Wednesday, May 30, 2012

FLV Data Extractor and the Mystery Tag

I finally finished that FLV Data Extractor I mentioned in my last post. You can download a copy of it here: The program has a command line interface, but I am strongly considering writing a generic GUI that can be placed over command line programs. I imagine that many modern computer users are not even aware of the Windows console, let alone how to use it, so if you want lots of people to use a program, it should probably have a GUI. There are still merits to the command line interface. For example, you can use programs with CLIs in batch files, but I suppose even windowed programs can also support command lines for such purposes. I’ll have to play around with the generic GUI idea and see how it works out. I may just end up modifying the FLV Data Extractor to have a GUI with support for the command line too.

If you try out the program, you’ll probably notice that it asks you to agree to some terms before using it. While I distribute most of my software for free, I can’t get over the idea of someone using my software for profit. I suppose this is a personal hang-up of mine and that I should get over it, but I can’t, at least not now.

On a final note, while testing the FLV Data Extractor, I came across a strange occurrence. Adobe’s FLV format specification only mentions three types of data tags: audio (0x08), video (0x09), and script data (0x12), but in some of my files, there was another mysterious data tag, 0x0F. I tried googling for information but turned up nothing. I then examined the data included in the mysterious tag, and it seems to be like a script data tag except that there’s a mysterious 0x00 byte before the start of the event name. This mysterious tag is why I added the -u flag to the command line options. I don’t know what the mystery byte is meant to indicate. If it’s a count of some kind or if it indicates the presence of some extra data, this will cause problems with the -u flag. If you happen to find any FLV files that produce errors or unknown tags (even with -u set), feel free to send them to me for analysis.

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