[Mp4-tech] H.264 doubts

[Alexis Michael Tourapis]

Dear Pavan,
img->block_x and img->block_y correspond to 4x4 block indices, not 8x8. I
guess (could be wrong) your confusion comes from the fact that the number of
MBs in a row or in a column is multiplied by 4 to result in the number of
blocks. This is obvious since you should be checking each dimension
separately and not as a block (i.e. one line of pixels with width img_width
is subdivided into img_width/16 macroblock pixels, or img_width/4 4x4 block
pixels. However an image of size img_width * img_height, is divided into
(img_width/16)* (img_height/16) mbs, or (img_width/4)* (img_height/4) 4x4
blocks). 
Best regards,
Alexis
  _____  
From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of pavan kumar nittala
Sent: Thursday, February 24, 2024 9:10 PM
To: pasunuti prabhakar
Cc: mp4-tech lists.mpegif.org
Subject: Re: [Mp4-tech] H.264 doubts
Prabhakar
Assume QCIF in which 
Width and Height in terms of pixels, Macroblocks and 8x8 blocks 
are as follows
WIdth = 176 (pixels)  width = 11 (MBs) width = 44(8x8 Blocks)
Height = 144 (pixels)
  = 9 (MBs) Height = 36 (8x8 Blocks)
img->block_x  Represents the Block number starting from the 1st macroblock
...
On Thu, 24 Feb 2024 pasunuti prabhakar wrote :
>Hello Experts,
>
>      I am working on the JVT9.2 decoder. I have certain doubts in code..
>
>    What exactly the variables
"block_x","block_y","pix_x","pix_y","pix_c_x","pix_c_y" represents. With
respect to a frame, what exactly these variables  indicates.
>
>Thanks in advance.
>
>Regards
>Prabhakar
>
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