drewnoakes/metadata-extractor

How to deal with incorrect quicktime timestamps?

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#527 opened on Feb 3, 2021

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 (5 comments) (0 reactions) (0 assignees)Java (2,411 stars) (470 forks)batch import
bugformat-movhelp wanted

Description

Per https://exiftool.org/forum/index.php?topic=7911.msg40318#msg40318:

The problem lies in the specification of the QuickTime date fields. These are 32 bit integers measuring the time in seconds since 1904, however many brain dead programs (as Phil rightly calls them) used the “unix” standard of 1970 as starting point. To cater for this (common) error, Phil decided to assume 1970 as starting point for dates before 1970 (when counting from 1904). Effectively this means exiftool, by default, does not show you the correct date for dates < 1970.

This brings up some questions:

  • Do we apply the same adjustment automatically in this library?
  • Do we document this recommended behavior in the Javadoc?
  • Do we add an option to optionally enable this behavior?

I mention this because I'm getting some MP4 timestamps returning 1946 with this library and 2012 with exiftool and I know for a fact the latter is correct. I am applying the above adjustment manually in the application layer but it took me a while to track down the cause.

Contributor guide

Tech stack
java
Domain
backenddata
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaQuickTime date handling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Examine the library's QuickTime metadata reader (likely in the 'com.drewnoakes.metadata extractor' source) for current date handling. Review the exiftool forum post referenced in the issue to understand the automatic adjustment approach. Consider implementing one of the three options: automatic adjustment, documentation update, or an optional flag to enable the Unix epoch fallback for dates before 1970.