How to stream 4K video using VDO.Ninja

Sending a 4K video feed with VDO.Ninja is very CPU intensive. Be prepared to use all of 8 real cpu cores (not threads).

How VDO.Ninja handles video quality

VDO.Ninja has 3 predefined &quality levels:

• &quality=0 tries to do 1080p (1920x1080 @ 60fps).

• &quality=1 is the default. It tries to select 720p (1280x720 @ 30fps ) for both screen capture and webcam.

• &quality=2 tries to do 360p (640x360 @ 30 fps).

• also there's &quality=-1 , which will use the device's default resolution, but this could be anything, low or high, so it's a niche option.

By “trying”, I mean that if the resolution is not available, VDO.Ninja defaults to another resolution that the camera supports instead. This way, no errors are thrown and a compatible stream is sent, even if it’s not exactly what you might have desired.

VDO.Ninja is however capable of doing higher resolutions and custom resolutions however; you just need to manually specify the resolution you want. When you manually specify a resolution, if it doesn’t work, an error is thrown.

While I could make a selectable option for 4K in the user interface, another problem with 4K is that it requires a LOT of CPU power to encode. Most users will always select the highest resolution allowed, not understanding that it might actually be a bad idea. Maxing out your CPU can actually result in worse quality with lower frame rates than selecting a lower, safer, resolution.

Pushing 4K resolution

4k comparison chart with lesser resolutions

That all said, you can give “4K” a go by adding &width=3840&height=2160 to the invite link.

For example then, https://vdo.ninja/?push=inviteGuest123&width=3840&height=2160

If the guest does not support 4K, this will give an error to the guest, stating that the video device is over-constrained.

The default frame rate is 60-fps, although if their device does not support that, it will use a lower support frame rate. If you manually specify a frame rate, and the camera or display does not support it, it will also give an error.

Smartphones

If streaming from a smartphone, not all phones can do 4K; my old LG V30 I believe could do 4K30 via VDO.Ninja, but my Pixel 4a seems stuck at 1080p30. As well, an iPhone 11 might only be able to 1080p30, an iPhone 12 might be able to do 1080p60, while an iPhone 15 might be able to do 4K30. It might depend on the iOS version, where older iOS versions are pretty limited, so things will change overtime.

A common question I also get is that a certain phone can record 4K60 in the native phone app, so why not also in VDO.Ninja? Well, just because you can record to disk at 4K does not mean the manufacture has added support for 4K streaming via the browser. It requires additional development, nor is it always possible if the hardware encoder used does not support the advanced requirements of WebRTC.

Samsung devices can sometimes use the built in Samsung Internet browser instead of Chrome to get access to higher resolutions and frame rates; 1080p60 for example with new flagship devices. Sometimes changing cameras or video codecs can allow for higher resolutions as well.

The native mobile app version of VDO.Ninja may at some point support additional cameras that the browser does not, but at present there are not enough development resources available for this. It's desired however.

What about the bitrate?

Next, while you might have selected 4K, with the exception of static video screen shares, you cannot transfer 4K video with the default video bitrates set. For action, you will need closer to 40-mbps video bitrates set on the viewer’s end. For talking head videos, you will want over 10-mbps and possibly even more. Without a high enough bitrate set, the video will not stream at 4K and more than likely not maintain 60-fps.

To set a target bitrate add &videobitrate=20000 for 20-mbps for example. This goes on the viewer link.

Scaling

You may need to add &scale=100 to the view link to have the video stream at 4K, if the playback window is smaller than 4K. VDO.Ninja by default resizes incoming videos to fit the playback area, and &scale=100 overrides that, requesting 100% of the available resolution; so unscaled if possible.

Codec

A bit like bitrate and scaling, changing the video codec can sometimes help with achieving 4K video. &codec=av1 can help if the bandwidth is limited, as it is more efficient than other codecs. &codec=vp8 is universal, while &codec=h264 can often trigger the hardware encoder to be used. Using a hardware encoder can help reduce CPU load, allowing for 4K if the system would otherwise be CPU-bottlenecked.

Normally you shouldn't need to change codecs, but sometimes it does make a difference.

Performance issues

As a result, to successfully stream 4K video, you generally need a computer system with 8 real CPU cores or more, running at 3.6ghz or higher. A modern AMD 3900X-series CPU or Intel 9900K CPU are ideal for this task, but a quad-core laptop will not be. You might be able to get away with lesser bitrates and lesser CPU requirements if just screen-sharing text, but it still is not for the faint of heart.

Lastly, MacOS users may find that 4K is simply not possible or very difficult. If you do manage to get it working, it might only operate at 5-fps or so. I don’t quite know why this is, but if you intend on sharing 4K video, you might be better off using a Windows PC. It seems to perform better.

We've successfully streamed 4K50 over 5G cellular Internet at 65-mbps using a MacBook Air M1 and VDO.Ninja.