Ardour freezes for a long time after stopping playback

[lminiero]

This is probably the same as #549, which was closed at the time: I tried adding some comments a few years ago to say it was still happening to me, but since I got no response or feedback, I thought I'd create a new issue using more updated versions. As I'm writing this, it happens using Sfizz 1.2.3 on Ardour 8.2, but it has always happened to me for all the years I've been using sfizz.

It seems to be related to how many sfizz tracks I have in my Ardour project: the more there are, the more the UI freeze lasts until I'm able to interact with Ardour again. I work a lot with orchestral templates, which means I have 20-30 sfizz tracks loaded, usually, which results in very long pauses any time I pause. This is the only info I can find in the Ardour logs:

2024-03-02T16:34:27 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d667b3a0
2024-03-02T16:34:29 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d5c0d830
2024-03-02T16:34:31 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x559413902850
2024-03-02T16:34:33 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d44424b0
2024-03-02T16:34:35 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x55945fbb8a40
2024-03-02T16:34:36 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d1b65c70
2024-03-02T16:34:38 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5594105ccca0
2024-03-02T16:34:40 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593ce3e2c40
2024-03-02T16:34:41 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5594625a8fc0
2024-03-02T16:34:43 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d4febaa0
2024-03-02T16:34:45 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d8e7a760
2024-03-02T16:34:46 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x559452834f90
2024-03-02T16:34:48 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d2a05380
2024-03-02T16:34:49 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593dc519480
2024-03-02T16:34:51 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593cfe2e370
2024-03-02T16:34:53 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d7d80230
2024-03-02T16:34:54 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593cd6ec9c0
2024-03-02T16:34:56 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d7308960
2024-03-02T16:34:58 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x55945f24d1b0
2024-03-02T16:34:59 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d0d08420
2024-03-02T16:35:01 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593db31eb10
2024-03-02T16:35:03 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593d37ca920
2024-03-02T16:35:04 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593da0866a0
2024-03-02T16:35:06 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x5593cf0c4470
2024-03-02T16:35:07 [INFO]: Removing MIDI patch file custom:Sfizz LV2:0x55945a587c50

In this specific instance, 16:34:27 is when I stopped the playback, and 16:35:07 is when the UI unfroze. As you can see, that's 40 seconds of Ardour not responding, which is a lot. If I unload all sfizz instances in my tracks, stop/play is immediate, which confirms it's related to sfizz somehow.

The only workaround I've come up with was to create audio tracks associated to sfizz, so that when I consolidate some tracks, I render the related MIDI track to audio and unload its sfizz instance, but that's still quite painful to work with, especially when I'm fine tuning stuff and need to balance tracks.

Please let me know if there's any other info I can provide to help sort out the issue. Thanks!