ext/tarkin/WHAT_THE_HECK_IS_THIS_CODE_DOING

This is deprecated. Take a look in the w3d/docs directory.

The command line semantics are changed. You have to call the test program
now like this:

./tarkin_enc ../clips/venuscubes-ppm/AnimSpace00%03d.ppm 5000 4 4
./tarkin_dec

------------------------------------------------------------------------------

Hi,

this is a experimental 3d-integer-wavelet-video compression codec. Since the
integer wavelet transform is reversible and a reversible rgb-yuv conversion
is used (you can understand it as (1,2) integer wavelet transform, too), this
codec should be lossless if you transmit the whole bitstream.
The Y/U/V-bitstreams are embedded, thus you can simply get lossy compression 
and shape the used bandwith by cutting bitstreams, when a user defined limit 
is reached.


Here is how the current code works:

First we grab a block of N_FRAMES frames (defined in main.c) of .ppm files.
Then each pixel becomes transformed into a YUV-alike colorspace. Take a look in
yuv.c to see how it is done. Each component is then transformed into frequency
space by applying the wavelet transform in x, y and frame direction. 
The frame-direction transform is our high-order 'motion compensation'.
At boundaries we use (1,1)-Wavelets (== HAAR transform), inside the image 
(2,2)-Wavelets. (4,4)-Wavelets should be easy to add. See wavelet.c for details.

The resulting coefficients are scanned bitplane by bitplane and 
runlength-encoded. Runlengths are Huffman-compressed and written into the 
bitstreams. The bitplanes of higher-frequency scales are offset'ed to ensure a
fast transmission of high-energy-low-frequency coefficients. (coder.c)
The huffman coder is quite simple and uses a hardcoded table, this can be done
much better, but I wanted to get it working fast.

Decompression works exactly like compression but in reversed direction.

The test program writes for each frame the grabbed original image, the y/u/v
component (may look strange, since u/v can be negative and are not clamped to
the [0:255] range), the coefficients (look much more like usual wavelet 
coefficients if you add 128 to each pixel), the coefficients after they are 
runlength/huffman encoded and decoded, the y/u/v components when inverse wavelet
transform is done and the output image in .ppm format.

You can call the test program like this:

  $ ./main 20000 5000 5000 ../clips/%i.ppm

which means: images are grabbed from directory ../clips/0.ppm, ../clips/1.ppm,
etc. The Y component bitstream is limited to 20000 Bytes, the U and V bitstreams
to 5000 Bytes. If the last argument is omitted, frames are taken from current
directory.

Good Luck,

- Holger  <hwaechtler@users.sourceforge.net>