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

[Carl Eugen Hoyos]

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?

Carl Eugen