I'm tasked with inserting custom metadata that can be read back to define at timestamp X of an MP4 file obtain certain data, a key value pair lets say. 

Is Bento4 the right tool for the job? 

FFMPEG seems to only let you modify an MP4s global metadata, nothing local or at certain intervals. 
Can this be used to read and write custom metadata to an MP4 at certain timestamps? 
This is a GitHub Issue
repo:Bento4
owner:axiomatic-systems
Title : Can this be used to read and write custom metadata to an MP4 at certain timestamps? 
Issue date:

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I'm tasked with inserting custom metadata that can be read back to define at timestamp X of an MP4 file obtain certain data, a key value pair lets say. 

Is Bento4 the right tool for the job? 

FFMPEG seems to only let you modify an MP4s global metadata, nothing local or at certain intervals. 
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