FLVMeta

FLVMeta is a command line application that can help you edit FLV video files' metadata in a quick, convenient manner. It can also perform checks for file validity and dump metadata just as easily.

Portable tool

Since it is portable, you do not need to install it on the target computer, as simply unpacking the archive it comes in and launching the executable grants you full access to its functions.
More so, you can run it from removable storage media such as USB flash drives or external HDDs and not worry about it tampering with your Windows registry entries or creating additional files or folders on your PC without your explicit permission.

Command Line Interface (CLI)

FLVMeta does not feature a standard Graphic User Interface (GUI), as it provides you with a Command Line Interface instead. The lack of a GUI can be disconcerting for some users that might find it difficult to operate its controls.
However, despite this potential inconvenient, it provides you with a handy help section that can be accessed by launching the executable along with the "--help" argument.

Edit FLV metadata

You can turn to this application if you need to modify metadata for your FLV video files quickly and conveniently. In order to do so, you just need to launch the executable and attach the corresponding arguments.
The value types you can insert in the target documents include keyframe indices used to allow random access seeking or the onLastSecond event, which announces the end of playback and possibly make the video player stop. More so, it can help you dump metadata or extensive file details to your PC in various formats such as JSON, XML or YAML. Furthermore, you can check the validity of your files to prevent potential issues from occuring.

Lightweight FLV metadata injector and extractor

All in all, FLVMeta is a portable command line application that can help you inject metadata into your FLV documents with minimum efforts, but also extract it or check the file's validity. It lacks a standard GUI but provides you with a brief description of its functions by assigning the "--help" argument when launching it.