[FFmpeg-devel] [PATCH] fate/jpeg2000dec: add selected conformance codestreams from ISO/IEC 15444-4

[WATANABE Osamu]

Yes, it is related to the potential problem.

The problem may be here:
https://github.com/FFmpeg/FFmpeg/blob/40dda881d6ad761b4589c3078b925e0d849546b3/libavcodec/jpeg2000dec.c#L2139

Shifting down by 16 bits here is too much because it will cancel the value of "1" (=0.5) below the binary point.


> On Aug 23, 2024, at 1:36, Pierre-Anthony Lemieux <pal at sandflow.com> wrote:
> 
> On Thu, Aug 22, 2024 at 2:24?AM WATANABE Osamu
> <owatanab at es.takushoku-u.ac.jp> wrote:
>> 
>> Hi Pierre, Tomas,
>> 
>> For lossy codestreams, I found a potential problem on the current 9x7 integer IDWT (which will be activated with the +bitexact flag.)
> 
> Probably related?
> 
> https://trac.ffmpeg.org/ticket/10123
> 
>> 
>> I have confirmed that FFMPEG passes all the test cases without the flag.
>> 
>> The problem has been locally solved with the updated code, however, the patch set is not yet ready.
>> (It won't take long)
>> 
>> Best,
>> Osamu
>> 
>> 
>>> 2024/08/22 1:01、Pierre-Anthony Lemieux <pal at sandflow.com>のメール:
>>> 
>>> ?On Wed, Aug 21, 2024 at 8:54?AM Tomas Hardin <git at haerdin.se> wrote:
>>>> 
>>>> man 2024-08-19 klockan 23:03 -0700 skrev pal at sandflow.com:
>>>>> From: Pierre-Anthony Lemieux <pal at palemieux.com>
>>>>> 
>>>>> ---
>>>>> tests/fate/jpeg2000.mak                  | 129
>>>> 
>>>> I presume you've tested that the frames match the references as
>>>> required. If so then it looks OK to me
>>> 
>>> @osamu you checked that all the codestreams decoded within acceptable
>>> limits, right? If so, I will add you as co-author.
>>> 
>>> (I have only checked a few of them for accuracy per the spec. I have
>>> checked all of them for memory leaks/crashes.)
>>> 
>>>> 
>>>> /Tomas
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