Quote:
Originally Posted by n0an
The higher the bar means all details below that threshold will not be encoded - that means they will remain as it is?
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No, it doesn't. Each coefficient in the DCT transformed macroblock will be divided through the corresponding entry in the quantization matrix. It's important to understand the
DCT transform, before you try to understand what quantization matrices do! After division, the DCT coefficients are rounded - that's what causes loss! The higher the value in the quantization matrix, the higher the rounding error (loss) for the corresponding DCT coefficient. That's why we use
high quantization values for the "high" frequencies: The coefficients for the "high" frequencies usually have low values anyway. If we divide that through a high value (from the quant matrix), it will be extremely small and thus rounded to
zero, most likely. So after
quantization we have a lot of zero coefficients in our transformed DCT block. This doesn't save us any bits yet, but it
does in the next step, which is
entropy coding! At the same time the loss in the "higher" frequencies ("fine detail") isn't as noticeable as loss in the "lower" frequencies ("coarse" detail).
Furthermore it is important to understand that all this high/low frequency to fine/coarse detail mapping only applies to I-Frames. In P- and B-Frames the story is a bit different:
http://forum.doom9.org/showpost.php?...9&postcount=17
Quote:
Originally Posted by n0an
P.S. I am mainly looking for XviD and HD (x264) based matrix.
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As said before: Most likely you won't ever need any custom matrices for x264. It works best with the default (flat) matrix. That's because most things people tried to achieve with custom matrices in the past is done by x264's Psy-optimizations nowadays, only in a better way. So again: Don't mess with custom matrices, unless you know exactly why you need them...
Quote:
Originally Posted by n0an
Anyway, I am wanting to have a low and medium bitrate based matrix. I am trying to understand each matrix in the CQM editor.
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Look here for examples:
http://forum.doom9.org/showthread.php?s=&threadid=83125