Diary Of An x264 Developer

06/03/2008 (11:03 am)

The power of CABAC

Filed under: CABAC,H.264,rate-distortion optimization ::

Today we’ll take a post directly from the stream analyzer.

position : 24×25 (384×400)
mb_addr : 1024
size (in bits) : 1
mb_type : 1
pmode : 0
mb_type : Intra(I_16x16_0_0_0)
slice_number : 0
transform_8x8 : 0
field\frame : frame
cbp bits
: 0000 00 00
: 0000 00 00
: 0000
: 0000
quant_param : 0
pmode : Intra_16x16
ipred : 16x16_Vertical

position : 23×27 (368×432)
mb_addr : 1103
size (in bits) : 15
mb_type : 6
pmode : 0
mb_type : Intra(I_16x16_0_0_0)
slice_number : 0
transform_8x8 : 0
field\frame : frame
cbp bits
: 0000 00 00
: 0000 00 00
: 0000
: 0000
quant_param : 0
pmode : Intra_16x16
ipred : 16x16_Vertical

Same macroblock type. Same (zero) coded block pattern. Same prediction mode. Except that one is 1 bit, and the other is 15.  Both are CABAC; the only different is the state of the context table.