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Some basic info about USB
(lemmy.world)
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this post was submitted on 09 Sep 2024
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It gets even better, each function of the port also needs proper support from the cable. Often cables do not support the full spec of usb to cut costs.
While the symbols in the post are often put on computers, for usb cables this is seldom done (only a few brands do).
Source: had to find a cable that supports both DP and PD to connect a portable external monitor after I lost the original cable. (1/9 cables worked)
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.
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
1080p at 60 Hz is 4.4 gigabit
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 :)
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.