[FFmpeg-devel] JPEG2000 decoder

[rukhsana afroz]

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. Context will only be
initialized at the beginning of cblk decode. Whereas, data will be
initialized for each segment iterated inside the code block. Also,
decode_sigpass, refpass, clnpass uses the variable "bpno" in order to
calculate mask, phalf, nhalf. These variables are important. I think, there
need some modifications on these too. Please let me know how you do think.

Thanks

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