Confusion on motion estimation block diagram-MPEG video compression-:

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Discussion Overview

The discussion revolves around the motion estimation block diagram in MPEG video compression, focusing on specific aspects of block matching, frame segmentation, and prediction error coding. Participants express confusion regarding the details and terminology used in the documentation related to these concepts.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions why frame n is not segmented into blocks, suggesting that it is not clear from the document.
  • Another participant asserts that frame n is indeed segmented into blocks, referencing the figure that implies block operations.
  • Concerns are raised about the lack of inputs from frame (n-1) for block matching, with one participant stating that such inputs are present in the figure.
  • Participants discuss the role of prediction error coding, noting that it involves sending a correction factor to account for motion between frames.
  • There is a request for clarification on the flowchart and the block matching process, indicating ongoing confusion about the described operations.
  • A suggestion is made to consult multiple sources for better understanding when a document is confusing.

Areas of Agreement / Disagreement

Participants express differing views on the clarity of the documentation and the presence of certain operations. While some assert that the document does include necessary information, others remain confused and seek further clarification. The discussion does not reach a consensus on the clarity of the material.

Contextual Notes

Participants highlight potential ambiguities in the document's wording and figures, which may contribute to misunderstandings regarding the block matching algorithm and prediction error coding. Specific page references are made, but the effectiveness of these references remains contested.

shivajikobardan
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Homework Statement
block matching algorithm confusion
Relevant Equations
none
svGOSnpFO94tutB2h-927rxVYRDUGzi-JF9FYs9hKivGdCvrAP.png

My doubts are as follows-:

-> Why frame n is not segmented to blocks?

-> Why no inputs from (n-1) side for block matching?
-> What do we do in prediction error coding?

Source-: https://homepages.inf.ed.ac.uk/rbf/CVonline/LOCAL_COPIES/AV0506/s0561282.pdf

I have read this many times but that didn’t help to clear my doubts.



This video. This confused the hell out of me.
 
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shivajikobardan said:
Homework Statement:: block matching algorithm confusion
Relevant Equations:: none

-> Why frame n is not segmented to blocks?
It is.
The poorly worded description you have only implies the block operation, for instance by showing it in the figure as "Block Matching." Later text also describes operations that can only be done on blocks.

-> Why no inputs from (n-1) side for block matching?
There is.
Again the figure shows Block Matching output for the two frames feeding the "Prediction Error Coding" operation.

Both of the above are explained (sort of) on pgs 3 and 4 of the document you linked.

-> What do we do in prediction error coding?
The Block Matching searches the blocks in the n-1 frame, and if it finds a close match to the current block in the n frame, it sends an instruction to the receiver to use that already received block from n-1.
However that n-1 block is not always an exact match due to image motion between frames.
The Prediction Error Coding then sends a 'Correction' factor that the receiver applies to n-1 frame to account for any motion that may have occurred between frames.

Note that this requires the receiver to keep a copy of the reference (previous) frame for comparison.

Hope this helps!

Cheers,
Tom

p.s. By the way, I found the video useless, I could not understand the accent of the presenter.
 
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Tom.G said:
It is.
The poorly worded description you have only implies the block operation, for instance by showing it in the figure as "Block Matching." Later text also describes operations that can only be done on blocks.There is.
Again the figure shows Block Matching output for the two frames feeding the "Prediction Error Coding" operation.

Both of the above are explained (sort of) on pgs 3 and 4 of the document you linked.The Block Matching searches the blocks in the n-1 frame, and if it finds a close match to the current block in the n frame, it sends an instruction to the receiver to use that already received block from n-1.
However that n-1 block is not always an exact match due to image motion between frames.
The Prediction Error Coding then sends a 'Correction' factor that the receiver applies to n-1 frame to account for any motion that may have occurred between frames.

Note that this requires the receiver to keep a copy of the reference (previous) frame for comparison.

Hope this helps!

Cheers,
Tom

p.s. By the way, I found the video useless, I could not understand the accent of the presenter.
Hmm you're telling it includes everything..but it isn't included in figure I'm confused..🧐..can you explain 1 round of this flowchart in small brief? I'm really confused..btw what happens in block matching?
 
Very general hint: whenever I find a document on some technology confusing I google other sources to do a cross check. The more, the better.
 
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