[Mp4-tech] [H.264] Initialisation process for ref. pic. list infields

[Gary Sullivan]

Marco et al,
You need to pay attention to the exact stage of the processing at which
the quoted statement applies.  The current picture has not yet been
decoded.  The quoted statement is simply saying that when you are
decoding the second field of a frame you can use the first field as a
reference picture.
In this case the second field is the current picture.  We don't use the
current picture as a reference for decoding itself.
If you look close enough at the reference software, I am confident that
you will not find a difference between what it is doing and what the
spec is saying in this regard.
Best Regards,
-Gary Sullivan
+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of 
+> Marco.Miehe sci-worx.com
+> Sent: Thursday, August 18, 2023 8:34 AM
+> To: Mp4-tech lists.mpegif.org
+> Subject: [Mp4-tech] [H.264] Initialisation process for ref. 
+> pic. list infields 
+> 
+> Dear Members
+> 
+> I have a question regarding the Initialisation process for reference
+> picture list for P slices in fields.
+> 
+> In the standard ITU-T Rec. H.264 chapter 8.2.4.2.2 
+> I found the following sentence.
+> "When the current field is the second field (in decoding order) of a
+> complementary reference field pair 
+> and the first field is marked as "used for short-term reference", the
+> first field is included in the 
+> list of short-term reference frames refFrameList0ShortTerm."
+> 
+> What does it mean exactly?
+> Only the first field of a complementary reference field pair 
+> (the first
+> field is marked as "used for short-term reference")
+> is included in the refFrameList0ShortTerm and we ignore the second
+> field?
+> 
+> I mean in the Reference Software JM 9.7 they don't check 
+> this. If this
+> Frames or Field is "used for reference" they include
+> this frame or field in the refFrameList0ShortTerm and do 
+> nothing more.
+> 
+> I'd appreciate if some one clarifies this.
+> 
+> 
+> Best regards,
+> 
+> Marco Miehe
+> 
+> 
+>   
+> 
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