Playback can freeze with high latency plugins

[Ryan-Miller-Audacity]

Bug description

With some high latency plugins, playback will freeze and become inoperable after performing the latency testing steps.

So far this has been confirmed with Z-Noise from Waves

https://user-images.githubusercontent.com/88568755/191254992-652cc11d-d9ae-439c-ba88-a2477acfb0ba.mp4

Waves lists their latency values for their plugins here: https://www.waves.com/support/tech-specs/plugin-latency

Steps to reproduce

1. Go to www.waves.com and register an account and get a demo license of the "Z-Noise" plugin via get demo button on that plugin's webpage: https://www.waves.com/plugins/z-noise
2. Download Waves plugin manager
3. Use Waves plugin manager to install/activate your demo license for Z-Noise
4. Open Audacity
5. Generate a rhythm track
6. Add the Z noise plugin to that track's realtime effect stack
7. Go to Tracks -> Mix -> Mix and Render to a new track
8. On the new track apply the "Invert" effect via the destructive effect dropdown
9. Click play
10. Note that playback is frozen (the play marker doesn't move) the only indicator that playback is active is the depressed play button.

Expected behavior

Playback should not freeze and function appropriately.

Actual behavior

Playback freezes.

Audacity Version

latest beta

Operating system

Windows, macOS, Linux

Additional context

No response

[DavidBailes]

I can reproduce the problem using the free voxengo latency delay plugin, using default settings: https://www.voxengo.com/product/latencydelay/

[saintmatthieu]

@dozzzzer I think this is fixed now, since @vsverchinsky implemented the master channel. Could you please verify ? Note that high-latency is still isn't properly handled, and there is another issue for that: #6519

[Paul-Licameli]

@dozzzzer I think this is fixed now, since @vsverchinsky implemented the master channel. Could you please verify ? Note that high-latency is still isn't properly handled, and there is another issue for that: #6519

#6442 if completed, reviewed, and merged will completely rewrite the handling of latency and justify re-testing.

[dozzzzer]

The original issue cannot be reproduced anymore: I experience no playhead stuttering or playback freeze with the Invert applied to the second track. However, playhead still stutters when a plugin with latency (e.g. Voxengo Latency Delay) is added to the Master channel too, and even when it's disabled, stuttering persists.

https://github.com/audacity/audacity/assets/70063970/5e3aee72-0bfe-40bc-bbde-553270679a0f

[Paul-Licameli]

I may request a re-test of this on another branch.

Watch #3651