In such case, free try MacX Video Converter Pro to convert any video (5.3K GoPro, 4K, 2K, 1080p MKV) to MOV, MP4, M4V, H264, MPEG-4 QuickTime player best formats/codecs without installing any codec for QT. mov can't open on Windows 10 QuickTime QT playback staggers on large HD files (1.5GB MOV). Though QuickTime natively supports H264, MOV, ProRes videos playback, still some errors exist, e.g., Quicktime not sync audio when playing h.264 exported from adobe QuickTime error 2048 in MOV video QT won't playback audio of ProRes 422 1080p video raw. Play Any Video File on QT Needless of QuickTime Codecs

Just check out our top list of QuickTime codecs you have to download and install to expand QuickTime supported format lists, if you are subject to QuickTime video playback issues on macOS. But downloading additional codecs (e.g., MKV VP8/VP9, AV1) is deemed as indispensable to make up for the missing ones and have the videos under the compatible formats with QuickTime. QuickTime contains codecs like MPEG4, H.264, H263, DV, Apple ProRes, Pixlet, Cinepack, Motion JPEG, etc.

Quicktime player update