[M4IF Technotes] Video Object Plane Header

[Gary Sullivan]

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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