[M4IF Technotes] Re: Need advice on Motion Estimation, please advise....

[cloverleafland mail.hongkong.com]

Dear Mithun Nayak, 
Thanks for that... but I am still confused about the need of motion vector of chroma blocks... If we only need to perform motion estimation on Y blocks, then why do we still need to store the motion vectors for U & V blocks?
Regards,
Clover
> Hi ...
> 
> Motion estimation need not necessarily be done on
> 16 * 16 blocks.
> Infact if the search is performed on 4blocks of
> 8*8 then it is called 4MV searching.
> But that would consume a lot of time..searching
> for 4 blocks independently.
> 
> Also ...motion estimation isnt carried out for
> chroma blocks..but the decoder assumes that
> the value of motion vector shall be
> 1) half that of luma vector (if search is for
> 16*16 block)
> 2) sum of non transparent luma vectors % num of
> non transparent luma blocks in a mcroblock (for 4
> MV)
> 
> The  chrominance Motion vectors have to be rounded
> appropriately as suggested in ISO 14496-2..
> 
> regards
> Mithun Nayak
> 
> 
> -----Original Message-----
> From: technotes-admin   lists.m4if.org
> [mailto:technotes-admin   lists.m4if.org]On Behalf
> Of
> cloverleafland   mail.hongkong.com
> Sent: Monday, October 28, 2023 4:02 PM
> To: technotes   lists.m4if.org
> Subject: [M4IF Technotes] Re: Need advice on
> Motion Estimation, please
> advise....
> 
> 
> Dear all,
> 
> I am currently working on a project to build a
> MPEG-4 encoder. I got confusion on the process of
> motion estimation. would anyone help explaining
> why the motion estimation is done on 16x16 block
> based but not in 8x8 block based?
> 
> Also, for a macroblock, it consists of 4 8x8 Y
> blocks and 1 8x8 U block and 1 8x8 V block, would
> anyone advise whetehr the motion estimation on Y,
> U and V are done seperately or not?
> 
> Thanks so much....
> 
> Regards,
> Clover
> 
> 
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