When watching speedrunners playing old console games, and even newer ones, it might be a bit surprising that many of them prefer a good old-fashioned chunky CRT TV over a modern LCD/LED TV (even though many of the latter support composite input, or in the worst case scenario, there exist converters).
Many people who don't know the reason might be a bit surprised by the reason: Input lag.
CRT TVs have essentially no input lag whatsoever. This means that the console is perfectly "in sync" with the cathode ray of the TV, ie. anything that the console is outputting for the current scanline is immediately shown on screen. The longest possible lag between eg. a controller button press and its effect happening on screen is 1/60th of a second (or 1/50th in the case of PAL), because that's how long the refreshing of the screen takes. This is more than sufficient for human reflexes (eg. in speedrunning).
This implies that LCD/LED TVs have some kind of input lag. That's often the case. Depending on the particular brand and model of TV, this input lag can vary all the way from one entire frame to half a dozen frames.
Modern TVs typically perform all kinds of post-processing to the image they are receiving for display. They might perform brightness/contrast adjustments, color correction, noise reduction, and all sorts of things. They buffer the input video signal they are taking, and perform these operations on the individual buffered images before displaying them. In some cases this might take several frames. (In other words, the image you are seeing might have been sent via the HDMI or whatever cable to it several frames prior, meaning something like 3/60ths or 4/60ths of a second ago.)
When watching TV or a DVD/BluRay this doesn't make any difference. It really doesn't matter if the BluRay player sent it the picture eg. 3/60ths of a second prior. It's impossible to even notice.
However, it can become noticeable when the TV is used to play a console game (or sometimes even a PC game). The more lag there is between you pressing a controller button, and its effect happening on screen, the more noticeable it becomes. For power-players (such as speedrunners and many online gamers) this input lag may be crucial. The better your reflexes are in a given game, the more you notice the input lag, and the more it hinders your gameplay.
Computer displays, even though in the modern day they use pretty much identical technology to TVs, generally eschew any such post-processing and display images as soon as they get it (meaning that the input lag is, optimally, at most that 1/60th of a second. Or even less if the display has a higher refresh rate.)
This is where the so-called "game mode" of many modern TVs comes in. Many people don't know what it means, and might think it's just a mode that adjusts brightness, contrast, color correction and other such things for games to look better (at least in the manufacturer's opinion). However, what it usually means is that the TV forgoes most of its post-processing steps in order to display the input image as soon as possible, reducing input lag.
With some TVs this might mean that it, for example, reduces the lag from something like 4/60ths of a second to just 2/60ths. A few TVs might even reach the computer monitor speed of 1/60ths of a second.
If you play with a console using a TV, it's recommended to use the "game mode" setting of the TV, if it has one, so that games will become more "responsive", without that input lag (or, at least, with a minimized input lag).
Thursday, September 28, 2017
Sunday, September 3, 2017
HDMI 2.0 switcher/splitter purchasing guide
If you own a PS4 Pro and an HDMI 2.0 capable 4k display, especially if said display has only one HDMI in port, you may soon find yourself in need of an HDMI switcher. If you are additionally using a PSVR with your PS4 Pro, you might also find yourself in need of an HDMI splitter, or switcher/splitter combo (for reasons detailed in this blog post.)
Due to the different versions that exist of the HDMI standard, this is prone to cause confusion, and for people to purchase a switcher that won't work properly with their PS4 Pro. So here is a guide that describes in detail what to look for.
An HDMI switcher is a device that has two or more HDMI inputs and one HDMI output, and is capable of redirecting one of those inputs to the output. This allows several HDMI sources (such as game consoles, a digital TV box, and a PC) to be connected to one single display.
An HDMI splitter is a device that has one HDMI input and two or more HDMI outputs. It allows for the image of a single HDMI source device to be redirected to several displays (possibly simultaneously).
Some devices are both, having multiple inputs and outputs. This is often denoted as (although the notation is not standardized) for example "3x1" for switchers (3 inputs, one output), "1x3" for splitters (one input, three outputs), and eg. "6x2" for devices supporting both (6 inputs, 2 outputs). Usually the latter allows for any two of the inputs to be redirected to the two outputs simultaneously. (Note that in some cases the "3x1" form may also be used for splitters. The notation is not always consistent.) Other devices are bi-directional, which means that they can be used as a switcher or a splitter (but not both at the same time, since they have only one port that functions as an input or an output, the others functioning as the opposite).
HDMI 1.3 and older only supports Full-HD resolutions, in other words, 1920x1080 pixels. It's completely unusable for 4k material.
HDMI 1.4 supports Full-HD video at 120 Hz, as well as 4k video (3840x2160) at 30 Hz. It has a bandwidth of 10.2 Gbps.
HDMI 2.0 supports 4k video at 60 Hz. It has a bandwidth of 18 Gbps.
Note that the PS4 Pro supports displaying 4k video at 60 Hz over an HDMI 1.4 connection, but only in YUV420 mode rather than RGB mode (if the display supports this). However, as far as I understand, this is a non-standard extension. YUV420 compromises image quality by reducing color information (in order to be able for the image to be transmitted at 10.2 Gbps.) RGB mode has no such compromise.
As of writing this post, switchers and splitters having full HDMI 2.0 support are still a rarity, and a user may be fooled into buying a device with no such support, only to find out that the PS4 Pro has switched to YUV420 mode or, in the worst case scenario, can't display an image at all (which is sadly common). Thus a potential buyer needs to be very careful when purchasing such a device.
Important note: Even if a switcher/splitter mentions "HDMI 2.0" support, this is not a guarantee that it will work properly with the PS4 Pro!
There are some such devices out there that mention such support, but still internally have a bandwidth of 10.2 Gbps (ie. the one from HDMI 1.4). If you try to use this kind of switcher/splitter with the PS4 Pro, you'll probably find out that the console will be limited to YUV420 mode (or, possibly, not being able to display anything at all)! I do not know how these manufacturers can make the claim of HDMI 2.0 support for these devices, but I'm assuming they support everything else in the standard except for the 18 Gbps bandwidth.
It's more important to look in the specifications of the device for a mention of support for 4k resolutions at 60 Hz. This may be expressed for example as "3840x2160@60Hz", or sometimes as "4Kx2K@60Hz".
If the specs for the device say "3820x2160@30Hz", or "4Kx2K@30Hz", or explicitly "HDMI 1.4" (often "HDMI 1.4b"), then it does not have HDMI 2.0 support. Avoid these.
Be wary of switchers/splitters that do not mention at all a refresh rate for the 4k resolution, nor a HDMI version. A mention of "4k" alone is not enough, and lacking the refresh rate is an almost sure sign that it's an HDMI 1.4 device.
Also, as mentioned, be careful with devices that do mention "HDMI 2.0" but not a refresh rate for the 4k resolution. These might or might not support the necessary bandwidth of 18 Gbps.
"How do I know if the PS4 Pro is using RGB or YUV420 mode?"
The PS4 system might not always make it completely clear which mode is being currently used, and whether 2160p RGB is supported. However, if you go to the system settings, choose "display and sound", and from there "video output settings" and "resolution", the "2160p - RGB (Unsupported)" line will be grayed out if using HDMI 1.4.
Due to the different versions that exist of the HDMI standard, this is prone to cause confusion, and for people to purchase a switcher that won't work properly with their PS4 Pro. So here is a guide that describes in detail what to look for.
Terminology and HDMI versions
An HDMI switcher is a device that has two or more HDMI inputs and one HDMI output, and is capable of redirecting one of those inputs to the output. This allows several HDMI sources (such as game consoles, a digital TV box, and a PC) to be connected to one single display.
An HDMI splitter is a device that has one HDMI input and two or more HDMI outputs. It allows for the image of a single HDMI source device to be redirected to several displays (possibly simultaneously).
Some devices are both, having multiple inputs and outputs. This is often denoted as (although the notation is not standardized) for example "3x1" for switchers (3 inputs, one output), "1x3" for splitters (one input, three outputs), and eg. "6x2" for devices supporting both (6 inputs, 2 outputs). Usually the latter allows for any two of the inputs to be redirected to the two outputs simultaneously. (Note that in some cases the "3x1" form may also be used for splitters. The notation is not always consistent.) Other devices are bi-directional, which means that they can be used as a switcher or a splitter (but not both at the same time, since they have only one port that functions as an input or an output, the others functioning as the opposite).
HDMI 1.3 and older only supports Full-HD resolutions, in other words, 1920x1080 pixels. It's completely unusable for 4k material.
HDMI 1.4 supports Full-HD video at 120 Hz, as well as 4k video (3840x2160) at 30 Hz. It has a bandwidth of 10.2 Gbps.
HDMI 2.0 supports 4k video at 60 Hz. It has a bandwidth of 18 Gbps.
Note that the PS4 Pro supports displaying 4k video at 60 Hz over an HDMI 1.4 connection, but only in YUV420 mode rather than RGB mode (if the display supports this). However, as far as I understand, this is a non-standard extension. YUV420 compromises image quality by reducing color information (in order to be able for the image to be transmitted at 10.2 Gbps.) RGB mode has no such compromise.
What to look for when purchasing an HDMI switcher/splitter
As of writing this post, switchers and splitters having full HDMI 2.0 support are still a rarity, and a user may be fooled into buying a device with no such support, only to find out that the PS4 Pro has switched to YUV420 mode or, in the worst case scenario, can't display an image at all (which is sadly common). Thus a potential buyer needs to be very careful when purchasing such a device.
Important note: Even if a switcher/splitter mentions "HDMI 2.0" support, this is not a guarantee that it will work properly with the PS4 Pro!
There are some such devices out there that mention such support, but still internally have a bandwidth of 10.2 Gbps (ie. the one from HDMI 1.4). If you try to use this kind of switcher/splitter with the PS4 Pro, you'll probably find out that the console will be limited to YUV420 mode (or, possibly, not being able to display anything at all)! I do not know how these manufacturers can make the claim of HDMI 2.0 support for these devices, but I'm assuming they support everything else in the standard except for the 18 Gbps bandwidth.
It's more important to look in the specifications of the device for a mention of support for 4k resolutions at 60 Hz. This may be expressed for example as "3840x2160@60Hz", or sometimes as "4Kx2K@60Hz".
If the specs for the device say "3820x2160@30Hz", or "4Kx2K@30Hz", or explicitly "HDMI 1.4" (often "HDMI 1.4b"), then it does not have HDMI 2.0 support. Avoid these.
Be wary of switchers/splitters that do not mention at all a refresh rate for the 4k resolution, nor a HDMI version. A mention of "4k" alone is not enough, and lacking the refresh rate is an almost sure sign that it's an HDMI 1.4 device.
Also, as mentioned, be careful with devices that do mention "HDMI 2.0" but not a refresh rate for the 4k resolution. These might or might not support the necessary bandwidth of 18 Gbps.
"How do I know if the PS4 Pro is using RGB or YUV420 mode?"
The PS4 system might not always make it completely clear which mode is being currently used, and whether 2160p RGB is supported. However, if you go to the system settings, choose "display and sound", and from there "video output settings" and "resolution", the "2160p - RGB (Unsupported)" line will be grayed out if using HDMI 1.4.
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