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0 pointsadrian_b1y ago0 comments

What I find very annoying is that a very large number of small computers and laptops have both DisplayPort and HDMI, but they have full-size HDMI connectors and only USB Type C DisplayPort.

Using Type C for DisplayPort instead of the good full-size DisplayPort connectors is less reliable (easy to disconnect accidentally) and it permits only shorter video cables.

More importantly, this blocks the Type C connector, which I need for other purposes, e.g. an external SSD. I do not want to carry a Type C dock, so I end using HDMI, even if I do not need HDMI and I do not want HDMI and even if in almost all cases the devices had enough free space for a full-size DisplayPort connector.

Even replacing the HDMI connector with a DisplayPort connector (so that the devices would have only full-size and Type C DisplayPort) is always a better solution, because there are a lot of cheap adapters from DisplayPort to HDMI, which do not need a separate power supply and they can even be incorporated inside the video cable. The reverse adapters, from HDMI to DisplayPort, are much more expensive and much bulkier, so usually they are not acceptable.

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eqvinox1y ago

> The reverse adapters, from HDMI to DisplayPort, are much more expensive and much bulkier, so usually they are not acceptable.

That's because those are active converters — contrast DisplayPort has "DP++" which means the source port is electrically capable of transmitting either DP or HDMI signals; the graphics card can switch modes. The adapter is a tiny IC to signal doing that switchover and just wires the data lanes through. HDMI has no such thing, you need an active protocol converter IC to get DisplayPort.

(NB: there are also active DP→HDMI converters, they have a bit longer range than the passive ones. I had to use one of them for my home projector, it's on a 10m HDMI cable which only worked on a blue moon with a passive DP++ adapter. Funnily enough it doesn't work on my native HDMI port either, only the active converter gets it running reliably… might be a poor 10m cable ;D)

DP++ wasn't part of the original DP spec, but I don't believe any DP source hardware that doesn't support DP++ is being manufactured at this point.

adrian_bOP1y ago

The DisplayPort connector includes a supply voltage. While it is weaker than in USB, it is strong enough to provide power to an active DisplayPort to HDMI converter, which can have the appearance of a video cable that can connect a DisplayPort source to an HDMI sink.

On one of the HDMI pins there is a DC voltage, but it has other purposes and it is too weak to provide power for a video converter.

This is why an HDMI to DisplayPort converter always requires an additional external power supply.

shiroiushi1y ago

It seems the issue with this open-source driver is supporting some of the highest-performance modes of HDMI (like 4K @ 120Hz). Would that even work in a DisplayPort-to-HDMI adapter?

adrian_bOP1y ago

While there are no fundamental reasons for any video mode to not work, most of the DisplayPort to HDMI adapters that are currently on the market do not support the latest standard versions of DisplayPort and/or HDMI, so when a very high performance mode is desired, it might not work.

However, the main use of adapters is when you travel and you find in your temporary office an HDMI-only monitor, or when you must use a meeting room projector. Such monitors or projectors seldom support high performance video modes.

account421y ago

A problem is also that many video cards that do support HDMI 2.1 only support display port DisplayPort 1.4 which has less bandwith. This makes the sitution with the open source AMD drivers even more annoying because even with an active adapter that supports all the required features (which most don't) you can't get the full HDMI 2.1 resolutions/refresh rates that way.

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0 pointsadrian_b1y ago0 comments

What I find very annoying is that a very large number of small computers and laptops have both DisplayPort and HDMI, but they have full-size HDMI connectors and only USB Type C DisplayPort.

Using Type C for DisplayPort instead of the good full-size DisplayPort connectors is less reliable (easy to disconnect accidentally) and it permits only shorter video cables.

0 comments

eqvinox1y ago

> The reverse adapters, from HDMI to DisplayPort, are much more expensive and much bulkier, so usually they are not acceptable.

DP++ wasn't part of the original DP spec, but I don't believe any DP source hardware that doesn't support DP++ is being manufactured at this point.

adrian_bOP1y ago

On one of the HDMI pins there is a DC voltage, but it has other purposes and it is too weak to provide power for a video converter.

This is why an HDMI to DisplayPort converter always requires an additional external power supply.

shiroiushi1y ago

It seems the issue with this open-source driver is supporting some of the highest-performance modes of HDMI (like 4K @ 120Hz). Would that even work in a DisplayPort-to-HDMI adapter?

adrian_bOP1y ago

account421y ago

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