[x264-devel] x264 quantization and AIC quastions

[math-BeSSeL at yandex.ru]

Hi, all!
Sorry for my bad English.

I have some questions on x264 realization.

1) For quantization process in the h.264 standard the following formula is used

coef_q = (coef * mf + f)>> (15 + Qp/6) (*)  (for example for intra mb and coef>=0)

In the x264 codec other formula is used 

coef_q" = ((coef + f") * mf")>> 16 (**)

After the certain transformations from one it is possible to receive another: (*) <-> (**). 
But there are conditions when the quantization result of the second formula (**) does not coincide with result of the first formula (*).
Why this formula (**) is used? 
What for a variable "deadzone"?

2) I_PRED_4x4_DC_LEFT / TOP, I_PRED_CHROMA_DC_LEFT / TOP, I_PRED_16x16_DC_LEFT / TOP. 
   I can is wrong, but the given modes are not present in the h.264 standard.