[Mp4-tech] [video]AVC field selection

[Andrew Palfreyman (cisco)]

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