Decklink Video Support

[thatcherfreeman]

Expected behavior of the wanted feature

Something that's completely absent from the market right now is a free, lightweight, open source application that can play video and send it (the colors straight out of the decode, without any further color processing applied besides a resize) to a Blackmagic Decklink or Ultrastudio for it to be played back on a reference monitor. Blackmagic provides an SDK that's reasonably easy to integrate with.

I would expect the resulting integration to have the following options:

1. Decklink Device selection
2. Resolution/framerate selection
3. Chroma subsampling (bit depth, 4:2:2 YUV, or RGB)
4. Legal or Full levels selection
5. SDI single/dual/quad link selection.
6. Checkbox to release control of the device if MPV loses focus.

Because MPV is open source and cross platform, I think it would be an excellent candidate for this feature. ffmpeg already has some decklink support though it requires different compilation flags when you build ffmpeg, so that might reduce the work needed to support this.

Personally, I think this would be useful for more than just video professionals. This would democratize the ability for A/V enthusiasts to send the same signal to their displays as what was used when movies were professionally mastered, bypassing any OS color management mishaps along the way. This limits the complexity of the image pipeline and ensures accurate reproduction of the image for anyone who has a calibrated monitor and a breakout box, which isn't particularly expensive.

Alternative behavior of the wanted feature

No response

Log File

No response

Sample Files

No response

[kasper93]

There are decklink in/out devices implementated in ffmpeg, you can use that. Not sure if it maps to mpv usecases cleanly, but I'm not interested in diving into whole ecosystem if I don't use it myself.

[thatcherfreeman]

My issue with just using ffmpeg is that generally these sorts of video users aren't technically competent enough to compile ffmpeg from source with different flags, whereas mpv is very easy to install and run. I think it's a bit of a shame that there isn't an existing solution that enables a video clean feed but is also easy to install and use.

Tbf the amount of work needed to add decklink support here might not be as bad as you think. There's a free (in the sense of monetary cost) SDK offered by blackmagic design, and something like Claude may be able to do most of the heavy lifting. I was able to get it to add decklink support to nomacs via a plugin yesterday.

I'm happy to buy you a decklink and compensate you if you'd build this feature. That would save me a lot of time getting the build environment set up for MPV and ultimately getting the PR checked in, which is the route I'll attempt if you're truly not interested.

[kasper93]

mpv itself is wrapping ffmpeg heavily. You should be able to use decklink device exposed by ffmpeg libraries from mpv itself. We don't have to implement SDK access directly.

Something like mpv "av://decklink:<devname>" would be a start, you might need to specify the video format directly, and other options through --demuxer-lavf-o=. I don't know exact way, because I don't even have this support compiled in.

My issue with just using ffmpeg is that generally these sorts of video users aren't technically competent enough to compile ffmpeg from source with different flags, whereas mpv is very easy to install and run.

Well, while mpv may be little easier to compile than ffmpeg, the end result is the same. You would need to compile mpv with specific flags, same as you need to compile ffmpeg with specific flags (SDK support). In both cases, it's likely not be enabled by default, because SDK like decklink one is not freely distributed, so you need to access it first to even start building it. Even if it is free, it is behind register wall.

[Andarwinux]

FYI, https://gitlab.com/m-ab-s/decklink-headers

As for Windows, it is incompatible with win32threads so I gave up on trying to add it to zhongfly's builds.