Apple TV airplay slow streaming from macbook pro

Hi Nemooo. There's a big difference between AirPlay mirroring and basic AirPlay. Please read the following:

Video AirPlay works in two modes. Basic AirPlay just sends the video URL to Apple TV, which then streams it directly. This usually works best since there's no double transmission. You're using basic AirPlay when the video player on your device goes black and says "This video is playing on Apple TV". On a computer, you enable this using the AirPlay icon that appears in the controls of a screen video player object, inside the browser or other app. On iPad or iPhone, use the AirPlay controls on the right hand pane of the iOS 10 Control Center (on iPhone, tap the arrow with circles icon at the bottom), or the AirPlay icon in the video player. An app can prevent basic AirPlay, and a website may have requirements that only work in the browser, so basic AirPlay may not always work.

The other mode is Mirroring, which generates an H.264 video stream from the device frame buffer and transmits it over WiFi to Apple TV. This video compression inherently limits resolution, and may have trouble with fast motion. On iPad or iPhone, mirroring is on the left hand pane of the iOS 10 Control Center. On a Mac computer, you access this mode from the AirPlay icon in the main menu bar. It lets you mirror the main display, or create a new display, extending the desktop. But remember that the data sent to the Apple TV is always being converted to a live video stream. Unlike a normal wired monitor connection, actual display frame buffer pixels are not transmitted. When you put the iPad or iPhone video player into full screen mode, mirroring may automatically switch to basic AirPlay. If the server doesn't support basic AirPlay, this may prevent mirroring full screen video.

I don't believe you can activate basic AirPlay globally in Mac OS. It needs to be offered by the player, in the form of an icon in its controls (rectangle sitting on up-arrow). It should be available in QuickTime. If it's not in VLC, and you have Apple TV 4, you can install the tvOS VLC app, and access your videos from Apple TV. As I said, basic AirPlay is much better than mirroring, since it streams the video direct to Apple TV, instead of manufacturing a new video stream on the fly.

Please reread my description of mirroring. It uses the graphics processor in your computer to convert the frame buffer to a video stream on the fly. That requires significant data processing power, since it's not just about putting the bits in the correct order. What generation is your MacBook Pro?

Mirroring is only available on hardware that Apple deems capable of supporting it, therefore if you encounter problems with delayed or stuttering transmission you either have a problem with your Mac in general or most commonly a problem on your network.

As mirroring is essentially live and basic airplay isn't mirroring can cause a problem with a poor network where basic airplay or home sharing doesn't, however out of interest what sort of performance do you get from home sharing, if you get problems there then it's most likely a network issue, but no problem doesn't necessarily rule out a networking issue though.

does it work well if you connect both by ethernet to the router ?

if so then it's likely network interference which cause data packet retransmits a lot and hurt the performance