[Windows][macOS] 8K video playback low performance

[itlancer]

Problem Description

8K video playback extremely laggy with low performance with Windows/macOS devices.

It has been tested with multiple AIR versions, even with latest AIR 50.0.0.1 with multiple Windows/macOS devices with different AIR applications with different videos. Tried with with Video, StageVideo and VideoTexture.
Same problem in all cases with all devices (even high-end).
Some devices:

• Windows 10 Pro 64-bit, AMD Ryzen 5 3600 6-Core Processor (12 CPUs), ~3.6GHz, 32 GB RAM, AMD Radeon RX 580
• Windows 10 64-bit, Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz (8 cores), 64 GB RAM, AMD Radeon Pro 5500M
• macOS Big Sur 11.6.8, Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz (8 cores), 64 GB RAM, AMD Radeon Pro 5500M
• macOS Big Sur 11.6, Apple M1, 8 GB RAM

The same videos with different (non-AIR) video players or applications playback without lags. Even with system default video players.

Adding

<windows>
	<maxD3D>9</maxD3D>
</windows>

to application manifest didn't help.

With Linux video playback doesn't work at all: #1984

Related issues (not the same):
#2159
#646
#196
#85

Steps to Reproduce

Launch code below. It start video playback in a loop.
Note: tested with 64-bit version.
Application example with sources and example of video attached.
video_8k_performance.zip

package {
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.net.NetConnection;
	import flash.net.NetStream;
	import flash.media.Video;
	import flash.events.NetStatusEvent;
	
	public class Video8KPerformance extends Sprite {
		private var nc:NetConnection;
		private var ns:NetStream;
		private var video:Video = new Video(640, 480);
		
		public function Video8KPerformance() {
			addEventListener(Event.ADDED_TO_STAGE, init);
		}
		
		private function init(e:Event):void {
			removeEventListener(Event.ADDED_TO_STAGE, init);
			
			addChild(video);
			
			nc = new NetConnection();
			nc.addEventListener(NetStatusEvent.NET_STATUS, ncHandler);
			nc.connect(null);
		}
		
		private function ncHandler(e:NetStatusEvent):void {
			if (e.info.code == "NetConnection.Connect.Success"){
				ns = new NetStream(nc);
				ns.client = {onMetaData:getMeta};
				ns.addEventListener(NetStatusEvent.NET_STATUS, nsHandler);
				video.attachNetStream(ns);
				ns.play("8K.mp4");
			}
		}

		private function nsHandler(e:NetStatusEvent):void {
			trace(e.info.code);
			if (e.info.code == "NetStream.Play.Stop"){
				ns.play("8K.mp4");
			}
		}

		private function getMeta(mdata:Object):void {
			trace("meta", mdata.width);
			trace("height", mdata.height);
			trace("avcprofile", mdata.avcprofile);
			trace("videocodecid", mdata.videocodecid);
		}
	}
}

Actual Result:
Video playback extremely laggy with low performance.

Expected Result:
Video playback without performance issues.

Known Workarounds

none
*write your own native extension to playback video

[itlancer]

@ajwfrost
Just for info. Such MP4 H.264 files (7560*3840 resolution or bigger) doesn't play at all using new multimedia APIs (FileSource and Pipeline): #2503 (comment)
Tested with AIR 51.0.0.2 using 64-bit builds and Windows 10 x64.