[FFmpeg-devel] JPEG2000 decoder

rukhsana afroz rukhsana.afroz at gmail.com
Thu Jun 9 02:19:26 CEST 2011


Hi Michael,

On Sat, Jun 4, 2011 at 5:23 PM, Michael Niedermayer <michaelni at gmx.at>wrote:

> On Sat, Jun 04, 2011 at 06:06:51AM -0700, rukhsana afroz wrote:
> > Hi Michael,
> >
> > On Sat, Jun 4, 2011 at 5:26 AM, rukhsana afroz <rukhsana.afroz at gmail.com
> >wrote:
> >
> > > Hi Michael,
> > >
> > >
> > > On Fri, Jun 3, 2011 at 10:36 AM, Michael Niedermayer <michaelni at gmx.at
> >wrote:
> > >
> > >> On Fri, Jun 03, 2011 at 02:25:26AM -0700, rukhsana afroz wrote:
> > >> > Hi Michael,
> > >> >
> > >> > On Wed, Jun 1, 2011 at 3:42 AM, rukhsana afroz <
> > >> rukhsana.afroz at gmail.com>wrote:
> > >> >
> > >> > > Hi Michael,
> > >> > >
> > >> > >> maybe jaspers and ours advance the pointer at a slightly
> different
> > >> > >> spot in the implementation
> > >> > >>
> > >> > >>
> > >> > > As per the discussion on IRC chat, I checked where s->bit_index
> gets
> > >> > > modified. I see, in our decoder that s->bit_index has been
> manually
> > >> set to 8
> > >> > > at the beginning of decoding packet. whereas, in jasper, I did not
> see
> > >> this.
> > >> > > Also, jasper always reads the entire byte to check present bit
> even
> > >> for
> > >> > > other files, like file1.jp2 etc. Whereas, our decoder does not do
> so.
> > >> I need
> > >> > > your suggestion on this as i do not find any clue in the doc for
> this.
> > >> I am
> > >> > > waiting for you on the IRC chat.
> > >> > >
> > >> > >
> > >> > >
> > >> > >
> > >> > >
> > >> > I have rebased the codebase against ffmpeg and also decode_packet
> > >> function
> > >> > works properly comparing with jasper. However, it gets segmentation
> > >> fault
> > >> > somewhere in decode_cblk function for adding new code. Tomorrow I
> will
> > >> be in
> > >> > chat to discuss this code. My new code rebased with ffmpeg is in:
> > >> >
> > >> > https://github.com/rukhsana/ffmpeg_j2k
> > >>
> > >> thanks
> > >>
> > >> btw
> > >>
> > >> floor_log2() can be replaced by av_log2()
> > >>
> > >>
> > > I have pushed another branch r2 now. Could you please help check
> whether
> > > the initialization of contexts (which has been done for every codeblock
> > > segment) is ok compared with jasper? I think, there some problem in
> this. I
> > > am checking as well. There are some problems in decode_cblk function, i
> need
> > > to debug thoroughly.
> >
> >
> >
> > ff_mqc_initdec function have both context and data initialization. I
> think,
> > context and data initialization should be separated.
>
> yes
>
> I have fixed some of the problems of decode_cblk function, right now it
does not get segmentation fault. However, code is not working. We still need
to fix a lot of stuffs. My new code is in the branch r3.  I have one concern
regarding decode_tile function. Actually, decode_cblk is called from
decode_tile function. I found, the sequence of generated code blocks inside
the decode_packet function does not follow sequence in decode_tile function.
Therefore, I am having trouble with debugging, I think we need to first fix
the generation sequence of code block both in decode_packet and decode_tile
function, so that it becomes easy to follow. I found, jasper follows the
sequence.

Thanks

-- 
Rukhsana Ruby
Phd Student
Department of Electrical & Computer Engineering
The University of British Columbia
============================


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