||The neutrality of this article is disputed. (August 2013)|
Miracast is a certification program of the Wi-Fi Alliance based on their Wifi-Display specification. It defines a protocol to connect an external monitor or TV to a device, and therefore can roughly be described as "HDMI over Wifi", replacing the cable from the computer to the display.
It is peer-to-peer, and wireless, using a Wi-Fi Direct connection. It allows sending up to 1080p HD video and 5.1 surround sound (AAC and AC3 are optional codecs, mandated codec is linear pulse-code modulation — 16 bits 48 kHz 2 channels). 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. Adapters are available that plug into HDMI or USB ports that enable Non-Miracast devices to connect via Miracast. The developer responsible for the implementation of Miracast in Linux does not recommend the standard as the technology is "horrible".
Nvidia announced support for it in their Tegra 3 platform, and Freescale Semiconductor, Texas Instruments, Qualcomm, Marvell Technology Group and other chip vendors have also announced their plans to support it.
Both devices (the sender and the receiver) need to be Miracast certified for the technology to work. However, to stream music and movies to a non-certified device there will be Miracast adapters available that plug into HDMI or USB ports.
As of January 8, 2013, the LG Nexus 4 and Sony's Xperia Z, ZL, T and V officially support the function, as does HTC One, Motorola in their Droid Maxx & 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. In October 2013, BlackBerry released its 10.2.1 update to most of the existing BlackBerry 10 devices available at that time. As of March 2015, the BlackBerry Q10, Q5, Z30, and later models support Miracast streaming; the BlackBerry Z10 does not support Miracast, due to hardware limitations.
Microsoft also added support for Miracast in Windows 8.1 (announced this in June 2013). This functionality first became available in the Windows 8.1 Preview, and is available on hardware with supported Miracast drivers from hardware (GPU) manufacturers such as those listed above.
The WDTV Live Streaming Media Player added Miracast support with firmware version 2.02.32
The Amazon Fire TV Stick, which started shipping on 19 November 2014, also supports Miracast.
On 28 July 2013, Google announced the availability of the Chromecast powered by a Marvell DE3005-A1, but despite the similarity in name and Google's early support of Miracast in Android, the Chromecast does not support Miracast.
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 (DRM) 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.
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.
Miracast is limited to Wi-Fi Direct supported devices. Comparing to other IP-based screen mirroring applications such as Splashtop, MirrorOp, VNC and RDP, Miracast cannot run on all IP networks such as conventional Wi-Fi, wired Ethernet, powerline networking and Internet, but those IP-based screen mirroring applications can run on Wi-Fi Direct. The Miracast standard also has "optional components" such as Wireless Multimedia Extensions (WMM). The use of optional components in "standards" often causes issues if one vendor supports the options components and another does not. Its reliance on Wi-Fi Direct also reduces the attractiveness of the technology in enterprise environments.
- the specification is only available on payment of a large amount of money.
- hardware is barely available; in February 2014, the only working chip was Intel's 7260-WLAN-Chip.
- The developer considers the technology "horrible". Filters are sent which define properties of the hardware, e.g. the screen resolution. This boils down to an enormous amount of data sent which makes its challenging to find the correct peering device. IPv4 including DHCP is used as internet protocol, not the new IPv6. To transfer contents the sender and receiver device should be done, but sometimes this happens spontaneously without a possibility to change it afterwards. The streaming is controlled via the RTSP. The disadvantage is that the receiver explicitly needs to request the data transfer from the sender - instead of the sender just starting the transfer.
Certification does not mandate a maximum latency (i.e. the time between display of picture on the source and display of the mirrored image on the sync display).
The Wi-Fi Alliance certified the Wi-Fi Direct protocol in October 2010, and the first smartphone to ship with Wi-Fi Direct was the Samsung Galaxy S II, released in February 2011. All new Android devices starting with Android 4.0x (Ice Cream Sandwich) support Wi-Fi Direct. Desktop PC hardware can be upgraded with new Wi-Fi-Direct-compatible hardware. Only embedded devices will not be able to be upgraded.
There are serious incompatibilities between Miracast devices, i.e. being Miracast compatible does not mean devices can talk to each other. On the internet huge lists are collected with devices compatible to each other.
Miracast support is built into Android 4.2 or later  and starting with Android 4.4, devices can be certified to the Wi-Fi Alliance Display Specification as Miracast compatible. Miracast is also built into BlackBerry 10.2.1 devices and Microsoft Windows Phone 8.1 and Windows 8.1 although developers can implement Miracast on top of the built-in Wi-Fi Direct support in Windows 7 and Windows 8. Another way to support Miracast in Windows is with Intel's proprietary WiDi v3.5 or above. Apple supports its own Peer-to-peer AirPlay instead of Miracast on OS X. For the Linux desktop there exists MiracleCast which provides early support for miracast but is not tied to that single protocol. A software based Miracast receiver for Windows 8.1, AirServer Universal was made available on October 31, 2014 by App Dynamic.
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