Since AVCHD is, for the most part, simply AVC (H.264) video with stereo AC3 audio in a transport stream (e.g., MTS) file container, the current High Sierra QTX player pre-scan now appears to be programmed to error trap files with AC3 mono, 2-channel, or stereo audio and prevent them from loading/opening.
It appears Apple may have 'upgraded' (i.e., depreciated) High Sierra AC3 support to match the Dolby software (i.e., lack of passthrough/non-multichannel) support adopted for IOS/tvOS releases. The window opens and shows the two previews, but when I click to open one I try to open an avchd file with 2 movies using QuickTime Player.
