TV isn’t getting a signal from my devices when using USB-C to HDMI
December 25, 2023 5:12 PM Subscribe
Here’s my situation: Have an M1 MacBook Air, a Windows laptop, an LG B7 television. The Mac and Windows laptops have no issue outputting to my computer monitors using a USB C to HDMI cable, USB C to DisplayPort cable or in the case of the Windows laptop, HDMI to HDMI cable. The Windows machine works to the LG TV with an HDMI to HDMI cable. However, neither the Windows or MacBook laptops work with the USB C to HDMI cable to the LG.
They both detect an “LG TV” as an external monitor but the TV gets no signal. I’ve ordered a new cable but I have this one- it’s relatively new https://a.co/d/
The cable works with both laptops and my computer monitors so it’s not necessarily defective. Does this sound like a cable mismatch of some kind or some inherent issue with USB C to HDMI on the LG tv? I recall using an output from an older MacBook that had a USB 2 format to HDMI cable with the LG just fine several years ago. Any other ideas? Thanks!
They both detect an “LG TV” as an external monitor but the TV gets no signal. I’ve ordered a new cable but I have this one- it’s relatively new https://a.co/d/
The cable works with both laptops and my computer monitors so it’s not necessarily defective. Does this sound like a cable mismatch of some kind or some inherent issue with USB C to HDMI on the LG tv? I recall using an output from an older MacBook that had a USB 2 format to HDMI cable with the LG just fine several years ago. Any other ideas? Thanks!
First guess is that the HDMI copy protection handshake is not occurring with the newer USBC (hint is that the HDMI to HDMI is working fine)
Second guess is that the TV is not reporting its specs properly causing a resolution/refresh rate/edid error. Might be worth powering all systems off, connecting cable, and then powering laptop and TV in sequence to see if that detects properly.
Third guess is refresh rate is different than expected and display adapter is freaking out; try to set a different rate if possible upon connection?
Good luck.
posted by Khazk at 2:01 AM on December 26, 2023 [2 favorites]
Second guess is that the TV is not reporting its specs properly causing a resolution/refresh rate/edid error. Might be worth powering all systems off, connecting cable, and then powering laptop and TV in sequence to see if that detects properly.
Third guess is refresh rate is different than expected and display adapter is freaking out; try to set a different rate if possible upon connection?
Good luck.
posted by Khazk at 2:01 AM on December 26, 2023 [2 favorites]
Yeah, hdmi feels convenient but it's got a layer of aggressive encryption and copy protection built in and things just don't work sometimes when you try to convert signals. Kinda weird to think your TV is locking you out bc you're pirating content from your laptop right? So thank your local copyright hawk and intel for the gift of HDCP for breaking this reasonable use for you.
Anyway, it's not just as simple as getting the thing to plug in, you need to do some signal processing and add in a new HDCP handshake, or have an endpoint that doesn't check for it, both of which may be technically legally dodgy.
I can't get your link to work, but you may need to get a little powered converter box that can add in a handshake, and these often let you tinker with resolution ons and refresh rates to cover the other cases Khazk mentions above. If you search for HDCP features specifically you may have better luck.
posted by SaltySalticid at 5:21 AM on December 26, 2023 [1 favorite]
Anyway, it's not just as simple as getting the thing to plug in, you need to do some signal processing and add in a new HDCP handshake, or have an endpoint that doesn't check for it, both of which may be technically legally dodgy.
I can't get your link to work, but you may need to get a little powered converter box that can add in a handshake, and these often let you tinker with resolution ons and refresh rates to cover the other cases Khazk mentions above. If you search for HDCP features specifically you may have better luck.
posted by SaltySalticid at 5:21 AM on December 26, 2023 [1 favorite]
The tv is 4K. If the monitors are not or if the cable’s not properly rated for that (or is but has been damaged by bending too tight or various other things) it could be a problem where the usbc interface is negotiating a data rate higher than the cable can actually support but the other devices don’t. Or the usb hdmi interface just isn’t as good at making a signal and thinks it can do 4K but can’t really do it good enough
posted by aubilenon at 7:22 AM on December 26, 2023
posted by aubilenon at 7:22 AM on December 26, 2023
Response by poster: Clearing up a few things: the monitors are not 4k but the cable is rated for 4k. Here’s a working link: uni USB C to HDMI Cable for Home Office 6ft (4K@60Hz), USB Type C to HDMI Cable, Thunderbolt 4/3 Compatible with iPhone 15 Pro/Max, MacBook Pro/Air 2023, iPad Pro, Surface Book 2, Galaxy S23 https://a.co/d/5dsPAjY
Definitely checked the hdmi inputs on the tv, I’ve selected the correct one. I’ve also tried multiple hdmi inputs to rule out an issue with the inputs of the tv itself.
I’ve set refresh rate to 60hz, which it defaults to. Seems standard for 4k output over hdmi.
posted by arm426 at 7:27 AM on December 26, 2023
Definitely checked the hdmi inputs on the tv, I’ve selected the correct one. I’ve also tried multiple hdmi inputs to rule out an issue with the inputs of the tv itself.
I’ve set refresh rate to 60hz, which it defaults to. Seems standard for 4k output over hdmi.
posted by arm426 at 7:27 AM on December 26, 2023
On my laptop (an Asus) I can use a USB-C dock thingy to output HDMI, which works fine on my 2k TV, but doesn't work properly (corrupted picture) on my friend's 4k set. (On the same port I can use a USB-C to DisplayPort cable to plug it into my 4k 120 Hz monitor with no problem.)
4k over HDMI can be pretty wonky in general, in my experience.
posted by neckro23 at 12:56 PM on December 26, 2023
4k over HDMI can be pretty wonky in general, in my experience.
posted by neckro23 at 12:56 PM on December 26, 2023
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posted by phunniemee at 5:42 PM on December 25, 2023 [1 favorite]