[Ffmpeg-devel] Re: JPEG-LS codec

[Kostya Shishkov]

Wed, 01 Feb 2006 03:44:45 -0500, Justin Ruggles wrote:
>I haven't tested it yet, but I have some comments.  First, let me say
>that the code is beautiful.  It's clear, simple, and well-documented.
>Also, I am SO glad you did this.
>
>The more I study lossless image encoders, the more I'm impressed with
>JPEG-LS.  There are better compressors out there, but few quite so
>simple and fast with competitive compression to match.  FFV1 looks
>pretty interesting, too.  At a glance, it looks similar to JPEG-LS, but
>with a better entropy coder.

Every decent lossless encoder looks like this: context determination,
prediction, error encoding. LOCO differs from JPEG-LS in two things:
context-based error encoding and context determination. IIRC, JPEG-LS
differs from FFV1 mostly in error encoding. The same prediction
function mid_pred() used in FFV1, JPEG-LS, LOCO and HuffYUV.
>I have implemented a LOCO encoder/decoder myself (not the JPEG stuff),
>and I have to say I like a lot of your solutions, namely to the run-mode
>stuff, which is a little tricky.
There's SPMG implementation of JPEG-LS with source code, I got it at
http://datacompression.info
And a lot of testing, swearing and testing ;)
>I haven't seen much about JPEG-LS 2.  I tried to download the spec from
>ITU and it didn't recognize my 3 free specs account anymore...oh well.
>Does anything in it look interesting or worth implementing?
More coding modes (modified Golomb and arithmetic) and visual-lossless mode.
SC29 site has this:
http://www.itscj.ipsj.or.jp/sc29/open/29view/29n3402t.doc
You can also download it as rec. ITU T.870 (ITU give you 3 free
downloads it you register, but hasn't work for me last month)