Issues with shotcut on Mac OS Tahoe 26.0.1. Exports from mov to mp4 complete but produces a file with VERY slow audio and video. Upgraded to Shotcut 25.10.31 and tried a range of codecs and settings - resolutions, quality, hardware encorder on and off, audio sample rate, but all the same result. Libx264 codec was working perfectly until the MacOS ‘upgrade’. Mac is M3 pro 18gb ram
libx264 is independent of the OS or its version.
produces a file with VERY slow audio and video
I guess you mean like slow motion. What is the frame rate of the export file? Are you using Quicktime Player? Try playing it in Shotcut to see if it makes a difference.
Thank you. Yes it is slow motion video and audio on playback of files converted from Quicktime movie to mp4 using Shotcut with MacOS 26.0.1. The slow motion is not immediately at the start of the file. You are correct, the files recently converted after the MacOS upgrade, play fine in Shotcut and VLC but not in QuickTime. It is only these files though, previous files converted from Quicktime movie to mp4 using shotcut before macos 26.0.1 still play fine in Quicktime. The same Quicktime mov files converted to mp4 in iMovie play fine in Quicktime and VLC. I would much prefer to use shotcut, it is so much better for editing. Is there anything else I can try? Thanks
Quicktime Player has some special support for slow motion video shot with a high frame rate. It is not a bug in Shotcut. I see this from my GoPro HERO13 camera for videos > 60 fps. That is why I asked you the frame rate, which you did not provide. It did not do it before because before and now are different projects. You need to pay attention to the Video Mode in Shotcut and maybe not simply adopt the frame rate of the first video you add to the project. This can be an annoying behavior of Quicktime Player I wish I could turn off but I could not find it. The best video player for macOS is IINA.
Do a web search for “turn off quicktime player slow motion” and look at all of the complaints and confusion.
apologies, the video frame rate is 120 frames/sec in export. using libx264 Quality based VBR
Setting the export to 60 frames/sec in Shotcut fixes this problem with Quicktime playback. I am guessing the setting in Quicktime for screen capture has changed with Tahoe which is why this is now happening when Quicktime mov files are converted to mp4. Thanks for your help.