I am working on a compression project, and I used the default save() function in Matlab for the purpose of lossless (entropy) encoding. The transform module is all figured out.
I used the save() function to encode a 3d array that includes a bunch of zeros. I am sure that Matlab is using some kind of lossless compression with the save() function since, when I save that array, it ends up taking far less space than an array, say, containing no zeros at all. I had no success finding out what type of entropy encoding schemes are behind the function. Because it is a core part of the algorithm, I think I must at least know what is behind the function.
Plus, if you know any other type of entropy encoder that would do a better job in compressing a 3d array that contains zeros, I would really appreciate you sharing. Or, if you think I could easily write the code for that myself, then please let me know.
The v7 format uses deflate.
The v7.3 format uses the HDF5 format, which supports gzip (deflate) and szip compression. It also has an option to not compress.