[Mp4-tech] JM reference software problem

[Tourapis, Alexis]

Dear Tomislav,
With regards to the IDR PSNR that could just be due to a known limitation in the software. The PSNR computation in the JM needs to be moved at a different location (i.e. when a picture is removed from the DPB) to make sure that pictures are compared in appropriate order but we have not found the time to do so. I would therefore always suggest to consider using an external tool to verify performance.
With regards to not using all P as references, note that in that case frame_num increments do depend on whether a coded frame is a reference or not. That is frame_num is expected to increase after you have encoded a reference picture, but it should not if you have encoded a non reference picture. If for example you have Pictures I0p1P2p3p4P5P6, with lowercase "p" being non reference pictures, Your frame_num should look like this : 0, 1, 1, 2, 2, 2, 3. As you can see in this scenario, frame_num increased on the first non-reference after a reference picture, while also it increased also for P6 (a reference) which follows another reference picture. 
I cannot comment on the color issues you are having. Maybe your intra prediction is not initialized properly or you might be having some rounding issues. I would suggest also checking with the JM since that provides already a working implementation of the process.
Best regards,
Alexis
-----Original Message-----
From: mp4-tech-bounces lists.mpegif.org [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Tomislav Muic
Sent: Monday, September 24, 2023 6:13 AM
To: Alexis Michael Tourapis
Cc: mp4-tech lists.mpegif.org
Subject: Re: [Mp4-tech] JM reference software problem
hello,
thanks for answer, it was a part of problem, but I still have some problems
when I change that every P slice ihas nal_reference_idc=1
http://www.best.hr/share/tmuic/test.264
 it decodes in JM, although it seems that SNR drops unusually in second IDR frame
but I want to use not every P frame as reference, but only if it is different more than certain threshold, otherwise I want to use I-frame, and this does not pass JM
http://www.best.hr/share/tmuic/test1.264
another question, I get some color/luminance drift between different IDR pictures, does anybody know what could be propable cause, I use transformation and quantization as defined in paper at www.vcodex.com http://www.best.hr/share/tmuic/test2.avi
On 9/24/07, Alexis Michael Tourapis <alexismt charter.net> wrote:
> Dear Tomislav,
>
> It seems that all your P slices belong to a picture with nal_reference_idc set to 0 (i.e. they are not set as references). Can you double check your encoder?
>
> Alexis
>
> ---- Tomislav Muic <tomislav.muic gmail.com> wrote:
> > I am having problem with decoding my stream with JM software
> >
> > I get error Unintentional loss of pictures occurs.
> >
> > Stream is decoded in video player just fine
> >
> > I send SPS and PPS first and then
> >
> > AU delimiter
> > IDR pic - I slice
> >
> > AU delimiter
> > P slice
> > ....
> > AU delimiter
> > Pslice
> > end of sequence
> >
> > For frame_num I reset it to zero and add 1 for every next pic, for 
> > pic_order_cnt_lsb I send same value as frame_num
> >
> > I can't find why reference software can't read stream, and it is 
> > decoded normally in video player.
> >
> >
> >
> > Here is short sample of avi stream and NAL stream
> > http://www.best.hr/share/tmuic/test.264
> > http://www.best.hr/share/tmuic/ftest.avi
> >
> > --
> > Tomislav Muić
> >
> > _______________________________________________
> > NOTE: Please use clear subject lines for your posts. Include [audio, [video], [systems], [general] or another apppropriate identifier to indicate the type of question you have.
> >
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> > php
>

--
Tomislav Muić
_______________________________________________
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