 NV12

NV12 is an eight-bit YCbCr semiplanar pixel format with 4:2:0 chroma subsampling. A full-resolution plane holds luma samples. The following plane stores alternating Cb and Cr samples, with half as many sample positions in each spatial direction. Linux specifies ordinary untiled NV12 with adjacent planes; the separately allocated variant is NV12M.^[ref]

For even dimensions $W,H$, active samples occupy $WH$ luma bytes plus $WH/2$ interleaved colour-difference bytes. This is $3WH/2$ bytes, or an average of 12 bits per original pixel. It does not give every pixel its own three-component triple: neighbouring pixels share the lower-resolution colour-difference samples.

For an original address calculation, choose width six, height four and an eight-byte framebuffer stride in both planes. Put the first luma row at address 1000. The luma allocation occupies $4(8)=32$ bytes, so the colour-difference plane starts at 1032 and occupies another $2(8)=16$ bytes. There are 36 active bytes in 48 allocated bytes, including row padding.

With zero-based indices, luma position $(r,c)=(3,5)$ is at $1000+3(8)+5=1029$. Its associated subsampled grid cell has indices $(\lfloor r/2\rfloor ,\lfloor c/2\rfloor )=(1,2)$ in this declared layout. That cell's Cb and Cr bytes are at 1044 and 1045. Colour reconstruction additionally needs a sampling-location and filtering convention; these address calculations alone do not specify it.

The pixel format identifies storage. A decoder must also know the YCbCr matrix and code ranges to interpret the numbers as colour.