this post was submitted on 09 Sep 2024
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[–] xep@fedia.io 76 points 2 months ago (1 children)

Yes, this is incredibly annoying and it's also the reason why some USB cables cost more than others, even they may look the same superficially.

[–] FierySpectre@lemmy.world 25 points 2 months ago (2 children)

One of those cables that don't work is rated for like 120W, with gigabit transfer speed... But it refuses to transmit display.... Like bruh

[–] TonyTonyChopper@mander.xyz 32 points 2 months ago (2 children)

1080p at 60 Hz is 4.4 gigabit

[–] FierySpectre@lemmy.world 19 points 2 months ago* (last edited 2 months ago)

Didn't really think about that one but you're right damn... (Looked it up, and it depends on the bit depth etc, but it's around 3.2Gbps for the display settings if I'm correct)... So that explains a lot

Gigabit is capable of like 720p@30Hz which it probably should be able to fall back on, but I understand why they wouldn't do that haha. 1080p@15Hz is also possible :)

[–] zarenki@lemmy.ml 7 points 2 months ago

USB-C video is usually DisplayPort Alt Mode, which uses a completely different data rate and protocol from USB.

Even using old 2016 hardware, a computer and USB-C cable that both only support 5 Gbps USB (such as USB 3.1 Gen 1) can often easily transmit an uncompressed 4K 60Hz video stream over that cable, using about 15.7Gbps of DisplayPort 1.2 bandwidth. Could go far higher than that with DP 2.0.

Some less common video-over-USB devices/docks use DisplayLink instead, which is indeed contained within USB packets and bound by the USB data rate, but it uses lossy compression so those uncompressed numbers aren't directly comparable.

[–] tobogganablaze@lemmus.org 4 points 2 months ago (1 children)

That sounds like a dedicated charging cable. So yeah, they will (if at all) only transfer data slowly and not support any extras features like displayport.

[–] damniticant@lemmy.world 4 points 2 months ago (1 children)

A dedicated charging cable wouldn’t have “gigabit speed”

[–] tobogganablaze@lemmus.org 1 points 2 months ago* (last edited 2 months ago) (1 children)

No USB cable has “gigabit speed”. It probably has 480 Mbps (USB 2.0 standard).

Maybe he meant a 5 Gbps Gen1 cable. That would be “gigabit speed” but still rather slow by today's standards and won't support DP. They are pretty cheap these days, so wouldn't be suprising to see left over stocks being sold as charging cables.

[–] tal@lemmy.today 3 points 2 months ago (1 children)

No USB cable has “gigabit speed”. It probably has 480 Mbps (USB 2.0 standard).

What? I'm either misunderstanding you or this statement isn't correct. Having USB cables that can move data at gigabit rates has been common for quite some years.

Here's the latest stuff:

https://en.wikipedia.org/wiki/USB4

Bitrate

20 Gbit/s
40 Gbit/s
80 Gbit/s
120/40 Gbit/s asymmetric

[–] tobogganablaze@lemmus.org 2 points 2 months ago (1 children)

What? I’m either misunderstanding you or this statement isn’t correct

I meant that no USB standard actually has exactly 1 Gbit/s. I even mention that next one if 5Gbit/s. Just a misunderstanding I think.

[–] tal@lemmy.today 1 points 2 months ago

Oh, okay, makes sense, thanks.