grokjpeg2000enc/grokjpeg2000dec: develop plugin for Grok JPEG 2000 codec

Submitted by Aaron Boxer

Link to original bug (#785269)

Description

Grok is an open source JPEG 2000 codec, licensed under the AGPL

https://github.com/GrokImageCompression/grok

The API is currently a super-set of the OpenJPEG API, and is currently a drop-in replacement for OpenJPEG. It currently works with the openjpegenc/openjpegdec plugins.

I am planning on adding asynchronous encode/decode to make better use of multi-core. So, the library will need its own plugin.

The plugin itself will be licensed under the LGPL, following the guidelines here:

https://gstreamer.freedesktop.org/documentation/licensing.html