I have tried downloading mp4 videos from drop box to my desktop both individually and as a zipped file and the videos will not play in quicktime. The zipped folder does not open at all.
Hi,
There might be number of reasons why QuickTime is not playing your mp4 files. But the main reason i believe is unsupported codec used in your MP4.
First of all, MP4 is just a container with packaged video and audio streams that can be encoded with number of different codecs. And Apple's QuickTime supports only certain video and audio codecs in your MP4 format. If your mp4 file has unsupported codecs QuickTime will not play it.
I'd recommend you to use VLC Media Player (https://www.videolan.org/vlc/index.html) or K-Lite codec pack that comes with Media Player Classic (https://www.codecguide.com/download_kl.htm). Both of them are free, constantly updated and support virtually all existing video and audio codecs.
This worked, but I no idea why. If I use Finder and go to Dropbox most all video, show as not playable, but the data are there. I also found that trying to copy from Dropbox and paste on my desktop did not work. I then used the Dropbox app, and though I only tried it for a few videos, it worked. Why????
I just used the desktop app to sync a folder of videos and I'd say 75% of them did not work after syncing to desktop. I downloaded one directly and it worked.
Comparing the two, I noticed that the working one had the following in More Info (when I used command-I to get info.)
Codec: AAC, mp4
Dimensions: 1800x900
The broken media files do not have any codec, dimensions, duration or color profile stuff.
Dropbox: why are my files that sync via the app not retaining those pieces of data?