Choosing an appropriate compression scheme for data transfer over JSON

Question

After some comments by David, I've decided to revise my question. The original question can be found below as well as the newly revised question. I'm leaving the original question simply to have a history as to why this question was started.

Original Question (Setting LZMA properties for jslzma)

I've got some large json files I need to transfer with ajax. I'm currently using jQuery and $.getJSON(). I'd like to use the jslzma library to decompress the files upon receiving them. Currently, I'm using django with the pylzma library to compress the files.

The only problem is that there's a lack of documentation for the jslzma library. There is some, but not enough. So I have two questions about how to use the library.

It gives this as an example:

LZMA.decompress(properties, inStream, outStream, outSize);

I know how to set the inStream and outStream variables, but not the properties or the outSize. So can anyone give an example(s) on how to set the properties variable (ie. what's expected) and how to calculate the outSize...

Thanks.

Edit #1 (Revised Question)

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I'm looking for a compression scheme that lends itself to highly repeatable data using python (django) and javascript.

The data being transferred contains elevation measurements. Each file has 1200x1200 data points, which equates to about 2.75MB in it's raw binary form uncompressed. JSON balloons it to between 5-6MB. I've also looked into base64 (just to cover all the bases), which would reduce the size but I haven't had any success reading it in js. I think the data lends itself to easy compression just because of the highly repeatable data values. For example, one file only has 83 unique elevation values to describe 1440000 data points.

I just haven't had much luck, mainly because I'm just starting to learn JavaScript.

So can anyone suggest a compression scheme for this type of data? The goal is to minimize the transfer time by reducing the size for the data.

Thanks.

Answer 1

For what it's worth LZMA is typically very slow to compress as well as decompress; and thus it is more common to use bit faster compression schemes. Standard GZIP (deflate) has reasonably good balance: its compression ratio is acceptable, and its compression speed is MUCH better than that of LZMA or bzip2. Also: most web servers and clients support automatic handling of gzip compression, which makes it even more convenient to use.

Answer 2

Decompression on the client side with Javacscript can take a significant longer time and highly depends on the available bandwidth of the client's box. Why not just implement a lesser but faster and easier to write decompression like rle, delta or golomb code? Or maybe you want to look into compressed Jsons?