Comment by mschuster91 | Hacker News Reader

Comment by mschuster91 | Hacker News Reader

> Several people eventually got involved, things were rebooted multiple times, cables were yanked and replugged in again. First after I installed arandr and forced-updated the resolution of my HDMI output to 1920×1080 the projector would suddenly show my presentation. (Later on I was told that people had the same problem in this room the day before…)

That's why it is a good idea if you're a presenter to always have a Decimator [1] or its cheaper and less-capable alternative from BMD [2] in your pocket. No matter what, both of them will make sure you can get at least a signal to any sink with an HDMI or SDI port. Even 20 years after EDID, negotiation issues reign supreme...

Personally, when I'm responsible for inhouse conferences, I always have the venue place a Decimator at the presenter desk and run the cable to the projector using SDI - particularly MacBooks and their USB-C dongles tend to have issues with cable lengths above 5-10 meters, I'd guess too low voltage swing.

I literally never ran into incompatibility issues with this setup, only issue I had was some dumbass thinking they could unplug the Decimator to charge their phone. Additionally, SDI makes it very easy to install a split-off run to a central recording site, even if it's 100 meters of cable run away, or a split screen at the presenter's feet. No negotiation issues, everything Just F...ing Works.

[1] https://decimator.com/Products/MiniConverters/12G-CROSS/12G-...

[2] https://www.blackmagicdesign.com/de/products/miniconverters/...

Interesting, what exactly does the Decimator do?

(Side note: I don't think it is a particularly clever idea of Decimator Design to fill their logo and homepage with images of large spiders. They are effectively eliminating around 10% of the population with arachnophobia as customers, and are making the experience of visiting their website slightly uncomfortable for large parts of the remaining population.)

> Interesting, what exactly does the Decimator do?

A multitude of things, depending on how you configure it:

- signal boosting of low-voltage or otherwise problematic HDMI or SDI signals, including reclocking. That's imposing virtually no latency and if you're running in a TV broadcast environment with centralized clocking it makes work easier for the downstream mixer. Primarily, it avoids issues with mis-designed sources such as cheap-ass adapter dongles that have signal integrity issues - as long as it's "good enough" for the Decimator to recognize it will output a clean and high-strength signal.

- format conversion from HDMI/DVI to SDI and vice versa. That imposes a tiny bit of latency and allows the usage of "consumer" equipment with broadcast equipment, or if you use two Decimators linked by SDI, you can "just" go for far longer cable runs than you could ever do with HDMI - up to 100m, in practice way more.

- up and downscaling as well as framerate conversions. This is where things really get interesting - no matter what kind of source and sink you use or what their limitations are, the scaler engine can make them talk. That includes color space conversions and bandwidth as well, and it's particularly useful if you, say, have a 12G SDI link from the source to the sink, and you want to use an older display for additional monitoring. Splice a Decimator in there and it will output the full quality signal on one output while providing a scaled-down signal on the second output.

Yeah, that’s the perfect case of a good product overrun by a questionable design idea. And its name sounds 13yo too, tbh.

Decimator Design excluding 10% of the population is a historically accurate decimation.

Yes, SDI was just designed for this kind of thing (moving video long distances between cameras in studios, tape decks and patch bays in technical rooms, vision switches and capture equipment in editing bays, etc.), whereas HDMI was only ever designed for connections of a few metres (and then active optical cables had to be made to try and fix the mess)…

I agree. I personally leave my Decimator MD-HX’s in ‘Free Run’ scaling mode at my preferred resolution. The in-built ‘no signal colour’ of my choosing helps me troubleshoot the problem in a signal chain quickly.

Worth mentioning for the novices that SDI does not do HDCP, so you can’t pass copy-protected content via this setup without workarounds.

Of course, it really should be up to the conference AV suppliers to organise all this, not the presenters themselves.

> Worth mentioning for the novices that SDI does not do HDCP, so you can’t pass copy-protected content via this setup without workarounds.

Well, the workaround is a 10$ HDCP stripper from ebay. Easy enough. (And I think that both Decimators and BMD converters also strip HDCP, but don't quote me on that)

> Of course, it really should be up to the conference AV suppliers to organise all this, not the presenters themselves.

Well, conference setups tend to be a hit and miss IME. Some where the venue and the conference is run by dedicated professionals, you don't even have to tell them to place Decimators and SDI cable runs, they'll come in with these from the start in their offer... but a lot of smaller venues and conferences (especially those ran by volunteers / NGOs) don't have that knowledge and just place some random home cinema projector together with a 20 meter HDMI cable. Corporate offices are just as bad IME, I've never seen a corp conference room with anything but HDMI or, in the worst cases, VGA. Corporate just doesn't give a flying fuck unless they got a dedicated team and a proper budget working on conference room setups...

It looks like the MD-HX is what you want for this use case?

I do a bunch of international travel, and the HD-LX seems ideal sized, but it seems like it doesn't do most of the useful functions?

It's "only" 3G-SDI so FullHD only.

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