QLab on macOS Tahoe 26.1?

[Ian MacColl]

Hello:

Are there any known problems using QLab on macOS 26.1?

I note Rogue Amoeba recently announced full support for Tahoe, given audio fixes in 26.1

https://weblog.rogueamoeba.com/2025/11/04/macos-26-tahoe-includes-important-audio-related-bug-fixes/

regards

Ian

[Sam Kusnetz]

Hi Ian

QLab 5 is in a sort of weird space with regards to macOS 26 Tahoe… we feel like we’ve fixed the most obvious issues, but there are still a few known bugs which we have not yet been able to fix. There’s also still an enduring sense of not yet knowing whether we’ve seen the whole playing field, as it were.

I know that’s not a very satisfying answer but it is the true answer.

My personal recommendation is to remain on Sequoia unless you have a specific need to update to Tahoe, but that is only my opinion.

If you’re using QLab 4, do not update. QLab 4 is incompatible with Tahoe.

Best

Sam

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Sam Kusnetz (he/him) | Figure 53

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[Pablo Navarro]

NO actualices!! Hay un problema MUY GRAVE en QLAB con MACOS Tahoe. Para video y proyecciónes, las señales saltan constantemente. Se queda sin señal, confunde señales, cambia de pantallas... a mitad de show y porque si. Sin explicación ni solución. Testeado con MacMini M2, MacBook Pro M1 y el nuevo MacBook Pro M5, todos fallando en el video.

Sigo hablando con los encargados de qlab, pero de momento, cero soluciones. Saludos!

[Ian MacColl]

Thanks, Sam and Pablo

[JV]

yo he hecho 3 shows con Tahoe 26.0.1 y me ha ido super!

controlando luces y corriendo video...

voy a actualizar a 26.1

[Ian MacColl]

Thanks, JV

[Matt Weber]

I have been running qlab on Tahoe, now 26.2, with no issue for basic sound and video cues.  Nothing too intensive which is why I decided to move forward with the update.  I did just recently find and report a playback issue with some multi channel audio files.  More of a corner case but something that made me adjust a setup.

Matt 

[Matt Weber]

That was misleading the playback issue was in some *video* files (pro res) with PCM multichannel audio.

[Chris Ashworth]

Hi all,

Just to confirm what Matt wrote below:

We have just learned today that macOS 26.2 has introduced a bug that is preventing some ProRes files with audio tracks from playing.

We are currently investigating this issue and we do not yet know the exact details.

Please be advised that updating to macOS 26.2 can break workspaces using certain ProRes video files.

-C

[JV]

Yes, it happened to me! I decided to return to Sequoia 15.7.3. Until boss Cris gives us the green light

[Pablo Navarro]

Hola! Sabemos cuándo estará arreglado el problema entonces? Tengo representaciónes a partir del Sábado durante todas las navidades con un archivo muy complejo de luces, sonido y video... ¿Qué formato de ProRes está afectado? ¿Qué solución puedo tener? Gracias

[Chris Ashworth]

We do not know when the problem will be fixed.

Our initial testing suggests that this is a bug in macOS 26.2 which may not be possible to work around.

So far we have seen the bug using some ProRes video files with an audio track. The bug is about decoding the audio track, not the video track. When we ask to decode the track, the macOS simply fails and returns an error.

We have seen it in a 2 channel and a 6 channel file, but we don’t know what specifically leads to the file being unable to be decoded.

We will continue to try to determine what specific situation leads to the issue, and I expect we will file a bug report with Apple.

-C

[Matt Weber]

To share with the group the easy workaround was to transcode the file to use AAC audio instead of PCM.  While this required remapping the audio channels in the levels tab it was not a show stopper.  The remapping was only required because the channel layout differed from what I have been using and have configured in the soundboard.  Additionally, this only impacted files with >2 channels for me.  A stereo LR track worked fine in my testing but sounds like some issues were found so YMMV.  I'm guessing there are not many people using pro res PCM with >2 channels :-)    If only compressor had more channel layouts available in the AAC options (at least I didn't see them).  I really like keeping LR as the first 2 channels in the mapping.

Matt

[Pablo Navarro]

Hola de nuevo, gracias por responder. Y, ¿habéis probado si en la beta pública de MacOs 26.3 sigue ocurriendo el problema? Porque si ahí no ocurre, una solución rápida para los usuarios que tenemos macOS 26.2 sería instalar esa beta pública. Gracias!

[JV]

Si Pablo,  a mi me todo Downgrade de Tahoe 26.3 a  Sequoia 15.7.3, no corrian los videos, ni el audio, a veces si corrian, otras veces se iba la imagen, otras el sonido, un caos total... 

[Chris Ashworth]

Yes, the problem still occurs in macOS 26.3 beta.

We have identified a work-around that we are currently testing; we will likely share a beta build here once it is ready to test.

We will also be filing a bug report with Apple.

-C

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[Chris Ashworth]

Update: 

This is NOT specific to ProRes; we have tested an H.264 file that is also affected.

The bug appears to be something specific to how audio tracks are encoded, but only when attempting to open them from video files.

We are still testing a solution that appears to work around this macOS bug; we will share it here when it is ready for testing.

[Pablo Navarro]

oh vaya... pero me alegra mucho leer que habéis encontrado la solución. ¿Cuándo saldrá la versión sin problemas? Tengo espectáculos desde mañana, todas las navidades... Gracias por el esfuerzo, ya me decís. Saludos!

[Matt Weber]

Interesting that it is not specific to pro res.  I was able to test other audio encodings and found that FLAC works and has the channel mapping I prefer.  This seems to work fine but for playback optimization PCM is lower load so this may be preferable but may not be a big enough processing load for FLAC decode to make a difference.  

I started transcoding MP4 to pro res proxy/pcm after I had mp4 playback issues (stutter/sync).  Granted that was on QLab 4 with an older Intel machine but once I find a combination that's reliable I stick with it.

Impressive you have a potential work around this quick.

Matt  

[Chris Ashworth]

Hi Matt and everyone,

Here is a beta build that we would love for you to test:

https://qlab.app/temp/QLab-5.5.9-b1.dmg 

We believe this build works around a bug in macOS 26.2 that can cause playback to fail on some video files that contain an audio track.

For macOS earlier than 26.2, this beta uses the exact same code path we used before.

For macOS 26.2 and later, this beta uses an alternate API from AVFoundation to read the audio tracks of video files. This alternate API does not appear to be affected by the regression in 26.2.

We have tested a lot of files trying to spot the pattern, but so far we don’t know what specifically causes audio tracks to fail in 26.2. However, for every file we’ve seen that does fail, this new beta has been able to read the file.

We would greatly appreciate feedback from anyone who has the chance to test this build against as many video files as possible.

Thank you!

-Chris

[Matt Weber]

I ran tests with various encodings Pro Res proxy with Flac, PCM and AAC also H.264 with the same formats.  I ran several short files plus on 75 minute file and let it play through the Pro Res PCM version.  I noticed no issue.s

The only strangeness I found was that QLab would hang for close to a minute (beach ball)  when dropping the 75 minute H.264/PCM file into the workspace for one workspace.  It did appear to play correctly after waiting for QLab to respond.  This only occured in the one specific workspace and did not happen with a fresh workspace or another recent workspace used for video.  It did exhibit the same behavior in both 5.5.8 and 5.5.9b1.  I have not been able to isolate what in the one workspace is triggering the hang.

Matt 

[Chris Ashworth]

Thank you Matt!

We’ve gone ahead and pushed this fix out in the official 5.5.9 release (now available) to get the fix out quickly.

Best,

Chris

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