[Mp4-tech] Question regarding slice groups

[Wesley De Neve]

Dear Nitin,
The main incentive behind the introduction of slice groups is to enable a coding tool called Flexible Macroblock Ordering (FMO). There are already quite some publications available that deal with this subject. The following manuscript might be of particular interest to you:
Peter Lambert et al., Flexible macroblock ordering in H.264/AVC. Journal of Visual Communication & Image Representation. Elsevier. Vol. 17. 2006. pp. 358 - 375
Regarding your last question: motion vectors can point to macroblocks that belong to other slice groups. However, an encoder may use the motion-constrained slice group set SEI (Supplemental Enhancement Information) message to signal to the decoder that it has restricted motion vectors in this way. This might be useful for content adaptation purposes (ROI extraction), etc.
Best regards,
-Wesley 
  ----- Original Message ----- 
  From: Nitin PAI 
  To: mp4-tech lists.mpegif.org 
  Sent: Thursday, May 25, 2024 6:43 AM
  Subject: [Mp4-tech] Question regarding slice groups
  Hi, 
  I want to know the significance of introducing slice groups.  I understand that the slices are needed for error resilience.  Does slice groups serve only the need of grouping the slices in raster order or ease of specifiying the slice group map?  Or is there any other things like a slice group is an independent decodable entity ( i mean the motion vectors should be constrained to lie inside the slice group only?) 
  Thanks,
  Nitin  
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