question about pic_struct

[king_lijin]

Hello, everyone. I am confused about this parameter.

If pic_struct=4, can I say that this video is interlace?
In my opinion, we can not make this judgment only by pic_struct, but frame_mbs_only_flag和 field_pic_flag. Am right?

If so, what does pic_struct= 3 or 4 mean?

[akupenguin]

frame_mbs_only_flag=0 just means that there is some interlacing in the stream, not that every picture is interlaced. (It could even mean that the encoder just wasn't perfectly sure that there wasn't going to be any interlaced pictures.)
field_pic_flag signals interlacing in PAFF, but it's not used in MBAFF.

In addition to signalling interlacing, pic_struct can be used to signal telecine in streams that were compressed as progressive.

[king_lijin]

Thank you for your explanation.

In my project, there is no mixture of interlace and progressive case.
So my logic is:
If(frame_mbs_only_flag)
// progressive
Else
{
if(field_pic_flag)
//interlace
Else
// progressive
}

Do you know something about the pic_struct?

[kwtc]

- pic_struct indicates how the picture should be displayed.
- frame_mbs_only indicates how pictures are encoded.

Nothing prevents encoding progressive content using interlaced tools nor asking for interlaced display of progressive content (or the other way around).

If you wish to know whether the video is actually interlaced, you will need to analyse it using some algorithms.