My memory isn't what it used to be, but it seems to me that I converted some MOV files to MP4 just a couple of days ago. Why does it happen now that when I try to do this I get the message "the source compression type is not supported". Really? What with the current deprecation of MOVs, isn't there a huge demand for converting them to MP4s? Is there something I'm doing wrong?
Saying MOV doesn't actually tell you much about that file. It's just the container that the video data is stored in, it's not the codec used to encode that data. Apple deprecated 32-bit QuickTime several years ago and Adobe followed suit. My guess is that the codec used is one of those deprecated ones. Adobe has written many of their own native encoders since then so support on 32-bit QuickTime wasn't necessary, but not all of them.