[FFmpeg-devel] JPEG2000 decoder

[rukhsana afroz]

Hi Michael,

On Wed, Jun 15, 2011 at 10:29 PM, rukhsana afroz
<rukhsana.afroz at gmail.com>wrote:

> 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.


Here, I have attached the patch for debugging jasper's mqc.

Thanks


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