Top field as reference for Bottom field

[zeeman_88]

Is there a way to predict bottom filed form the top filed in the h.264 standard? I mean can the top filed be used as reference the bottom field?

[neuron2]

You can achieve it by encoding with field pictures.

[Dark Shikari]

PAFF allows this. This is the one major advantage of PAFF over MBAFF.

[neuron2]

I mentioned "field pictures" rather than PAFF because the latter is not a syntax element of AVC (look for it in the spec!). It is an encoder strategy. The base syntax element is field pictures versus frame pictures.

[zeeman_88]

Thanks for the prompt answer...

Does x.264 does that?

So, in field mode, the reference list the bottom filed has the top field of the same picture listed?

[Dark Shikari]

Thanks for the prompt answer...

Does x.264 does that?

So, in field mode, the reference list the bottom filed has the top field of the same picture listed?x264 doesn't have a field mode; it uses MBAFF.

[neuron2]

Correct, it doesn't do field picture encoding.

[zeeman_88]

I tried this and it works well on P fields.

Now how should I make it work for B fields? I know, in h.264, B picture can be marked as reference for other Bs.

So the question is how to mark the top filed as reference B for the bottom filed B?

[neuron2]

You need hierarchical B pictures, i.e., your encoder must know how to use B pictures as references.

[zeeman_88]

Is that possible with Main profile? Or the encoder has to support higher profile? I don’t see anything in the slice header that can change the B to reference B.

Can anybody point me to where I should read in the standard for this? I searched the standard for reference B and couldn’t find what I want…

[Sergey A. Sablin]

Is that possible with Main profile? Or the encoder has to support higher profile? I don’t see anything in the slice header that can change the B to reference B.

Can anybody point me to where I should read in the standard for this? I searched the standard for reference B and couldn’t find what I want…

that's because there is no difference for P and B on how they're specified to be reference or not. it is same nal_ref_idc syntax element.

[zeeman_88]

Are you saying that to change B to B reference, all I need to change is the NAL priority!

How to add a reference B to the “reference list”? Don’t you need to that?

Also Sergey, this is an off topics qustion, do you work for Elecard?

[Dark Shikari]

Are you saying that to change B to B reference, all I need to change is the NAL priority!

How to add a reference B to the “reference list”?The frame gets implicitly added to the reference list in the case that its referenced. Any further reordering has to be done explicitly, of course.

[zeeman_88]

thanks Shikari.... And I assume, having b-ref is still vaild with Main profile.

[Dark Shikari]

thanks Shikari.... And I assume, having b-ref is still vaild with Main profile.Yes; I know of no profile limitations on references (in terms of reordering, MMCO, and various creative applications of the above).

[Sergey A. Sablin]

Are you saying that to change B to B reference, all I need to change is the NAL priority!
yes, exactly.

How to add a reference B to the “reference list”? Don’t you need to that?

if it's your encoder - make sure the frame you want to be reference will go to DPB. If it's not yours - check the code of the encoder you use. How it is done depends on specific implementation - this is just a piece of code.

Also Sergey, this is an off topics qustion, do you work for Elecard?
send your off topic questions through private messages.

[zeeman_88]

Thanks, Sergey, Shikari and neuron2 for the help...