Jovian Logic VI

From Just Solve the File Format Problem
Jump to: navigation, search
File Format
Name Jovian Logic VI
Extension(s) .vi
Released ≤1988

Jovian Logic VI (or Jovian VI) is a raster image format associated with Jovian Logic video capture boards (maybe the "VIA" models in particular?). It is difficult to find any authoritative information about it.

It appears to be a relatively simple uncompressed format, with a 16-byte header. It supports truecolor, grayscale, and paletted images.


Files apparently begin with the ASCII signature "VI".

Format details

This information is based on reverse engineering and guesswork. It may not be correct.

Multi-byte integers are little-endian. Offsets are in bytes, from the beginning of the file.

Offset Length Field Details
0 2 signature Always 0x56 0x49 (ASCII "VI")
2 1 image_type

0x10 = RGB, 16 bits/pixel (R5-G6-B5)
0x11 = RGB, 24 bits/pixel
0x20 = grayscale, 4 bits/pixel
0x21 = grayscale, 6 bits/pixel
0x22 = grayscale, 8 bits/pixel
0x23 = grayscale, 1 bit/pixel
0x30 = palette color, 8 bits/pixel
0x31 = palette color, 4 bits/pixel

3 2 width Image width in pixels
5 2 height Image height in pixels
7 2  ? Unknown purpose. Can be 0.
9 1 pal_code

0 = Palette entries have 6 bits/sample (18-bit color)
nonzero = Palette entries have 8 bits/sample (24-bit color)

10 1 pal_first_index Index of the first palette entry stored in the file (typically 0)
11 1 pal_length Number of palette entries stored in the file. 0 means 256.
12 2 pal_offset Offset of the palette data
14 2 image_offset Offset of the image data
pal_offset pal_length×3 palette_data Only present for paletted images.
image_offset image_data Pixels are in left-to-right, top-to-bottom order. Rows are padded to the next byte boundary.


Personal tools