bytedeco/javacv

FFmpegFrameGrabber should throw an exception when attempting to access stream metadata before calling start()

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#2,382 opened on Feb 19, 2026

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Description

As stated in the title, when using FFmpegFrameGrabber, if start() is not called beforehand, methods such as getImageWidth() will return 0. This behavior may cause errors to propagate downstream and lead to issues that are more difficult to trace. I believe an IllegalStateException should be thrown immediately to clearly indicate that this operation is invalid.

Contributor guide

Research direction
Inspect the FFmpegFrameGrabber class and add an IllegalStateException to methods that require start() to be called first.
Tech stack
java
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80