[Mp4-tech] [video]AVC field selection

[Gary Sullivan]

I see - that's right.  Unlike in MPEG-2, the frame/field structuring of the prediction and the residual transform difference are coupled together in AVC.
Best Regards,
Gary Sullivan
+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of 
+> Andrew Palfreyman (cisco)
+> Sent: Wednesday, June 20, 2023 9:40 PM
+> To: dthoang yahoo.com; mp4-tech lists.mpegif.org
+> Subject: Re: [Mp4-tech] [video]AVC field selection
+> 
+> Indeed -  in the case I'm considering, the current MB type 
+> is frame and it 
+> is the case that num_ref_idx_l0_active_minus1 = 0.
+> That being so, we appear to be agreeing that it is not 
+> possible to reference 
+> just a single field parity from such an MB.
+> And what I want to do is just that, unfortunately.
+> 
+> Best,
+> Andrew
+> 
+> ----- Original Message ----- 
+> From: "Dzung Hoang" <dthoang yahoo.com>
+> To: "'Andrew Palfreyman (cisco)'" <anpalfre cisco.com>; 
+> <mp4-tech lists.mpegif.org>
+> Sent: Wednesday, June 20, 2023 9:21 PM
+> Subject: RE: [Mp4-tech] [video]AVC field selection
+> 
+> 
+> > According to 7.3.5.1, the inference of ref_idx_l0 only 
+> occurs for frame 
+> > MBs
+> > when num_ref_idx_l0_active_minus1 = 0. Is there another 
+> case that I'm
+> > missing? If not, then no field-based prediction can happen 
+> in the case you
+> > are concerned with.
+> >
+> > Regards,
+> > - Dzung Hoang
+> >
+> > -----Original Message-----
+> > From: Andrew Palfreyman (cisco) [mailto:anpalfre cisco.com]
+> > Sent: Wednesday, June 20, 2023 10:46 PM
+> > To: dthoang yahoo.com; mp4-tech lists.mpegif.org
+> > Subject: Re: [Mp4-tech] [video]AVC field selection
+> >
+> > The problem I have with that approach is that in 7.4.5.1 it states
+> > "When only one reference picture is used for inter 
+> prediction, the values 
+> > of
+> >
+> > ref_idx_l0[mbPartIdx] shall be inferred to be equal to 0".
+> > So even though the ref. pic has two field parities, these cannot be
+> > differentiated via a zero value of ref_idx.
+> >
+> > Best,
+> > Andrew
+> >
+> > ----- Original Message ----- 
+> > From: "Dzung Hoang" <dthoang yahoo.com>
+> > To: "'Andrew Palfreyman (cisco)'" <anpalfre cisco.com>;
+> > <mp4-tech lists.mpegif.org>
+> > Sent: Wednesday, June 20, 2023 8:08 PM
+> > Subject: RE: [Mp4-tech] [video]AVC field selection
+> >
+> >
+> >> Try LSB of ref_idx XOR with current field parity.
+> >>
+> >> Regards,
+> >> - Dzung Hoang
+> >>
+> >> -----Original Message-----
+> >> From: mp4-tech-bounces lists.mpegif.org
+> >> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of 
+> Andrew Palfreyman
+> >> (cisco)
+> >> Sent: Wednesday, June 20, 2023 12:04 PM
+> >> To: mp4-tech lists.mpegif.org
+> >> Subject: [Mp4-tech] [video]AVC field selection
+> >>
+> >> For AVC, I am trying to identify (with little success so far) the 
+> >> semantic
+> >> equivalent of what in MPEG2 was called 
+> motion_vector_field_select. How is
+> >> this accomplished in AVC?
+> >>
+> >> Best,
+> >> Andrew
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