Tong Family (richtong.org sync)

OK, we want to get a bunch of machines to really work well with the latest monitors at the highest resolution, HDR and refresh rates. Turns out it is quite a trick so here are some quick notes. I’ve been wrestling with this for the last five years to get the nirvana of 4K@120Hz HDR10 at 4:4:4 and we are nearly there (before I got to 4K with 10 bpc and 4:2:0)

Macbook Air M5 to LG B9 at 4K HDR 120 Hertz via CalDigit Thunderbolt 4 dock via CableMatter USB C to HDMI with new firmware

This was perhaps the trickiest of all. Even though I’ve the B9 for 7 years, it is still an amazing monitor and for a long time it’s had 120 Hertz support, but I could never get the MacBook Pro M1 Max to support it nor the MacBook Pro M4 (stolen!), but finally got it to work with a firmware upgrade to the CableMatters USB C to HDMI adapter.

This is a painful update that requires you find a Windows machine, then download a sketchy piece of firmware updater and then flash the USB C to HDMI adapter. Then voila, it only works with the Mac, but it supports the full HDMI 2.1 with HDR and 120 Hertz.

The issues have been multi-year. First is that the MacBook Pro initial M1 family were hard limited to HDMI 2.0 rates so you could get HDR but not 120 Hertz. I finally got it to work by plugging it directly into the MacBook Pro port.

Fortunately with the M5 MacBook Air, the firmware in Tahoe can handle the 120 Hertz HDR at 4K, but the adapter does not and has to be flashed

1. MacBook Air M5. This now supports with Tahoe running with 4K HDR at 120 Hertz. The limitation has to do with HDMI 2.0 vs HDMI 2.1. The old drivers only supported HDMI 2.0 bandwidth which enough for HDR but not for 120 Hertz.
2. Cable Matters USB C to 8K HDMI Adapter. (Models 201388 or 201361)The problem is that the adapters that take you from there don’t work, you need to flash the Synaptics driver on them with a Windows application no less. Or you can buy a pre-flashed one. The deep answer is that the is the Synaptics VMM7100 chipset inside the Cable Matter adapter.
3. Cable Matters DisplayPort to HDMI adapter (102101) that can also be flashed as well but you can’t use DisplayPort 1.4 (eg the CalDigit Thunderbolt 3 is 1.4 with 32Gbps and only does 60 hertz but the CalDigit Thunderbolt 4 is DisplayPort 2.0 which is 80Gbps and can support obviously way more. Unfortunately I don’t have on of these around I do have

Note that this setup should theoretically also work with the MacBook Pro M1 Max, but I’ve not tried it (mainly because this is the only device I have which supports 5 monitors)

Macbook Neo to Sony at 4K HDR 60 Hertz via Razer Thunderbolt 4 dock

In fact, the Neo does not use Thunderbolt at all, it is a USB C device and can ly support 4K HDR at 60 hertz. There are a few tricks:

1. Only one USB 3 port. the MacBook Neo closest to the screen port USB is USB 3, but the lower port is just USB 2 (so good for charging). MacBook. The USB 3.0 port is 10Gbps and the USB 2.0 port is 480 Mbpsband

Using the Screen Bandwidth Calculator

This is an incredibly confusing area, but the Bandwidth Calculator is really handly for this, the thing to remember is that different standards have different bandwidth and that with converts say from USB C to HDMI 2.0, you have to have enugh bandwidth in both, so here are the requirements for different outputs

And here is what can be supported. Note that in nearly all cases color compression (aka color subsampling works OK with modern monitors):

Resolution	Refresh Rate	Color Depth	Chroma Subsampling	Bandwidth
3840×2160	60 Hz	8-bit SDR	4:2:2	8Gbps
3840×2160	60	8-bit SDR	4:4:4	12Gbps
3840×2160	60	10-bit HDR10	4:4:4	15Gbps
3840×2160	120	8-bit SDR	4:4:4	26Gbps
3840×2160	120	10-bit HDR	4:4:4	30Gbps

Type	Bandwidth	Max Resolution/HDR/Chroma
USB 2.0	480 Mbps	N/A
USB 3.0 Type 1	5 Gbps	N/A
USB 3.0 Type 2	10 Gbps	4K@60 HDR10 4:2:2
USB 4.0	40 Gbps	4K@120 12-bit 4:4:4
Thunderbolt 3	40 Gbps (1 meter or less)/ 20Gbps	4K@120 12-bit 4:4:4
Thunderbolt 4	40 Gbps (2 meter)	4K@120 12-bit 4:4:4
Thunderbolt 5	80Gbps	4K@240 12-bit 4:4:4
HDMI 1.4	10.2 Gbps	4K@60 HDR10 4:2;2
HDMI 2.0	18 Gbps	4K@60Hz HDR10
HDMI 2.1	48 Gbps	4K@120Hz HDR10+
DisplayPort 1.2	17.28 Gbps	4K@60Hz
DisplayPort 1.4	25.92 Gbps	4K@120Hz HDR
DisplayPort 2.0	77.37 Gbps	8K@60Hz HDR10+

How do figure out what you are running

One of the big questions is what resolutions, chroma subsampling and frequency are you running some are easy:

1. On your Mac in Displays, you should see the resolutions
2. You know you are in HDR (that is at least 10 bit color) if a HDR button appears in the Display pane

But in general it is very hard to know what is exactly being sent because System Information used to provide this but not anymore, but it looks like BetterDisplay is your friend. I’ve used a bunch of these like the resolution finder, but this tells you want is running, just click on BetterDisplay > Display > Export Display Information and it has for example with an ASUS PB278Q and Acer XB270HU. Note that it is a confusing application, to see the Color sampling, you have to click on the little App Menu at the bottom to see it.

1. Date of Manufacture. Sort of interesting to see I have monitors that are over 10 years old. Built in 2014? (the Acer has no Year of manufacture)
2. Supports HDR. I don’t think this is true, but it says our ASUS PB278 support HDR? I don’t think so and specs confirm they are SDR only and have a native 8-bit Panel (eg SDR is 8 bits per color plane)
3. Logical Width and Height. Such as 2560×1440 for WQHD resolution monitors that are PLS.
4. Refresh string: 60 Hertz aka Max refresh rate
5. App Menu > _Display_ > Color Mode or by clicking on the Menubar icon for Better Displays. It’s not really clear where the Chroma subsampling figure is in all this by looking at their wiki which devin allow searching for this but finds no mentions. Apparently this is related to if you are using YCbCr or RGB mode. YOu can use the service menu of your display to get it into RGB mode. Or you can try an on-screen test. Note that Blu-ray uses 4:2:0 but you want 4:4:4 for most displays. On LG and Samsung, if you set the mode to “PC” on th input, it will use 4:4:4 but other modes use 4:2:2 and you can use DSC (Digital Stream Compression) instead of these color tricks. There is a test for this, but it looks the same to me. It might require some EDID edits as well which sounds very scary. But for a 1440p monitor I get “SDR RGB Full Range”

The there is a Current Display Mode at the connection level so things liek:

1. Dimensions: 2550×1440
2. Refresh rate: 59.949999 for the ASUS and 119.9999997 for the Acer
3. Variable Refresh Rate: No
4. Bit depth: 8 bit per sample
5. Color Mode; RGB Full Range (some of these clip off the end colors)
6. HDR/SDR Mode: SDR

MacBook Pro M1 Max with 2x ASUS PB278, Acer XB270HU on 2x CalDigit Thunderbolt 3

This is the trickiest configuration. The machine is old of course but because it is basically two M1 Pro’s stapled together, it has double the drive ability. I have found that this configuration is pretty unreliable so here are the notes:

1. You can’t daisy chain the CalDigit Thunderbolt 3 Docks, they need to be plugged into two separate THunderbolt 3 ports. If you do daisy chain, then you lose the use of one of the DisplayPort 1.2 ports
2. On display slep, one or more of the monitors will not wake up. The easy solution is to open the Settings > Display > Arrange and just move the sleeping monitor on and it will usually light up. Otherwise you have to disconnect and reconnect the Thunderbolt connection. And occasionally a power cycle of the monitor can also work.

Here is how to actually configure these:

1. Thunderbolt 3 by Caldigit only has a single downstream Thunderbolt 3 as it is designed for daisy chaining. This also means the 40Gbps is shared and I found that with daisy chaining, I could get the first DisplayPort working and the USB C to HDMI connector on the downstream device, but the downstream DisplayPort.
2. These devices are 120 Hertz 1440p devices or 2560×1440 devices at the base for ACer and 60 Hertz for the ASUS and they are all SDR (8 bits per pixel).
3. Note that you need therefore need both CalDigits plugged directly into the Thunderbolt ports
4. That also the displays will not always wakeup properly when you startup or reconnect or come back from sleep, so what you need to do this is Settings > Displays > Arrange will often bring the sleeping display back if you just move the sleeping display aroound

MacBook Neo to Razer Thunderbolt 4 docks to Sony KD-43X85J 4K monitor

This is another interesting configuration where we want to be able to slide the MacBook Neo or for the MacBook Air M5 or the MacBook Pro M1 Max, so it has a Thunderbolt 4 dock even though the MacBook Neo only uses 10Gbps USB C in the port that’s nearest the screen.

So given this, what is available, this is a Sony 4K TV and you can actually get 4K HDR10 at 60 Hertz for a 2021 Sony Model which Better Display says it’s a X85J model KD-43X85J with HDR10, HLF and Dolby Vision with a Native 120 Hertz with VRR on HDMI 3 and 4. So this works well but you can also see that it works well even with only 10Gbps, which is kind of amazing.

But the nice thing is that if you plug in an MacBook Air M5 or MacBook Pro M1 Pro Max, you should get able to get the full 120 Hertz with 4:4:4 hopefully.

Resolution	Refresh Rate	Color Depth	Chroma Subsampling	Bandwidth
3840×2160	60 Hz	12-bit HDR	4:2:2	10Gbps
3840×2160	120 Hz	12-bit HDR	4:4:4	35Gbps

MacBook Air M5 with LG B9 through CalDigit Thunderbolt 4 dock at 4K HDR at 120 Hz

This is another example of taking advantage of the most machines have to offer. In this case, the MacBook Air cannot handle four displays (unlike the MacBook Pro M1 Max), but connected this way you can get the full capability of the LG

The only question is can the MacBook Air M5 handle the full uncompressed ouitput with HDR10+ and it looks like with BetterDisplays we get the same 16-bit numbering which implies it is running at the full 35Gbps needed for full Chroma. Also the M5 supports full DSC compession so you can get native DisplayPort 1.4 up to HBR3.

Note that with the LG B9, we are not using DisplayPort 1.4, but HDMI 2.1 as input, but this is useful for computer displays

DisplayPort 1.4 Feature	Capability	Components needed
HBR3	8.1Gbps/lane or 32.4Gbps over four	Source, signal path and display need to support
DSC	Lossless datastream compression	Source and display
HDR	HDr meta data	Source, GPU, display
FEC	Forward error correction	Link
MST	Multiple streams on a single oink	Source, hub and display

So for an HDMI 2.1 display like the B9 or the Sony we have:

HDMI 2.1 Feature	Capability	Components support
Premium HDR Cable	18Gbps	Display, Cable, Source
Ultra High HDMI Cable	48Gbps	Display Cable Source
HDR	Dolby Vision, HDR 10+
VRR	Variable Refresh Rate	Display, Computer

HDR demystified

Well I think I already did a post about this but High Dynamic Range is very confusing, so here’s the summary. There is a difference between what a panel supports: 8 bit per pixel (which is SDR) and a true 10-bit per pixel panel (HDR) but there is also 8-bit plus Frame Rate Control which simulates 10-bit on an 8-bit panel. Note that if you send 12 or 16-bits to a monitor, the physical monitors usually only support 10-bit. Paying for a 12-bit is going to cost you alot of money so maybe $7K for a 55″ monitor.

Then there is the actual encoding from source content (like a movie) and there are so many different types:

1. HDR10. This was the first one and it features static data and it is mastered at a particular maximum brightness. Normal SDR is typically 200 nits. But you can master at 600, 1000 and 4000 nits. When a monitor gets this kind of input, it’s linear and then at a certain point, you get a roll off to the TV’s peak brightness so tone mapping is mapping the HDR10 content (that is compressing the brights).
2. Dolby Vision: This uses dynamic metdata so that if you only have say a few highs at 4000 nits, you canray just change the scaling and get more color detail. There are color profiles so 4K Blu-ray uses Profile 7 with different enhancement.
3. HDR10+. This is like Dolby Vision (but you don’t have to pay the Dolby licensing fee) and has dynamic data.