[FFmpeg-devel] GP License question

[Aaron Boxer]

Hi Carl,



On Tue, Mar 22, 2016 at 11:47 AM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

> Aaron Boxer <boxerab <at> gmail.com> writes:
>
> > In fact, I couldn't find many j2k issues in trac.
>
> I see too many:
> https://trac.ffmpeg.org/query?status=!closed&keywords=~j2k
>
> > Does your codec take advantage of multiple cores?
>
> Fortunately not: Since jpeg 2000 is an intra-only codec,
> using multiple cores to decode / encode several frames at
> the same time is possible and has a significantly lower
> overhead than implementing wavefront or slice-based
> multithreaded encoding or decoding.
>
> Last time I tested the native codec was faster than
> openjpeg on a single core.
>
> > Or is it only single threaded?
>
> > Because this is one of the chief reasons for OpenJPEG
> > being slow as molasses.
>
> I don't understand: It is possible (and FFmpeg does it) to
> use multi-threading when using Openjpeg but since this is
> possible with all intra-only (and therefore all jpeg 2000)
> codecs it does not make it faster than any of its rivals.
>

JPEG 2000 supports parallelism at the code block level.
So, to decode a single frame, all code blocks can be decoded
independently. This is useful to speed up decoding a single large image.



>
> Are you interested in working on FFmpeg's jpeg2000
> implementation? If not, please consider to promote ronin
> elsewhere...
>

If I was trying to promote ronin here, I don't think I am doing a very good
job :)

I may be able to help out with FFMPeg jpeg 2000, time permitting.

Kind Regards,
Aaron