[FFmpeg-devel] JPEG2000 decoder

rukhsana afroz rukhsana.afroz at gmail.com
Thu Jun 16 07:29:55 CEST 2011


Hi Michael,

On Wed, Jun 8, 2011 at 5:19 PM, rukhsana afroz <rukhsana.afroz at gmail.com>wrote:

> 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.
>
> I will be online this morning to fix the bug i mentioned to you. It will be
eaiser for me if we together go through this bug.

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


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