[FFmpeg-devel] [RFC PATCH v2] libavcodec/jpeg2000_parser: Add jpeg2000 parser

[Michael Niedermayer]

On Thu, May 21, 2020 at 09:42:18PM +0200, Carl Eugen Hoyos wrote:
> Am Mi., 20. Mai 2020 um 22:21 Uhr schrieb Michael Niedermayer
> <michael at niedermayer.cc>:
> >
> > On Wed, May 20, 2020 at 08:48:41PM +0530, Gautam Ramakrishnan wrote:
> > > On Tue, Apr 21, 2020 at 3:41 AM Michael Niedermayer
> > > <michael at niedermayer.cc> wrote:
> > > >
> > > > On Mon, Apr 20, 2020 at 04:13:44PM +0530, Gautam Ramakrishnan wrote:
> > > > > On Mon, Apr 20, 2020 at 3:38 PM Michael Niedermayer
> > > > > <michael at niedermayer.cc> wrote:
> > > > > >
> > > > > > On Mon, Apr 20, 2020 at 01:36:47AM +0530, gautamramk at gmail.com wrote:
> > > > > > > From: Gautam Ramakrishnan <gautamramk at gmail.com>
> > > > > > >
> > > > > > > I have attempted to write a JPEG2000 Parser. Need
> > > > > > > help on testing the code and some tips on how to
> > > > > >
> > > > > > to test the code i would sugest to generate a file
> > > > > > or files with many jpeg2000 images and then try to
> > > > > > decode it to -f framecrc
> > > > > This helps me check whether the image is correct by comparing the CRC value?
> > > > > > if that work repeat while varying the packet size
> > > > > > input to the parser, a parser must work with anything
> > > > > > from 1 byte per input to sizes being larger than a
> > > > > > single frame.
> > > > > >
> > > > > So a packet to a parser is basically a smaller unit to which the parser is fed
> > > > > data to? When I tried printing buffer size during parse, it shows 4096.
> > > >
> > > > > Does that mean the packet size was 4096?
> > > >
> > > > yes, that likely comes from
> > > > libavformat/img2dec.c:            size[0] = 4096;
> > > From my understanding of the documentation, the -packetsize option can
> > > change the
> > > value from 4096 to any particular I want right? However when I try setting the
> > > -packetsize option, the buf_size variable still shows up as 4096.
> >
> > img2dec hardcodes 4096, thats something you could change of course.
> > packetsize currently is listed with AV_OPT_FLAG_ENCODING_PARAM so its a muxer
> > option. Some demuxers seem to set packet_size though instead of using it as
> > input from the user
> > The header does not document packet_size with any detail
> >
> > Its probably best to add a new AVOption to img2dec to adjust the 4096
> 
> Can't the image2pipe demuxer option -frame_size be used instead?

yes, indeed, that should work

thanks

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have never wished to cater to the crowd; for what I know they do not
approve, and what they approve I do not know. -- Epicurus
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