[FFmpeg-devel] Support for dumping pgx for JPEG2000

[Gautam Ramakrishnan]

On Mon, Jun 22, 2020 at 11:37 PM Gautam Ramakrishnan
<gautamramk at gmail.com> wrote:
>
> On Mon, Jun 22, 2020 at 11:30 PM Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> >
> > Am Mo., 22. Juni 2020 um 19:40 Uhr schrieb Gautam Ramakrishnan
> > <gautamramk at gmail.com>:
> > >
> > > On Mon, Jun 22, 2020 at 8:07 PM Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> > > >
> > > >
> > > >
> > > > > Am 22.06.2020 um 12:42 schrieb Moritz Barsnick <barsnick at gmx.net>:
> > > > >
> > > > >> On Mon, Jun 22, 2020 at 12:47:11 +0530, Gautam Ramakrishnan wrote:
> > > > >> On Mon, Jun 22, 2020 at 12:38 PM Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> > > > >>>> Am 22.06.2020 um 07:32 schrieb Gautam Ramakrishnan <gautamramk at gmail.com>:
> > > > >>>> JPEG2000 uses .pgx format for conformance testing. Is it a good idea
> > > > >>>> to allow the ffmpeg native decoder to have an option to dump .pgx files?
> > > > >>> I believe it would be more useful if FFmpeg could read pgx files.
> > > > >> So could a new Codec be created for reading and writing pgx files?
> > > > >
> > > > > Actually, probably a very simple demuxer/muxer, as the payload seems
> > > > > to be uncompressed/raw.
> > > >
> > > > Most likely a decoder as for pnm or tga.
> >
> > > I shall work on this. The format seems really simple. However,
> > > how do I make the encoder write multiple files and the decoder
> > > read multiple files? Each component would map to one .pgx file.
> >
> > You only read one of the files at a time, the extractplanes filter can
> > be used to compare the content.
> >
> > Carl Eugen
> > _______________________________________________
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> >
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>
> So what you mean to say is if I am given say 3 pgx files for r g and b
> components respectively, the decoder would not decode all of them into
> one image. But as this is a testing format and only for conformance testing,
> that should not be an issue?
>
> --
> -------------
> Gautam |

Another issue is that as the .pgx format is tightly linked to JPEG2000,
how could the format be restricted to conversions between j2k and jp2
files only?
For example, the pgx header contains a field called signed, which
indicates whether
the component values are signed or unsigned. This seems very specific
to jpeg2000
and would not probably allow conversion from pgx to other formats directly.

-- 
-------------
Gautam |