[FFmpeg-devel] JPEG2000 decoder

[rukhsana afroz]

Hi Michael,

On Fri, May 27, 2011 at 7:10 AM, Michael Niedermayer <michaelni at gmx.at>wrote:

> On Fri, May 27, 2011 at 04:28:29AM -0700, rukhsana afroz wrote:
> > Hi Michael,
> >
> > On Tue, May 24, 2011 at 1:10 AM, rukhsana afroz <
> rukhsana.afroz at gmail.com>wrote:
> >
> > > Hi Michael,
> > >
> > > On Fri, May 20, 2011 at 10:49 PM, rukhsana afroz <
> rukhsana.afroz at gmail.com
> > > > wrote:
> > >
> > >> Hi Michael,
> > >>
> > >>
> > >> On Thu, May 19, 2011 at 3:38 PM, rukhsana afroz <
> rukhsana.afroz at gmail.com
> > >> > wrote:
> > >>
> > >>>
> > >>>
> > >>> On Thu, May 19, 2011 at 3:32 PM, rukhsana afroz <
> > >>> rukhsana.afroz at gmail.com> wrote:
> > >>>
> > >>>> Hi Michael,
> > >>>>
> > >>>>
> > >>>> On Sun, May 15, 2011 at 5:00 PM, Michael Niedermayer <
> michaelni at gmx.at>wrote:
> > >>>>
> > >>>>>
> > >>>>> We will have to implement multiple codeword segments.
> > >>>>>
> > >>>>> Also sofar, good work!
> > >>>>>
> > >>>>>
> > >>>> Sorry for the late reply. If I implement codeblock segment, its
> going to
> > >>>> affect from packet decoding process to the subsequent deoding
> process till
> > >>>> the last. Therefore, I have to be properly planned in order to
> accomplish
> > >>>> these changes. Here, I have put patch for incorporating multiple
> codeblock
> > >>>> segment. I had to create two more structures and modify J2KCblk
> sturucture
> > >>>> as well. This patch is just for the modification/creation on the
> structures.
> > >>>> I am also writing some miscellaneous function and I will post those
> in my
> > >>>> subsequent emails.
> > >>>>
> > >>>
> > >> I have modified the decode_packet function incorporating multiple
> codeword
> > >> segment. Here, I have attached the patch for the required changes. I
> have
> > >> taken the help from jasper code while writing this code, because only
> the
> > >> document is not sufficient to incorporate these changes. I have not
> tested
> > >> this code yet. Once, I test it, I also let you know. If you have any
> > >> suggestion on this patch, please let me know.
> > >>
> > >>
> > >>
> > >
> > > While doing arithmetic coding operation in decode_cblk function one
> > > term/variable is "bpno". Coding operation (decode_sigpass,
> decode_refpass,
> > > decode_clpass) uses this variable to determine the data of each
> codeblock in
> > > different contexts. This variable has been set in our decoder:
> > >
> > >
> > > bpno = cblk->nonzerobits - 1
> > >
> > > And, jasper has set this variable as follows:
> > >
> > > bpno = band->roishift + band->numbps - 1 - (cblk->numimsbs +
> (seg->passno +
> > > i - cblk->firstpassno + 2) / 3);
> > >
> > > band->roishift is the value got from processing the RGN marker and
> > > band->numbps is also the value got from some other marker. Our decoder
> has
> > > not processed this marker.  cblk->numimsbs is similar to our decoder's
> > > cblk->nonzerobits. Other part of this variable is segment specific and
> that
> > > makes sense. I need you suggestion on how to set this variable. I will
> > > explain more tomorrow on IRC chat.
> > >
> > >
> > >
> > Here, I have attached two patches which cove all changes due to multiple
> > codeblock segment. I have tested decode_packet function, but not
> decode_cblk
> > yet.
>
> thx, some comments below
>
> [...]
> > -/* Tier-1 coding pass types. */
> > -#define      J2K_SIGPASS     0       /* significance */
> > -#define      J2K_REFPASS     1       /* refinement */
> > -#define      J2K_CLNPASS     2       /* cleanup */
>
> that contains tabs, tabs cannot be commited to our git
> i suggest you configure your editor not to insert tabs or trailing
> whitespace (many editors can be configured that way)
>
> also the patch is reversed (like diff a b instead of diff b a )
>
> the second patch doesnt apply:
>  patching file libavcodec/j2kdec.c
> Hunk #1 succeeded at 463 (offset -5 lines).
> Hunk #2 succeeded at 570 (offset -21 lines).
> Hunk #3 FAILED at 604.
> Hunk #4 succeeded at 608 (offset -27 lines).
> Hunk #5 succeeded at 758 (offset -27 lines).
> Hunk #6 succeeded at 764 (offset -35 lines).
>
> [...]
>
>
> if you use git you can turn commits into patches trivially with
> git format-patch -2
> (that would turn the last 2 commits into patches together with author&
>  commit message)
>
> Sorry for the late reply. Problem is, right now i am debugging the code and
thats why there are lots of log messages in the code, therefore the previous
patches' lots of hunk failed in the code you have. I have my latest code in:

https://github.com/rukhsana/j2k/tree/r10

You can check it out from here. Once, we are sure that the code is perfect,
I will make the patch on the original code, then you can commit to ffmpeg.
Right now I have found a problem in the decode_packet function. At the
beginning of decode_packet function, there are following lines:

if (!(ret = get_bits(s, 1))){
        //j2k_flush(s);
        return 0;
    } else if (ret < 0)
        return ret;

This bit checks whether the packet header exists or not. I have given log
messages before and after of these lines. I get the pointer (s->buf) does
not move after these lines. This problems even exist for the other files
which can be correctly decoded, For the file p1_01.j2k, I get the following
log messages before and after of these lines.

before flush pointer: 152
after flush pointer: 152

But from the jasper code, if you check, pointer moves to 153. Therefore,
some of the packet header information apparently look correct, but actually
it stucks to a problem if i consecutively decode the following packets. I am
checking the get_bits function. Could you please have a look at this
function?

Thanks


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