Miracast


Miracast is a wireless communications standard created by the Wi-Fi Alliance which is designed to transmit video and sound from devices to display receivers. It uses Wi-Fi Direct to create an ad hoc encrypted wireless connection and can roughly be described as "HDMI over Wi-Fi", replacing cables in favor of wireless. Miracast is utilised in many devices and is used or branded under various names by different manufacturers, including Smart View, SmartShare, screen mirroring, Cast and Connect, wireless display and screen casting.
A related enterprise protocol named Miracast over Infrastructure functions using a central local area network instead, and is supported in Microsoft Windows.

Development

The Wi-Fi Alliance launched the Miracast certification program at the end of 2012. Devices that are Miracast-certified can communicate with each other, regardless of manufacturer. Nvidia announced support in 2012 for their Tegra 3 platform, and Freescale Semiconductor, Texas Instruments, Qualcomm, Marvell Technology Group and other chip vendors have also announced their plans to support the Miracast standard.
The Wi-Fi Alliance maintains a list of certified device models, which numbered over 13,200 as of 2024

Technical details

Miracast is based on the peer-to-peer Wi-Fi Direct standard. It allows sending up to 1080p HD video and 5.1 surround sound. The connection is created via WPS and therefore is secured with WPA2. IPv4 is used on the Internet layer. On the transport layer, TCP or UDP are used. On the application layer, the stream is initiated and controlled via RTSP, RTP for the data transfer.

Version history

Functionality

The technology was promoted to work across devices, regardless of brand. Miracast devices negotiate settings for each connection, which simplifies the process for the users. In particular, it obviates having to worry about format or codec details. Miracast is "effectively a wireless HDMI cable, copying everything from one screen to another using the H.264 codec and its own digital rights management layer emulating the HDMI system". The Wi-Fi Alliance suggested that Miracast could also be used by a set-top box wanting to stream content to a TV or tablet.
Both devices need to be Miracast certified for the technology to work. However, to stream music and movies to a non-certified device, Miracast adapters are available that plug into HDMI or USB ports. Certification does not mandate a maximum latency. Even with certification, it is possible an underpowered device will be constrained in performance or bandwidth.

Types of media streamed

Miracast can stream videos that are in 1080p, media with DRM such as DVDs, as well as protected premium content streaming, enabling devices to stream feature films and other copy-protected materials. This is accomplished by using a Wi-Fi version of the same trusted content mechanisms used on cable-based HDMI and DisplayPort connections.

Display resolution

Mandatory: ITU-T H.264 for HD and Ultra HD video; supports several profiles in transcoding and non-transcoding modes, including Constrained Baseline Profile, at levels ranging from 3.1 to 5.2
Optional: ITU-T H.265 for HD and Ultra HD video; supports several profiles in transcoding and non-transcoding modes, including Main Profile, Main 444, SCC-8 bit 444, Main 444 10, at levels ranging from 3.1 to 5.1

Audio

Mandated audio codec: Linear Pulse-Code Modulation 16 bits, 48 kHz sampling, 2 channels
Optional audio codecs, including:
  • LPCM mode 16 bits, 44.1 kHz sampling, 2 channels
  • Advanced Audio Coding modes
  • Dolby Advanced Codec 3 modes
  • E-AC-3
  • Dolby TrueHD, Dolby MAT modes
  • DTS-HD mode
  • MPEG-4 AAC and MPEG-H 3D Audio modes
  • AAC-ELDv2

    Hardware and software support

A device's wireless network adapter must support Wi-Fi Direct and Virtual Wi-Fi for it to work with Miracast; generally most adapters built since 2013 should meet the criteria. In Windows computers this can be checked by looking at the adapter's NDIS version which must be 6.3 or above. However Miracast support also depends on the software implementation by manufacturers. Most modern devices support Miracast, with notable exceptions being products from Google and Apple.

Windows and Linux PCs

Microsoft also added support for Miracast in Windows 8.1 and available on hardware with supported Miracast drivers from hardware manufacturers. Windows 10 and Windows 11 support Miracast transmitting along with User Input Back Channel support to allow for human interface devices abbreviated as HID, to also have wireless connectivity. The transmit feature is built-in from launch for all Miracast devices with no additional setup past using the WIN+K keystroke to pair with a compatible display sink.
Developers can also implement Miracast on top of the built-in Wi-Fi Direct support in Windows 7 and Windows 8. Windows 8.1 supports broadcasting/sending the screen via Miracast. Another way to support Miracast in Windows is with Intel's proprietary WiDi.
While Linux does not feature native support, several add-on software solutions exist. In the GNOME ecosystem, the GNOME Network Displays application has allowed for Miracast screen sharing. As part of the 2023 Google Summer of Code, an effort to integrate this as a feature in the GNOME Settings was announced, which would mean functionality would be had out of the box with that desktop environment.

Windows Wireless Display

Windows 11 and Windows 10 also have the ability to use Miracast to make a monitor display act as a secondary screen of another device. This feature can be set up in the Projecting to this PC setting. It requires the downloading of the optional Wireless Display add-in feature in Windows, which adds the UWP-based Wireless Display app and is launched on the receiving device.

Android

Miracast support was built into stock Android as of version 4.2 - as of January 2013, the LG Nexus 4 and Sony's Xperia Z, ZL, T and V officially supported the function, as did HTC One, Motorola in their Droid Maxx and Droid Ultra flagships, and Samsung in its Galaxy S III and Galaxy Note II under the moniker AllShare Cast. The Galaxy S4 uses Samsung Link for its implementation. Some devices such as the Nexus 7 don't support it due to hardware limitations.
Since Android 6.0 Marshmallow released in 2015, Google dropped Miracast support in favor of their own proprietary Google Cast protocol which was introduced with their Chromecast device. Despite this there are third-party Miracast apps for Android available. Many device manufacturers have retained Miracast support through their customized versions of Android. The performance and quality of the streamed video is dependent on the device's hardware.
Nokia devices, which ran a near-stock version of Android, originally did not support Miracast. However, Nokia 7 Plus, 8, 8 Sirocco, and 8.1 smartphones that have been upgraded to Android 9 or 10 are able to support Miracast, after enabling Wireless Display Certification in Developer Options. Devices such as Nokia 2.3, 2.4, 3.4, 5.4, and 8.3 5G have Miracast support enabled by default. The same option is present to stock Android as well, with Google describing it as based on the "Wi-Fi Alliance Wi-Fi Display Specification", but it tends to be useless as Miracast code was removed.

Televisions and dongles

televisions support Miracast where it is named Smart View. Miracast is also supported on LG smart TV models, some Toshiba TVs, Sharp, Philips, and Panasonic televisions and Blu-ray players. Sony Bravia models of televisions released between 2013 and 2020 normally have Miracast. The feature is named screen mirroring. Newer models with Android TV instead make use of the Google Cast protocol.
On 23 September 2014, Microsoft announced the Microsoft Wireless Display Adaptor, a USB-powered HDMI dongle for high definition televisions. Simple dongles such as these can be used to provide Miracast to a television that lacks the feature built-in.

Miscellaneous

Miracast over Infrastructure Connection Establishment Protocol allows the capabilities of Miracast but through a local network instead of directly. It has been supported in Microsoft Windows since Windows 10, version 1703. MS-MICE connects with computers that are connected to the network via secure Wi-Fi or through Ethernet.