TV connectivity round-up

Written on 2 December 2017, 09:33pm

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A short reminder about the ins and outs (pun intended) of the nowadays TV sets and their connected peripherals.

HDMI 1.4 vs 2.0

Official specifications of the HDMI 2.0 standard:

* Enables transmission of High Dynamic Range (HDR) video
* Bandwidth up to 18Gbps
* 4K@50/60 (2160p)
HDMI 2.0b does not define new cables or new connectors. Current High Speed cables (Category 2 cables) are capable of carrying the increased bandwidth.
The newer HDMI 2.1 specifications add support for a range of higher video resolutions and refresh rates including 8K60 and 4K120, and resolutions up to 10K. Dynamic HDR formats are also supported, and bandwidth capability is increased up to 48Gbps.

Two notes:
1. HDMI 2.0 is a hardware update, and both ends must have a HDMI 2.0 compatible chipset
2. In order to enjoy the benefits of the HDMI 2.0, the HDMI cable must be able to sustain the 18Gbps bandwidth
See more in the troubleshooting section below.

What do ARC and MHL mean?

On the back of your TV set, next to the HDMI ports you will see these 2 labels:
ARC – Audio Return Channel – enables the TV to send the audio data to the receiver. All HDMI cables support ARC by default; for TV and receivers compatibility look for the port label and/or user manual. Even if the TV has all the HDMI ports ARC-compatible, only one of them will be used at a time.
MHL – Mobile High Definition Link – allows to connect and mirror smartphones and tablets (both Android and iOS) to the TV.
On some TV sets you might also see HDCP (High-bandwidth Digital Content Protection) which implements a form of digital copy protection.

HDR standards: HDR10 vs Dolby Vision

You know how virtually all the TV producers brag about their newest models being HDR? Well, there are more standards that apply: HDR10, HDR10+, Dolby Vision, Hybrid Log-Gamma, SL-HDR1, etc.
For instance, Apple TV 4K supports the following standards:

4K Standard Dynamic Range (SDR): Used for 4K televisions that don’t support HDR10 or Dolby Vision.
4K High Dynamic Range (HDR, aka HDR10): Used for 4K televisions that support HDR to display video with a broader range of colors and luminance.
4K Dolby Vision: Used for 4K televisions that support Dolby Vision HDR to display video with a broader range of colors and luminance optimized for your television.

To see which HDR standard your TV supports, look at the fine print in the user manual (they should also indicate which HDMI port supports these HDR standards):

4:2:2? 4:2:0?

Here things become a bit more complex. If you’re not interested in the details, remember just that the higher the 3 numbers above, the better. As Apple says in the Apple TV 4K menu, “4:2:0 provides high-quality picture that is compatible with most TVs and HDMI cables. 4:2:2 improves quality, but requires high-speed cables“.

There’s a tradeoff between video quality and bandwidth. With 4K resolutions, 60Hz refresh rates, full 36-bit color depth, HDR capabilities and 32 audio channels, the bandwidth can reach incredible numbers. And as we saw above, HDMI 2.0 is limited to 18Gbps (48Gbps in HDMI 2.1). The solution is to compress the video signal exploiting the limitations of the human eye.
To make the explanation simpler, meet Chroma and Luma:

Chroma is the signal used in video systems to convey the color information
Luma represents the brightness in an image
Digital signals are often compressed. Since the human visual system is much more sensitive to variations in brightness than color, a video system can be optimized by devoting more bandwidth to the luma component (Y’, brightness), than to the color (Cb, Cr).

Below you can see how the original image is de-composed in Luma component (black and white – brightness only) and Chroma (color). The Luma is un-altered, but the Chroma is compressed (except for 4:4:4). Depending on the compression type, you can have 4:2:2, 4:2:0 or other subsampling systems (no 4-4-2 system though 🙂 ):

The bandwidth savings are impressive: the 4:2:2 sampling can reduce the necessary bandwidth to 12Gbps, while 4:2:0 further drops the requirement to 9Gbps.

Troubleshooting guide

Knowing all this, if you still have trouble getting the most of your peripherals and TV, here is a quick troubleshooting guide:
– can’t select 4:2:2 chroma: HDMI 2.0 supports 4:2:0 natively, but in order to benefit from 4:2:2 you have to upgrade your HDMI cable. Here is a decent one: Belkin Ultra High speed
– can’t select 4K HDR @60Hz: check your HDMI connectors, some manufacturers only accept HDR on HDMI1 and HDMI2 ports.
– my TV says it’s HDMI 2.0, but it’s not: well, it might be that only the port HDMI1 supports HDMI 2.0, while the others only support HDMI 1.4. That’s sad, but it can happen to older TV sets; just read the manual
– my TV won’t turn on/off when I turn on/off my peripherals: make sure you enable CEC in your TV menu. It can be named differently depending on the TV manufacturer: Bravia Sync for Sony, Anynet+ for Samsung, VIERA Link for Panasonic, EasyLink for Philips, SimpLink for LG.
– I can’t control the sound of my TV from my Apple TV remote: make your Apple TV ‘learn’ the TV remote.
– …but I have a Sonos Playbar linked to my TV: then go to your Sonos settings and pair your Sonos system with the Apple TV remote. However, be aware that a single remote can be paired with the Sonos system.