Join Date: Jul 2008
Location: Maputo, Mozambique
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Hi Mark Henninger, thanks a lot for the news.
Beware that the first HDMI2.1 chipsets will support control-plane signalling features such as VRR and ALLM, but their data-plane bandwidth limit could still be 18Gbps.
Just 4K 120fps doesnt make it a true HDMI2.1 chipset, as there are other two data plane variables missing: chroma sub-sampling and color bit depth.
Beware that the data plane bandwidth requirements of 4K 120fps 8-bit (SDR) 4:2:0 actually fits in the 18Gbps limit of HDMI2.0.
If a source device such as a PC manages to output via HDMI port 4K 120fps 8-bit (SDR) 4:2:0, LG marketing team could call it 4K 120fps, even if its just 8-bit SDR, even if the chipset can only do 18Gbps.
Beware of this trick, as it would be just 8-bit SDR.
Check the math below with different data plane variables combination, that result in different bandwidth requirements on the video transmission chain:
4K @ 120fps @ 8bit per color (not HDR)
3840pixel x 2160pixel x (24bit + 12bit)/pixel x 120frame/second =
35831808000 bits/s = 35.8Gbps @ RGB/Y’CbCr 4:4:4
23887872000 bits/s = 23.8Gbps @ Y’CbCr 4:2:2
17915904000 bits/s = 17.9Gbps @ Y’CbCr 4:2:0 <--- (Beware of this trick, its just 8-bit SDR)
4K @ 120fps @ 10bit per color (HDR)
3840pixel x 2160pixel x (30bit + 15bit)/pixel x 120frame/second =
44789760000 bits/s = 44.8Gbps @ RGB/Y’CbCr 4:4:4
29859840000 bits/s = 29.8Gbps @ Y’CbCr 4:2:2
22394880000 bits/s = 22.4Gbps @ Y’CbCr 4:2:0 <------- Stored Content in HDR 10bit
4K @ 120fps @ 12bit per color (HDR)
3840pixel x 2160pixel x (36bit + 18bit)/pixel x 120frame/second =
53747712000 bits/s = 53.7Gbps @ RGB/Y’CbCr 4:4:4
35831808000 bits/s = 35.8Gbps @ Y’CbCr 4:2:2 <------- What is sent via HDMI, BELOW HDMI2.1 48Gbps limit
26873856000 bits/s = 26.8Gbps @ Y’CbCr 4:2:0
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