unixgreybeard wrote: ↑Sat Dec 28, 2024 12:20 am
I wonder how many people buy them without realizing.
I would suspect people do get caught out. A similar pitfall occurred on the transition from PS/2 (4 pin minidin) mice/keyboard to USB mice/keyboards. The two interfaces are totally different, at first glance. However ...
Some of the newer USB mice had a "compability mode" where they were able to, with the correct _dumb adapter_ be used as a PS/2 mouse on an older system. The adapter was literally a USB and 4-pin minidin, wired to pass +5v and 0v on the right pins, and the "clock and data" wires of PS/2 into the "data+ and data-" of USB. The adapters were nothing of any use APART from the physical connector change. All the smarts was in the mouse.
This doesn't stop people selling that very adapter as "USB to PS/2" converter. Which it is. Kinda. But it won't help you at all if you have a PS/2 mouse (which knew nothing about USB) or a USB mouse that was just a no-frills-USB-only mouse that couldn't go into emulation mode. "Hmmm, I'm connected to something, it won't talk USB on the differential pair, let's try talking PS/2 serial instead? Ah hello!"
I've got a Line-6 POD guitar effects unit. It's got an RJ45 8P8C "network" connector on the back. You can guess from the context that it would not be expecting to be plugged into my network, it has no clue about networking. That's for connecting an external footboard for switches/LEDs/Wah-pedal ... they just used a convenient connector with no implied meaning beyond that. 48v Power-Over-Ethernet up _that_ wouldn't be fun.
unixgreybeard wrote: ↑Sat Dec 28, 2024 12:20 am
... can ZoneMinder use an HD-TVI feed from the cameras directly?
Taking the question literally, no.
Zoneminder is software, it can't do anything without a) the right hardware and b) kernel/driver support.
So, if you have a reasonably standards compliant IP-Camera (JPG, MJPG, x264/265 etc.) then hardware is "your existing network card" and kernel/driver is "comes with Linux!"
If you have an analogue PAL/NTSC SD camera setup then the hardware is e.g. BT848 PCI cards (BNC/Phono/Composite/SVideo) and software is BTTV driver, which presents it as /dev/video. Similar for USB analogue capture dongles, although these are external not internal.
Higher resolution analogue, so-called "HD" analogue would need better (faster) chips than the BT848 series, which are SD only.
I don't know about HDMI capturing, I've never needed to do that, but solutions must exist as people use various methods to get HDMI out from cameras etc. into OBSstudio for streaming/YouTubing on Linux.
If you can get the camera's actual hardware output, in whatever format, into an IP stream _or_ into a Linux supported capture hardware, then you should be able to get Zoneminder to do the next step of the job.
unixgreybeard wrote: ↑Sat Dec 28, 2024 12:20 am
.... but nailing the specs down might be an issue. Do the sellers even know how they present ...
A good chance they don't know. The presence of a network port is a good sign. But it doesn't guarantee anything, e.g. "no that's only there to access a web configurator, or to access files that have BEEN recorded by the DVR internally. Live streams? Dunno..." so you need to search. Either search for that model number + other people's projects using/abusing the DVR as a capture device. Or, try and find the manual online and have a good read through it. Many items I've considered buying have been squashed at that stage, because it doesn't do something important!!
If there's no model number, and the seller has no idea, then you are on your own on that one. Also, returning it because "It does work, but doesn't do what I wanted, although you never confirmed it would!" isn't going to be easy ...