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Consider the following MP4 audio file, with the following codec information (Cmd+I in VLC):
VLC Media Information

When I open this file with QuickTime, or QuickLook, this file does not play with audio. However, when I open the file with VLC, the audio plays flawlessly.

When I convert the video file with FFmpeg, to a .mov file, by using the following command:

ffmeg -i file.mp4 output.mov

the .mov file has the following codec information (Cmd+I in VLC):
mov file codec information (image)

Please note that both the original .mp4 file and the new .mov file both use MPEG AAC Audio. When I open the .mov file with QuickTime, the audio now works perfectly.

These files are .mp4 files that are exported from my dashcam (Garmin Dashcam 55). I guess I could convert every file to a .mov file before storing them, but I would just like to be able to use the .mp4 files.

What is going wrong here? What am I missing? Do I need to install additional codecs on my Mac (macOS 10.14.5, nothing extra installed like Perian or whatever, just QuickTime and Final Cut Pro from the MAS)...? Why are the .mp4 files not playing with audio in QuickTime, but they are playing with audio in VLC (I know VLC has its codecs embedded in the .app itself)? Why is the .mov playing with audio in QuickTime even though it uses the same audio codec as the .mp4 file?

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  • I had to look up the tx3g codec, I've never encoded with it. Perhaps QT can't handle it? Can you use the ffmpeg "copy" stream feature to copy your 1st 2 streams (video and AAC), dropping the subtitle (?) stream? QT might be able to play that, which will tell you that it's just that 3rd stream.
    – jimtut
    Commented Jul 8, 2019 at 3:26
  • Yeah if you could narrow down which audio stream contains the actual data (and, if possible, post the offending file), it'd be much appreciated.
    – JMY1000
    Commented Jul 8, 2019 at 8:00
  • Hi guys, thank you for the replies. The videos files are copied straight from my Garmin Dashcam 55's SD card onto my internal drive. This is an example of such a file: dropbox.com/s/ukbvem4u48brkwe/GRMS0017.mp4?dl=0 The audio in VLC plays perfectly but it does not play in QT. Thank you for the help!
    – brtdv
    Commented Jul 25, 2019 at 14:06
  • if this video was still available I'd take a look!
    – Chris
    Commented Mar 9, 2020 at 22:01

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