[M4IF Technotes] Video Object Plane Header

[Luca Piccarreta]

I suppose that vop_coded is in that position on purpose, to remember
you that for IVOP and PVOP you must calculate the Future and
Past Reference times, and swap the Future and Past VOP.
At least, I hope.
:)
Luca Piccarreta.
----- Original Message -----
From: "Gary Sullivan" <garysull   microsoft.com>
To: "Nitin Gupta--DSP, Noida" <gnitin   noida.hcltech.com>;
<technotes   lists.m4if.org>
Sent: Tuesday, April 23, 2024 2:45 PM
Subject: RE: [M4IF Technotes] Video Object Plane Header
>
> 1) Regarding why the order was chosen for vop_coded
> versus vop coding type -- I don't know.  Just a quirk
> I suppose.  Doesn't seem significantly harmful, but perhaps
> it's not ideal design.
>
> 2) Regarding quant, yes I believe it must be in the range of
> 1 - 31, at least unless the 10-bit or 12-bit options are in use.
> Since quant=0 has no defined meaning, I don't see any value
> in being able to send it.  (quant=0 could also potentially
> cause start code emulation, depending on what syntax elements
> occur in the same neighborhood.)
>
> Best Regards,
>
> Gary
>
> +> -----Original Message-----
> +> From: Nitin Gupta--DSP, Noida [mailto:gnitin   noida.hcltech.com]
> +> Sent: Monday, April 22, 2024 4:12 AM
> +> To: technotes   lists.m4if.org
> +> Subject: [M4IF Technotes] Video Object Plane Header
> +>
> +>
> +> Hi all,
> +> I have some doubts regarding the header of the
> +> video object plane in an Mpeg4 stream. I hope that somebody
> +> would help me out .
> +>
> +> 1) In the video object plane header the first parameter
> +> that is encoded is the vop coding type & the parameter
> +> vop_coded ( that tells whether the vop is coded or not )
> +> comes later. I want to know why are these parameters
> +> encoded in this order since if vop is not coded then we are
> +> hardly bothered that the vop coding type is I or P.
> +> Shouldn't the vop_coded parameter come before the
> +> vop coding type so that if vop is not coded we need not
> +> decode any further information ?
> +>
> +> 2) Another parameter that comes in the vop header is
> +> vop_quant. As i can interpret its value can range from
> +> 1 to 31. But i would like to know that is the value 0 for
> +> vop_quant illegal ? Because i think we can have the
> +> value of vop_quant in the header to be 0 & then we can
> +> have the value of d_quant to be +1 or +2 in the first macroblock
> +> of the vop ( provided that the mb_type of the macroblock
> +> is either 1 or 4 ) & that would put the things right.
> +>
> +>
> +> Thanx & Regards,
> +> -----------------------------------------------------------------
> +> Nitin Gupta
> +> Member Technical Staff,
> +> MicroProcessor Software Group (MPSG),
> +> A-5, Sector 24,
> +> HCL Technologies, Noida 201301, India
> +> +91 11 91 4534265-66 (O) Extn: 2561
> +> gnitin   noida.hcltech.com
> +> g_nitin007   yahoo.com
> +>
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