes are inserted/removed, AUM re-calculates the latency compensation. If that compensation was already 0 and stays 0, it should not be audible at all. When the compensation does change (as it does when you change the Attack time of the lookahead limiter) there are clicks as the compensation delay is changed. But in your demonstration, we see that even though the non-zero latency compensation does not change, a small click/pop is heard sometimes when AUM recalculates the compensation. I'll look into this and try to get it fixed!

@Poppadocrock said:
I get some occasional glitches as well. Not necessarily from adding internal FX, like you displayed, but sometimes when opening the UI of an app, that’s already loaded, while the transport is running. They do seem to happen to me more often over the last 4-6 months, then ever before, but I chalked it up to my aging device, iPad 6 (2018). Sessions that are relatively small, compared to say a year ago, sometimes cause higher cpu spikes and audio glitches then they used to.

The glitches you describe are from DSP overload (not related to the above) in some cases caused by badly written plugins where stuff like opening/closing the UI interferes with the audio thread performance (for example by not using realtime safe lock-free data structures).