Quantization Logic - How does the encoder work?

[redfordxx]

Hi,

for the reason again continuing work on my video smoother, I have a question, maybe some one knows the answer. Hope this is good forum for this topic


How much can strength of quantisation differ within one frame?

Imagine having one frame of encoded video. There are places with high detail and places with low detail. Places with higher quantisation and lower quantisation (I think).
Let's say, there is one block with really high detail in the middle of the frame, it means with low quantisation.
Somewhere else, there is low detail or even one color block. Now, the question is why. Is that because there was no detail before encoding, or because it was highly quantized? Does the existence of the low quantized block in the middle say, that everywhere else is low quantisation also, coz the quantizer does not differ much within a frame?

Let's be interested in keyframes only...for now.

Thanks for explanation
R.