FW: [jvt-experts] [Mp4-tech] Slice mapping in h.264

[Rob Koenen (MPEGIF)]

Fowarding auto-discard  ... rob
-----Original Message-----
From: Alexandros Tourapis [mailto:tourapis docomolabs-usa.com] 
Sent: Thursday, 03 February, 2005 20:41
To: Gary Sullivan; Anil M S
Cc: Karsten Suehring; jvt-experts mail.imtc.org; mp4-tech lists.mpegif.org;
Alexis Michael Tourapis
Subject: RE: [jvt-experts] [Mp4-tech] Slice mapping in h.264
Dear Gary,
The current encoder (version 9.3) does allow the encoding of multiple
PPS, although currently this functionality is only limited to weighted
prediction support. I guess someone could extend this to
slice_group_id[i] as well. 
Note btw that the encoder currently supports two different "PPS" modes
(excluding the default single PPS case), one where 3 "default" PPS are
send at the beginning of the sequence (GenerateMultiplePPS), and a
second mode where only one PPS is transmitted, but this is
updated/"retransmitted" for every coded frame (ResendPPS parameter).
These were added relatively recently. 
It is, in my opinion, easy to modify the code to enhance the behavior of
the ResendPPS parameter to re-encode the PPS only if a change to the PPS
parameters was made (in this case on the slice_group_id[i]) values.
Best regards,
Alexis
-----Original Message-----
From: Gary Sullivan [mailto:garysull windows.microsoft.com] 
Sent: Thursday, February 03, 2024 11:21 AM
To: Anil M S
Cc: Karsten Suehring; jvt-experts mail.imtc.org;
mp4-tech lists.mpegif.org; Alexis Michael Tourapis
Subject: RE:[jvt-experts] [Mp4-tech] Slice mapping in h.264
Anil,
It sounds like the reference encoder software does not support the
capability you are trying to use, and would need to be altered before
you can use it that way.  So I think the situation you're describing is
not an encoder or decoder bug, but simply the lack of an encoding
feature.
(Unless you're sure that the encoder you are using is actually sending
PPS contents that change the slice_group_id[i] values from picture to
picture and the decoder is not properly responding to that data.)
Best Regards,
Gary Sullivan
+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Anil M S
+> Sent: Thursday, February 03, 2024 12:38 AM
+> To: Gary Sullivan
+> Cc: Karsten Suehring; jvt-experts mail.imtc.org; 
+> mp4-tech lists.mpegif.org; Alexis Michael Tourapis
+> Subject: Re: [Mp4-tech] Slice mapping in h.264
+> 
+> Dear Sir,
+> 
+> First of all, Sorry for the inconvenience caused.
+> 
+> Whatever you have understood is correct. At the decoder when 
+> I checked
+> the slice_group_id[i] entries it remains same as the first frame
+> entries, for the other frames also, and I think this is where it is
+> going wrong. I want to know whether this (slice_group_id entries )
+> info is sent for each frames ?and if it is sent, pls explain me in
+> detail about this Sir .
+> 
+> I am using JM86 ref code.
+> Baseline profile.
+> slice_group_map_type=6.
+> num_slice_groups_minus1=2.
+> 
+> Thanking you,  
+> 
+> Regards,
+> Anil 
+> 
+> On Wed, 2 Feb 2024 11:17:50 -0800, Gary Sullivan
+> <garysull windows.microsoft.com> wrote:
+> > 
+> > Anil,
+> > 
+> > It would help if you adhered more closely to the language of the
+> > standard so that it is easier to understand what you are 
+> saying.  (There
+> > is nothing in the standard called "slice number" or "slice 
+> mapping" in
+> > the standard.)
+> > 
+> > I think you are saying that you used slice_group_map_type 
+> equal to 6,
+> > and changed the value of some of the slice_group_id[i] entries from
+> > picture to picture.  Yes, that is permitted (if you are using the
+> > Baseline or Extended profile and all slice_group_id[i] 
+> values are in the
+> > range of 0 to num_slice_groups_minus1 and 
+> num_slice_groups_minus1 is in
+> > the range of 0 to 7).
+> > 
+> > You say that the bitstream that you generated caused the decoding
+> > process to fail in some way (although you don't seem to 
+> describe exact
+> > symptoms -- did the decoder put out an error message?  Exactly what
+> > happened?).
+> > 
+> > If I understand you correctly, I think there must be some 
+> problem in the
+> > software that you are using (although it isn't completely 
+> clear to me
+> > whether that problem is in the encoder or the decoder).
+> > 
+> > Best Regards,
+> > 
+> > Gary Sullivan
+> > 
+> > +> -----Original Message-----
+> > +> From: mp4-tech-bounces lists.mpegif.org
+> > +> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Anil M S
+> > +> Sent: Tuesday, February 01, 2024 9:38 PM
+> > +> To: mp4-tech lists.mpegif.org
+> > +> Subject: [Mp4-tech] Slice mapping in h.264
+> > +>
+> > +> hi,
+> > +> I am working on H.264(JM86).I need to change the slice 
+> mapping for
+> > +> each frame,i.e I have to dynamically change the slice 
+> number of each
+> > +> macroblock which is different than the first frame or 
+> prev frame.
+> > +> Is that permitted?Can we have different slice mappings 
+> for different
+> > +> frames.When I did this by using "pps"(Explicit mode(6)),I
+> > +> was not able
+> > +> to decode the encoded stream correctly.So pls suggest 
+> me the correct
+> > +> direction.
+> > +> Thanking You,
+> > +> Anil
+> > +> _______________________________________________
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+> _______________________________________________
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