Monthly Archives: March 2011

Utterly Flummoxed By Arithmetic Coding

So, I’m pretty sure I understand the basic algorithm for arithmetic coding — the details may be fussy, but the overall concept is clear. But I’m completely stumped by the details of the JT version. You see, the format specifies … Continue reading

Posted in Uncategorized | 5 Comments

… and problems

Where am I now? Running what I’ve got now on the first ten TriStrip objects in the file I’m looking at gets me three simple triangle-based objects I can handle. It also gets me a bunch of — guess what? … Continue reading

Posted in Uncategorized | Leave a comment

Success!

The picture is the first TriStrip data I’ve managed to successfully read and process. I converted it to our internal mesh data structure, wrote it out as an STL file, read it into 3D-Tool, and generated the JPEG from there. … Continue reading

Posted in Uncategorized | 1 Comment

Everything I thought I knew was wrong…

Pouring over the JT 9.5 spec, trying to figure out what I might have missed that could explain the weird numbers I get, I discovered that the Int32 Probability Contexts min_value field is prescriptive rather than descriptive. That is to … Continue reading

Posted in Uncategorized | 1 Comment

What happened to Huffman?

Just decided it would make sense to check the JT 9.5 standard to see if it explained more or was somehow different. And guess what? Huffman coding has been written completely out of the spec. The CODEC types are now … Continue reading

Posted in Uncategorized | Leave a comment

Out of Band Experience

When I last left you, I was trying to figure out how to get the Vertex Data Indices to be reasonable values. In an ideal world, I’d be explaining how to do it now. In this world, though, all I’ve … Continue reading

Posted in Uncategorized | 4 Comments

Putting it Together

Well, I think I have all the bitlength and Huffman coded arrays reading in more or less correctly now. The question becomes, how do you put all these things together to make a triangle mesh? Basically at this point I’ve … Continue reading

Posted in Uncategorized | 1 Comment