Re: h.264 intra prediction

I am assuming that you are referring to motion compensation, and in this case I can answer your question.
For motion compensation, the receiver must know what block was used for the prediction in order to reconstruct the image. In JBIG, the predicting pixels are always the same, and so no side information needs to be transferred. However in h.264 (as in most modern codecs), the block which is used for prediction is identified by a motion vector. This vector must be sent to the decoder, and it takes up space in the output.
If you were to predict individual pixels, then a vector would need to be sent for each pixel. That makes for a very large amount of side information, so much so that it is not useful if your aim is compression! :)

The block sizes used form a good trade off between the space required to write the motion vectors, and the accuracy of the prediction.

Malcolm


boothmultipler@xxxxxxxxxxx wrote: 
 I wonder why h.264 uses block based prediction instead of pixelwise.
Wouldn't it be better if we predict the pixels using its neighbours
like JBIG does. Also it requires only one pass, in h.264 we need to try
several times to find the best prediction method. Also theres a little
overhead for each block.
 What is the reason to adapt such a method?

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