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Comment by formerly_proven | Hacker News Reader

In the film editing space workstations use dedicated video I/O hardware which fully circumvents the display/video stack of the OS to be able to input/output exactly the pixels you want in exactly the format you want (something that's essentially impossible using OS facilities, much less in a cross-platform manner). This seems like a very good application for those cards (they're not particularly expensive, around 200 bucks [1]).

[1] https://www.blackmagicdesign.com/products/decklink/techspecs... (4K, PCIe) https://www.blackmagicdesign.com/products/ultrastudio/techsp... (less than 100 bucks, but only 1080p on Thunderbolt) (SDK: https://www.blackmagicdesign.com/developer/product/capture-a...)

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I'm 100% certain that most professionals are already using these for performance displays. I don't know a single person that doesn't use these cards for exactly this reason. We even use one for presentations/events at movie theatres just to make sure that nothing is going to put an errant pop up on the display.

How do you operate them? Do they show up as another graphics card?

No. If they did, that would defeat the purpose. Usually, they have their own setup software or routing software. Something like Blackmagic, for example, is supported directly from certain apps. Others let you route windows to the output. You still need a graphics card for these to work. They only handle the video input and output.

Ok. I'm on Linux and want to play a movie with VLC through this thing. Do I need the Blackmagic app to act as a bridge or something?

I'm not terribly familiar with Linux use of hardware I/O devices so my guess would be yes unless Blackmagic (or someone else) makes some kind of Linux kernel extension that would allow you to manually specify that or VLC has built-in support for external I/O devices.

Edit: Just checked because I was curious. The default installs of VLC do not include Blackmagic support but you can compile versions from the source for Linux that include it (if you also download the support files from Blacklink first).

Not sure about VLC, but ffmpeg has great support for Blackmagic, you just have to download the Blackmagic SDK, compile ffmpeg with Blackmagic support (and the SDK in path) and then you'll have a separate input/output device available in ffmpeg. The other great thing about this approach is that this way audio also takes a dedicated, integrated path, bypassing OS layers and maintaining sync with much less effort.

VLC has built-in support for Blackmagic SDI output cards:

https://github.com/videolan/vlc/blob/master/modules/video_ou...

Though a quick search through online forums suggest that module isn't compiled into Ubuntu's version of VLC by default, so you may need to compile your own version:

https://gist.github.com/afriza/cd9ce01a7b47b9bd3f192e95af1a0...

I can confirm. This is what I was able to find too. You can compile from source using the support files from Blackmagic.

Are they capable of realtime GPU-rendered graphics out of the box, or just video?

You can render on your GPU to a texture, then stream that texture to these devices. No different to rendering to your screen and then streaming and saving to disk, as you would do if you were screen capturing.

They need a GPU to function. They are just input/output devices.

A good suggestion if you have the budget. NDI is also incredible for this. But small producers rely heavily on built-in I/O on their computers, and I suspect that the market share from small/amateur streamers using Apple products outsizes Apple’s revenue from large shops today.

Big productions can afford Decklinks and media servers like Disguise D3.

Small producers spend lots of money on equipment in that range of cost, even for ancillary things like lighting and cables. I think it's a great recommendation.

There are a lot of guys out there with 2016 era macbooks (cause it still has HDMI) running it into a projector to do visuals at small clubs and things like that.

Maybe some of those guys scraped together enough money to buy one of the new macbooks (since it got HDMI back). Being forced to spend another $200 to get rid of a stupid orange dot would really sting.

2015 was the last MacBook with HDMI. Anyways I agree with you but it's true there is a lot of the richer professionals too - those who buy the new maxxed out MacBooks.

Incredibly, the new Macbook Pros released this year have HDMI, a SD card slot, and MagSafe.

Those guys can probably crop at the projector though and not lose too much? Last I played with projectors was around 2010 and back then crop controls already came standard

They surely have enough money to buy macbooks, and something like this is a fraction of the cost (seems about 10%).

Of course, I'm also confident that software workarounds will exist in the meantime.

NDI is fantastic, having dealt with racks of gear for switching and video distribution before I get excited about the possibilities every time I play with it. Dedicated hardware for bridging NDI to input and output devices is also appearing. It's a lossy solution (the video is compressed, unlike SDI/HDMI) but for live productions I'd definitely be willing to use NDI throughout (cameras -> switching -> recording/projection/streaming).

So long as they keep NDI Tools free. It would be great if they could also eventually build in some of the functionality of Dante (NDI is something like Dante but for video) since the Dante software toolkit is very much not free. I think Newtek has been on the right track.

Birddog has a great selection of dedicated NDI hardware that we found to be rock solid.

Indeed, we use three of the Flex 4K Out boxes to three projectors doing alpha blending to form a single virtual screen via ProPresenter and it works great!

Especially since someone donated an M1 Mac Mini, not realizing it only supported two traditional external monitors. With NDI we could have an external monitor for the operator display then let ProPresenter generate three virtual monitors via NDI. We can send differently formatted "screens" via NDI to our OBS computer for streaming too - different configurations of lower thirds for texts, full screen mirroring of the main presentation display - whatever we need. NDI really works a treat and I will NEVER go back to analog video again!

We also use the Birddog NDI PTZ cameras for streaming and some crude IMAG too - it's amazing how well NDI works.

What is this equipment called? It sounds like the opposite of a capture card.

edit: looking at your updated post, it is called a "playback card."

Yep. Used heavily for editing works, colour grading works for tv / film, sound works. Pretty much anything professional, they will discard what the GPU is doing (and inbuilt audio) and use these sorts of external devices.

This way, you know EXACTLY what the program is computing, nothing else.

Could you give an example of such a card? (model/name)

Also what’s the use case where they can’t export the video and transfer it as a file or byte stream?

These are great: https://www.blackmagicdesign.com/products/ultrastudio/techsp...

Use case: live (minimizing latency), no compression, compatibility with other gear.

https://www.blackmagicdesign.com/developer/product/capture-a...

The cheapness of greenscreen effects makes it pretty cheap to use in TV shows a lot these days though.

Booting Linux and displaying some graphics on DRM-KMS sounds much saner.

I'm guessing the downvotes are because your suggestion seems like a pretty big departure from these users' existing setups.

I think the migration costs (including the learning curves) might seem like a poor tradeoff.

And the fact that linux on new Macbook Pros isn’t feature complete yet.

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