Reply 200 of 263, by christal87
doshea wrote on 2021-12-26, 05:11:christal87 wrote on 2021-07-27, 18:48:
Note on some "el cheapo" webcam based USB video class (UVC) HDMI capture devices: [...] most of these dongles want to look like USB3, but most are only 2.0 High Speed (HS). This means that uncompressed raw video (e.g. YUYV) will have a limitation either on framerate or maximum resolution, whichever you choose (game capture at 5FPS is not great). You simply can't dunk down like 2.1+MPixels (1920x1080@30...60Hz uncompressed on USB2. It's worth looking for true USB3 capture dongles in the future to avoid this huge limitation.
I also bought a "TenYua" brand "USB 3.0 HDMI Video Grabber" from Amazon - https://www.amazon.com.au/gp/product/B089YMY71Y - since I understood that I needed USB 3 to get good frame rates, but it turned out that it could only capture 640x480 YUYV at 30 FPS, and higher resolutions were much lower frame rates like 5 FPS. On checking lsusb -v in Linux I can see it's really only USB 2.0. I suppose I could probably get my money back on this one too but I'm not sure if I could find a better one that doesn't cost a lot more. Perhaps I could have found a cheaper one that works just as well but doesn't pretend to be USB 3?
Are there any hints that a device isn't really USB 3? This particular device requires a USB A to A cable. I've never seen a USB device/gadget with a USB A socket before, this seems strange to me. I wonder if a blue USB A port is just the cheapest way to make your device look like it's USB 3 when it's not really?
Merry Christmas everyone,
Nice to see a fellow linux user. 😀 I've checked the amazon link you have shared. There seems to be no real telltale sign of it not being USB3 if you only look at the title. Because these el cheapo adapters are a pig in a poke, you have to always have some kind of suspicion before buying. If you look carefully the title says USB3, but the third illustration loops HDMI signal through it from a PC to a TV set and states that the third (recording) machine (wich is a notebook) is connected with "USB2.0 output".
Seems to me like Amazon can't really write a good enough product description because the chinese spec was already dubious. There's also a language barrier there and most chinese product manuals are well known for unusable eng/ger/fra/etc translations. I'm hungarian and we're left out of the rain almost every time, but I can tell by the english manuals. At a time there was a domestic meme about a cheap 27MHz wireless keyboard, which the chinese translated directly into hungarian as "wireless telegraph keyboard" (arc telegraph literally in hungarian). I've never seen direct chinese-hungarian translations ever since. 😀 A few years ago I fell for a non-isolated MBUS adapter PCB on aliexpress the same way: title stated it's isolated but the pictures and pricing quickly revealed no isolation whatsoever.
Before you get a refund on this you can try a workaround for the 5FPS limit by a query to it's Video for Linux 2 (V4L2) API representation with v4l2-ctl. Most of these are only a simple USB cam SoC and an HDMI transceiver hanging on the SoCs image sensor input, integrated together. So you may have some registers exposed which configure video format, etc like a webcam would. YUYV is uncompressed and more desirable, but USB2.0 quickly reaches a bandwidth limitation with it. You can try switching to MJPEG to have an adequately high FPS (even 60FPS on lower resolutions is some cases). On the other hand you may not like the compression artefacts, but I had the same issues with my cheap ass USB2.0 grabber and switching to MJPEG was not bad at all. I haven't really noticed degradation. The next thing you can do is tweak the default color setings. USB-A to A plugs aren't standard because you could plug two USB host ports together. Later if it gets broken you may have a hard time replacing the cable, but a lot of chinese stuff do this to cut down costs. I've bought a flash drive style donge which is bulky, so I've added a 30cm (10") long USB extender "pigtail". Try to look for the blue color connector and the Superspeed (SS) logo too. Also the price is at least double of the USB2.0 one.
Example product (which looks good but according to reviews don't expect 4K features to work) : https://www.amazon.com.au/Capture-Recording-A … s/dp/B082XCH1SV