Wireless projection using Miracast technology

Miracast is now a standard feature in the mobile operating system Google Android and the Microsoft Windows desktop operating system. Newer televisions and more expensive projectors provide support for Miracast as a wireless display. If our display device does not support Miracast, we do not need to despair, as there are many small hardware devices (dongles/sticks) that can be connected to the HDMI port of a television/projector and enable Miracast connectivity (an example is the Microsoft Wireless Display Adapter).

An important feature of Miracast (compared to other technologies) is that the transmission is not through a computer network, but through a direct connection between the two devices. This eliminates a number of delays and complications. We cannot project over long distances, but the goal of this technology is to project onto a display that we are simultaneously looking at.

There are many practical uses. We can connect a monitor/TV to a computer without using cables. We can show our friends photos from our vacation on a TV directly from our mobile device. We can present on a projector from a tablet or phone. We can demonstrate a mobile application using a projector on a surface or in a Windows environment.

About Miracast Technology

Miracast is a standardized solution from the WiFi Alliance for wireless transmission of audio and video. Miracast is a certification program according to the Wi-Fi Alliance Wi-Fi Display specification. It allows wireless connection of devices (such as a phone, laptop, or tablet) to a display (such as a TV, monitor, or projector). It is often referred to as Wireless Display and the term Screen Mirroring is used. It may also be referred to as HDMI over WiFi, as it replaces the HDMI cable.

Other Solutions - DLNA, WiDi, AirPlay

Wireless video transmission has been a popular idea for many years. Various manufacturers have tried to promote their own solutions. Probably the most widespread was DLNA (Digital Living Network Alliance), created by a group of hardware manufacturers (led by Sony), which is still evolving. But I would say that Miracast is now pushing all others aside and is the majority used solution. Only Apple sticks to its AirPlay and does not support Miracast.

Intel tried to create its own technology Intel WiDi (Wireless Display) and Intel Pro WiDi (with features for businesses), which was compatible with the Miracast protocol. But since Miracast has spread so much, it has discontinued its initiative. The official notice is Intel® WiDi and Intel® Pro WiDi Applications Have Been Discontinued.

Native Support in Operating Systems

Microsoft added native support for wireless display projection using Miracast (Project to a wireless display with Miracast) already in Windows 8.1 and in Windows 10 (Anniversary Update 1607) also added the ability to function as a wireless display. In general, it uses the term Wireless Display.

Likewise, Google natively supports Miracast in its Android from version Android 4.4. It generally uses the term Screen Mirroring.

The image quality depends on the performance of the hardware and drivers. Initially, some devices could not project in FullHD, but current devices should not have any problems.

Documentation

Official information can be found on the Wi-Fi CERTIFIED Miracast page, the related technology Wi-Fi Direct is important. There is also a list of certified devices Miracast-certified products.

Used Technologies and Codecs

WiFi Direct

Miracast uses the WiFi Direct standard, which allows direct wireless connection between two devices (peer-to-peer). So there is no need for a WiFi network, routers or internet access. It also means greater security, as the data does not pass through a regular network. The connection also uses WPA2 encryption. To protect the content, Miracast supports HDCP 2.x (High-bandwidth Digital Content Protection).

Some WiFi Direct devices allow simultaneous connection to multiple networks, i.e. to the infrastructure (internet access) and peer-to-peer connection with the display (WiFi Direct). Currently, this seems to be a fairly common feature, both on phones and laptops, so we can use the wireless network to connect the display and still remain connected to the data network.

Audio and Video Codecs

Inside the WiFi Direct connection, Miracast uses a vendor-neutral wrapper, where they negotiate the video capabilities, set the content protection (if needed), stream the content and maintain the video session.

Miracast supports the ITU-T H.264 video codec (also known as Advanced Video Coding - AVC), Constrained Baseline Profile (CBP), Constrained High Profile (CHP) for high-resolution video. For audio, it supports a number of Linear Pulse-Code Modulation (LPCM), Advanced Audio Coding (AAC) and Dolby Advanced Codec 3 (AC3) modes. This allows streaming video up to 1920x1080px resolution and 5.1 surround sound. The protocol was designed for playing DVD content.

Required Support on the Client

On the client, we need support in the operating system (or a special application), further support on the wireless network card and support in the driver (graphics and WiFi card). In the case of computers with Windows 10, this support is common.

The wireless network card must support WiFi Direct (and optionally simultaneous connection to multiple networks, which Microsoft calls Virtual WiFi). It must have a corresponding driver that meets at least the NDIS 6.3 (Network Driver Interface Specification) specification. We can list the NDIS driver versions in PowerShell:

Get-NetAdapter | Select Name, NdisVersion

For the graphics card, we must have a driver with support for Wireless Display (Miracast), which is at least WDDM 1.3 (Windows Display Driver Model), which is designed for Windows 8.1.

Wireless Projection

From Microsoft Windows 10

In Windows, the wireless display behaves like a standard second screen (i.e., the same as if we connected a projector with a cable), so we can use the functions of mirroring, extending the display or projecting only to the second display. Microsoft uses the term Wireless Display.

In Windows 10, the use is very simple and intuitive:

• we must have WiFi turned on
• we press the Windows key and P or click on the Action Center icon in the bottom right corner and choose Project, or go straight to Connect (this skips the next step)
• under the projection mode, we click on the last option Connect to a wireless display
• the search for available devices will start, if we are within range of a turned on projector, it should appear in the list

• we click on the device and the connection process will start, sometimes it goes quickly, sometimes it takes up to 30 seconds (exceptionally, it may report an error, but by repeating it always connected correctly for me)

• after the connection, we can also check the option Allow input from a keyboard or mouse connected to this display, which will allow passing commands from the display to the computer, we can use this, for example, on projectors when controlling the projection with gestures
• to disconnect, we click on Disconnect

From Google Android

On Android devices, a lot depends on the Android version and any manufacturer customization. It should be found somewhere in the settings and the item name may vary. On the Samsung Galaxy S5 it is Settings - Connections - Screen Mirroring.

On the Sony Z5 Compact it is Settings - Device connection - Screen mirroring.

Using Windows 10 as a Wireless Display

The Anniversary Update 1607 for Windows 10 brought a new feature in the area of Miracast technology support. A computer with Windows no longer has to be just the source of projection to a wireless display, but it can itself become a wireless display for other devices. This can be useful, for example, when we don't have a Miracast-enabled projector and want to project content from an Android mobile device.

The use is again very simple (we must have functional Miracast support):

• we must have WiFi turned on
• we press the Windows key and P or click on the Action Center icon in the bottom right corner and choose Project, or go straight to Connect (this skips the next step)
• at the bottom, we choose Projecting to this PC, which will take us to the display settings (we can also access this via PC Settings - System - Projecting to this PC)

• in the settings, in the first combo box we allow connecting to the computer by setting Available everywhere

• in the second combo box, we choose whether we need to allow projection each time it connects or only the first time, when the device connects, the following dialog will be displayed

• the Require PIN for pairing switch can require entering a PIN (which is displayed on the PC and must be entered on the device) for pairing to occur (requiring a PIN may cause problems)
• the last switch allows projection only when the computer is connected to a power source