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Think I’ve about figured out my problems with the MPEG version of Lunar.

The CD XA format has some metadata that goes along with the actual data in each sector, signalling things like “what kind of data is in this sector?” I guess the intent is that primitive systems can use the sector metadata without needing to actually identify the file type using other means?

At any rate, the “bad” version of the MPEG file is always having the “data” bit set, while the “good” version varies between “video”, “audio”, and “data”. Feels like Lunar is probably skipping over every non-video sector.

There’s also a format-dependent “coding” byte, which the “bad” tool is setting to 0. It has information about resolution and coding type; Lunar may be depending on it.

I’ll continue investigating, but I think I have all I need to attempt a fix now.

Once I get this fixed and I’ve confirmed (or disconfirmed) my investigation, I’ll put up a blog post that goes into all this in more detail!

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