{"id":193,"date":"2006-01-24T08:21:18","date_gmt":"2006-01-24T16:21:18","guid":{"rendered":"http:\/\/multimedia.cx\/eggs\/?p=193"},"modified":"2006-08-25T10:12:54","modified_gmt":"2006-08-25T17:12:54","slug":"8088-corruption-data-format","status":"publish","type":"post","link":"https:\/\/multimedia.cx\/eggs\/8088-corruption-data-format\/","title":{"rendered":"8088 Corruption Data Format"},"content":{"rendered":"

By now, Trixter is gaining more fame due to his 8088 Corruption video<\/a> thanks to a Digg mention. Since Alex more or less dared me<\/a> to create Unix playback software for this format I downloaded the package and examined the 8088_COR.DAT file. It’s pretty straightforward: There are 0x7D0 bytes before the start of what looks like unsigned, 8-bit PCM data (you can tell because it is all 0x80 values, silence on a scale of 0x00..0xFF). There are 0x2DF PCM bytes before the non-PCM bytes start up again.<\/p>\n

Let’s look at these numbers: 0x2DF = 735. I recognize this thanks to the Wing Commander III MVE<\/a> format. 735 happens to be the quotient of 22050\/30. The 8088 Corruption page mentions 30 frames\/second in the first place.<\/p>\n

What about the 0x7D0 number? That’s an even 2000 in decimal. 2000 = 80 x 25, the size of the standard text mode, in cells, of the old IBM 8088 machines. However, the first frame is entirely a sequence of 0xDB 0x10 byte pairs. My guess is that the video is actually using 40×25 text mode which makes for 1000 cells. Each cell is represented by an attribute byte (defines foreground color, background color, and flashing) and the actual extended ASCII character (0..255).<\/p>\n

This strikes me as a classic vector quantizer problem– all the brainpower\/horsepower goes into the compression side; the decompression is trivial. I can understand why Trixter claims the compressor is so complex.<\/p>\n

Anyway, you want to write a program to interpret the data file? If my guesses are correct, the video will be rendered as 40×25 8×8-pixel cells, or 320×200 pixels. Find a table of all of the ASCII characters. Find another table of all the attributes. Load 2000 bytes from the data file. Render the data based on the attribute and character tables. Load the next 735 bytes. Play them back as mono, 8-bit, unsigned PCM data. Repeat until EOF.<\/p>\n

As a means of validation, the size of a single frame should divide evenly into the total size of the Corruption data file which is 9268915 bytes. One frame is 2000 + 735 = 2735 bytes. 9268915 bytes \/ 2735 bytes\/frame = 3389 frames. 3389 frames \/ 30 frames\/sec = ~113 sec.<\/p>\n

Hey, Jim: Do I have that all correct? :)<\/p>\n

More on this topic:<\/em><\/p>\n