- Connecting
- Need
- Answer
Laptop with USB-C to a TV
Get this
USB-C to HDMI cable or adapter that says HDMI 2.0 / 4K 60Hz (HDMI 2.1 / 4K 120Hz for gaming)
Look for
- Laptop port shows a DisplayPort or Thunderbolt icon
- Adapter lists 4K@60Hz, not just 4K
Avoid
- "4K" adapters that are HDMI 1.4 (4K 30 Hz only)
The numbers: 4K 60 Hz 8-bit
| Link | Needs | Has | Result |
|---|---|---|---|
| HDMI 1.4TV timing | 14.26 Gbps | 8.16 Gbps | Too much |
| HDMI 2.0TV timing | 14.26 Gbps | 14.40 Gbps | Fits |
How the numbers are worked out
Reduced-blanking timing (VESA CVT-R2)
3840×2160 active → 3920 × 2222 total pixels per frame
3920 × 2222 × 60 Hz = 522.61 MHz pixel clock
522.61 MHz × 24.0 bits per pixel = 12.54 Gbps
8-bit colour, full RGB/4:4:4: 3 × 8 = 24.0 bits per pixel.
"Has" is the link's usable rate after line coding. DSC is modelled as up to 3:1 compression. Full method.
Standards behind this answer
2014
DisplayPort over USB-C (Alt Mode)
How most USB-C ports send video. The USB-C pairs are handed over to DisplayPort.
- data: USB 2.0 or USB 3 alongside
- video: DP 1.4 (or 2.1) over USB-C
- power: USB PD at the same time
HDMI 2.0
The 4K 60 Hz standard. 18 Gbps, HDR from 2.0a, but not enough for 4K 120.
- data: 18 Gbps
- video: 4K 60 Hz
HDMI 1.4
1080p at any common refresh rate, 4K only at 24–30 Hz. Introduced ARC.
- data: 10.2 Gbps
- video: 4K 30 Hz / 1080p 120 Hz