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Subband stepsize is always less than one in OpenJPEG. This means that quantization is not taking place: i.e. DWT coefficients are being mapped to a larger dynamic range, rather than a smaller one,
since quantization take place by multiplying coefficients by the reciprocal of the step size.
This is very inefficient. I don't think this is a conformance issue, because encoders are free to choose the quantization step. But, I would guess this situation creates a serious hit in performance - perhaps at least two times slower than with a proper step size.
The text was updated successfully, but these errors were encountered:
errrm this turns out NOT to be a problem, in fact. Yes, there is a performance penalty for using smaller step sizes: extra bit planes are coded and then possibly discarded in lossy mode. However, the advantage is giving EBCOT more bit planes to work with, resulting in higher PSNR. Closing.
Subband stepsize is always less than one in OpenJPEG. This means that quantization is not taking place: i.e. DWT coefficients are being mapped to a larger dynamic range, rather than a smaller one,
since quantization take place by multiplying coefficients by the reciprocal of the step size.
This is very inefficient. I don't think this is a conformance issue, because encoders are free to choose the quantization step. But, I would guess this situation creates a serious hit in performance - perhaps at least two times slower than with a proper step size.
The text was updated successfully, but these errors were encountered: