Duration Discrepancies

[jkellough]

First off, I'm a Noob, yup, first post! So, apologies if I'm not precise or mix up terminology.

I'm working with 1000's of spatially referenced Full Motion Video's in mp4 format. Part of my QA/QC process is to ensure the video length in seconds matches the telemetry data (csv files) by row count (i.e. 1 record per second of video).

For the vast majority of videos, I find the exiftool records for Duration, Track Duration and Media Duration to be identical as should be expected for videos of this nature. However, on occasion I have found discrepancies between these records.

For instance, I have a video when opened in VLC media player that is 0:37:51 in length however, exiftool returns Duration and Track Duration as 0:37:51 and Media Duration as 0:18:55. Realizing that Duration and Track Duration are double the Media Duration, I watched from 0:18:50 to see if the video was simply repeated - it was not. Can anyone offer an explanation why or how these three Duration records can differ? Thank you all, your help is much appreciated.

[Phil Harvey]

I think you will have to ask an MP4 expert about this one, or spend a year or more trying to understand the cryptic specification (which isn't free, btw).

I have a number of MP4 videos where the MediaDuration is vastly different from the TrackDuration.

- Phil

[StarGeek]

You might want to use FFProbe (part of FFMpeg) to look at video metadata.

[jkellough]

Thanks @Phil Harvey and @StarGeek. I did figure it out. The fact the video was exactly double its telemetry was suspect and upon comparing its framerate to adjacent spatial videos I noticed it was slowed down. Simple fix with ffmpeg and all is well now.

And now the Duration, Track Duration and Media Duration all match. Cheers!