HDMI Alt Mode for USB Type-C Connector • Hacker News Board

Re: HDMI Alt Mode for USB Type-C Connector

#51

Post by Fatnino » Sun, May 21, 2023, 11:11 AM UTC

seba_dos1 wrote: post #50

usernew wrote: post #47

Earlier quoted context omitted.

I'm not addressing the Alt-mode. Please read what was written, and reply to what was written. The comment to which I replied said you connect devices with display port, not HDMI, because all your devices are monitors. The real-world use case is USB-C to HDMI, to connect to a TV. I have no idea what my cables do, but they have USB-C on one end, and HDMI, not DP on the other, and I plug them into the TV. The comment st…

You seem pretty confused. > From a quick google, the reason Alt mode is "dead" is because most devices natively support HDMI and you don't need alt-mode. If you do video over USB-C, you need alt-mode. Everything uses DisplayPort alt-mode and converts it to HDMI if needed. These days most devices have no other form of video connectivity than USB-C. You link to an article that literally states "DisplayPort has won". >…

I recently picked up a $100 external display on amazon. It's essentially a laptop screen with a magnetic cover a la surface tablet.

It's just a screen, no touch capabilities or any real processing onboard.

This screen has 3 usbc ports and a mini hdmi port. It also has an audio out jack.

In theory, it can be driven with a usbc to usbc cable from a phone or computer, but I don't have a device that can drive it this way.

The second usbc port is auxiliary power for when your phone can't power the whole screen.

The third usbc port is for daisy chaining another device.

The way I use this thing is from my (fairly old) laptop that only has display port out. I have an adapter that changes the DP port on my laptop to full side hdmi and then use the hdmi to hdmi mini cable that came with the screen.

Unfortunately, this setup does not pass sound to the audio jack. I wish my laptop had an hdmi port instead.

Re: HDMI Alt Mode for USB Type-C Connector

#52

Post by seba_dos1 » Sun, May 21, 2023, 12:45 PM UTC

Fatnino wrote: post #51

seba_dos1 wrote: post #50

Earlier quoted context omitted.

You seem pretty confused. > From a quick google, the reason Alt mode is "dead" is because most devices natively support HDMI and you don't need alt-mode. If you do video over USB-C, you need alt-mode. Everything uses DisplayPort alt-mode and converts it to HDMI if needed. These days most devices have no other form of video connectivity than USB-C. You link to an article that literally states "DisplayPort has won". >…

I recently picked up a $100 external display on amazon. It's essentially a laptop screen with a magnetic cover a la surface tablet. It's just a screen, no touch capabilities or any real processing onboard. This screen has 3 usbc ports and a mini hdmi port. It also has an audio out jack. In theory, it can be driven with a usbc to usbc cable from a phone or computer, but I don't have a device that can drive it this way…

I have a similar portable screen with almost the same set connectors (only two USB-C ports and miniHDMI, no daisy chaining). That "(fairly old)" is the key there, as pretty much all modern laptops support DisplayPort over USB-C. I can plug that screen to my 4 year old laptop or my phone using USB-C to USB-C cable and it works, including audio.

Re: HDMI Alt Mode for USB Type-C Connector

#53

Post by startupsfail » Mon, May 22, 2023, 4:19 PM UTC

pornel wrote: post #15

startupsfail wrote: post #11

USB Type-C is such a mistake for video connectivity. It just doesn’t work most of the time and when it works, any tiny move of the USB Type-C cable breaks it down.

I use USB-C-to-DP cables as well as full Thunderbolt and haven’t had issues with them. USB-C cables can be garbage, so you probably need to get a better one.

Well, here is one example. I use the cables that came with the portable monitor. When I use a miniHDMI cable, no problems. With USB-C the monitor drops the connection and blinks every so often.

Here is another example. A coworker came crying that her monitor is dropping connection. We’ve tried an HDMI cable (this is a full size monitor connected to a laptop), problem disappears.

It’s a difference between working reliably (like an HDMI cable) vs working sometimes, if you are lucky.