MacOS 10.15 QuickTime doesn't like variable frame rate movies?

I received an mp4 movie from a client where they had transcoded a video we created for them to add a disclaimer and also a semitransparent watermark. I believe they used ffmpeg to do this. The video plays fine in MacOS 10.12 and 10.13 but does not play well in 10.15. It's audio only after the disclaimer text. VLC is a little happier with it in 10.15.


Here's a link to one of them <https://fil.email/Law1yz4B>


mediainfo shows the file has a variable frame rate. Is this a bug in MacOS 10.15 QuickTime? I recall other forum posts here that video created with new iPhones have variable frame rates and FCPX is not happy with them, but I didn't know that QT wouldn't be happy with them either.


General
Complete name              : test2.mp4
Format                 : MPEG-4
Format profile             : Base Media
Codec ID                : isom (isom/iso2/avc1/mp41)
File size                : 22.9 MiB
Duration                : 2 min 17 s
Overall bit rate            : 1 390 kb/s
Writing application           : Lavf58.46.101

Video
ID                   : 1
Format                 : AVC
Format/Info               : Advanced Video Codec
Format profile             : Baseline@L4
Format settings             : 1 Ref Frames
Format settings, CABAC         : No
Format settings, Reference frames    : 1 frame
Format settings, GOP          : M=1, N=30
Codec ID                : avc1
Codec ID/Info              : Advanced Video Coding
Duration                : 2 min 17 s
Source duration             : 2 min 17 s
Bit rate                : 1 273 kb/s
Width                  : 1 920 pixels
Height                 : 1 080 pixels
Display aspect ratio          : 16:9
*** Frame rate mode             : Variable *** 
*** Frame rate               : 24.412 FPS *** 
*** Minimum frame rate           : 23.974 FPS *** 
*** Maximum frame rate           : 30.000 FPS *** 
*** Original frame rate           : 30.000 FPS *** 
Color space               : YUV
Chroma subsampling           : 4:2:0
Bit depth                : 8 bits
Scan type                : Progressive
Bits/(Pixel*Frame)           : 0.025
Stream size               : 20.9 MiB (92%)
Source stream size           : 20.9 MiB (92%)
mdhd_Duration              : 137886
Codec configuration box         : avcC

Audio
ID                   : 2
Format                 : AAC LC
Format/Info               : Advanced Audio Codec Low Complexity
Codec ID                : mp4a-40-2
Duration                : 2 min 17 s
Bit rate mode              : Constant
Bit rate                : 112 kb/s
Channel(s)               : 2 channels
Channel layout             : L R
Sampling rate              : 48.0 kHz
Frame rate               : 46.875 FPS (1024 SPF)
Compression mode            : Lossy
Stream size               : 1.84 MiB (8%)
Default                 : Yes
Alternate group             : 1

Posted on Jan 6, 2021 2:23 PM

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4 replies

Jan 6, 2021 5:09 PM in response to Tom Wolsky

Thanks Tom. Yes, that's the VLC behavior I also see in 10.15.


It seems our client has somehow created a strangely broken mp4. My guess is that their disclaimer text movie was created at 30FPS and they prepended it to the 23.98FPS program. Odd that older MacOS versions are fine with it, but recent and current ones choke on it.

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MacOS 10.15 QuickTime doesn't like variable frame rate movies?

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