[FFmpeg-devel] Add support for j2ki/mxf

[Matthieu Bouron]

On Thu, Jul 23, 2015 at 11:04 AM, tim nicholson <
nichot20-at-yahoo.com at ffmpeg.org> wrote:

> On 22/07/15 14:29, Matthieu Bouron wrote:
> > Hello there,
> >
> > The following patchset add support for j2ki/mxf files (which store frames
> > using the separate fields / segmented frame layouts, ie: fields are
> > stored in seperate frames) through the insertion of filters at the
> > ffmpeg/ffplay level. It differs from my original attempt which introduced
> > modifications at the decoder level, which in my opinion was wrong and
> > introduced several limitations, such as:
> >
> > [..]
>
> I may be missing something here, as my mind has been on other things.
> But currently most mxf material I see that ffmpeg correctly handles is
> "frame wrapped" with the frame layout as type 1 (SEPARATE_FIELDS).
>

Can you provide samples with this layout ? I might have misinterpreted the
MXF
specs on this one. My understating is that, separated fields (as well as
segmented frame) means
that the fields are stored in a different "packet" (that might no be the
right world for it).

Also it might be specific to jpeg2000 (see below), i'll have to look again
at the mxf/jpeg2000 spec again.


>
> AFAIK these do not use filter insertion etc to work.
> Are these therefore handled at the decoder level, in which case:-
>

> a: they will not benefit from doing things at the format level.
>
> b: J2K will be an exception to the current way of doing things, which
> could add confusion.
>

It might be a jpeg2000 exception and my code will only insert the right
filters for the jpeg2000 codec.


>
> If they are not currently handled at the decoder level, the surely the
> format level must already handle this material correctly so why is your
> patch needed in this form?
>

This kind of file is not handled correctly by ffmpeg at the moment as each
field is stored in a separate jpeg2000 image.
You can find a sample attached to this bug
https://trac.ffmpeg.org/ticket/1102

Matthieu