movmasty
30th April 2007, 03:53
We know that in the intra it is greyed with value 8, in the inter matrix it is not, but is not clear if you can go under 16 or even under 8.
as i have understood this is related to the bit deept of quantization process, that with an input of 12 bit(yu12 colourspace) and a range of possible output values of 9 bits(8 and one for the signs + , -), needs a minumum divisor of 3 bit(8), that is the upper left value at quantizer 1,
dont know if the inter matrix has an input of 12 bits too.
this prevent us to have totally customized matrices
To turn around this, would be enough to hardcode set the min quant to 2, thus allowing the upper left value to be set as low as 4, and however to any value over 4 that you need.
Moreove you always get Q 1 that would be 2 with 4 at the upper left.
as i have understood this is related to the bit deept of quantization process, that with an input of 12 bit(yu12 colourspace) and a range of possible output values of 9 bits(8 and one for the signs + , -), needs a minumum divisor of 3 bit(8), that is the upper left value at quantizer 1,
dont know if the inter matrix has an input of 12 bits too.
this prevent us to have totally customized matrices
To turn around this, would be enough to hardcode set the min quant to 2, thus allowing the upper left value to be set as low as 4, and however to any value over 4 that you need.
Moreove you always get Q 1 that would be 2 with 4 at the upper left.