Brief introduction of miracast protocol

Our wireless presentation system supports all three main streaming protocols, miracast, airplay and dlna. Miracast function is one of the important protocol among...
People use airplay to wirelessly stream the content from iPhone to the TV in the living room.

Our wireless presentation system supports all three main streaming protocols, miracast, airplay and dlna. Miracast function is one of the important protocol among them, relying on this protocol, we can easily share any content from android-based smart-devices to big screen easily without any installation of app, truly plug and play.

Brief introduction of Miracast

The rapid development of wireless technology and the emergence of various new technologies and protocols are dazzling. Miracast is the Wi-Fi CERTIFIED project announced by the Wi-Fi Alliance on September 19, 2012, which is a peer to peer based wireless streaming protocol. Products with this protocol can wireless mirrors video and images. for example, smart Android device can wireless connection and screen sharing videos or photos on TV without HDMI cables.

From Android4.2, this protocol have been integrate to the OS ( you can find in the settings, names as: Wifi display, Allshare cast, Mirroring screen, wireless display, etc., which may have different name due to the mobile phone manufacturers are different) . By using miracast devices, The HD video, and image of the smart phone can be wirelessly cast to larger display or other display devices like projector.

Miracast was formerly known as Wi-FiDisplay, an industry standard formulated by the Wi-Fi Alliance and widely supported. Currently, more than thousands of products have passed the certification, we called them miracast enabled device, including “source” devices (providing content sources) and “receiving” devices (final playback content, also called miracast receiver). It is the protocol with the largest user base among the three major current screen casting protocols [the other two is Airplay and DLNA].

The reasons for its widespread use are mainly due to the following points:

1. The underlying transmission is based on wifi-direct and WPS, which will not increase too much hardware cost.

2. The explosive growth of Android devices, Android 4.4 and above all support this protocol.

3.  Supports protected content streaming, so that the device can receive movies and other copyright-protected materials.

4. Each device automatically enables the new WPA2™ security protection to ensure the confidentiality of all multimedia content transmissions.

5. With the limitations of traditional wired projection, which can perform wireless projection anytime and anywhere.

6. With the advent of the era of real-time sharing of multi-player competitive content, there is an urgent need for a more convenient and efficient way to display, this protocol can be more convenient for us to interact.

Mirrors the screen image or streaming video on one device to another nearby device via Wi Fi network, and includes a variety of configurations, which can be easily and safely discovered and matched. With this technology, you can share multimedia content on mobile devices such as mobile phones and tablets to large-screen devices such as TVs. Sometimes our mobile phone screen casting to computers and TVs is not successful because our hardware devices do not support it. In addition to software support, there must be hardware support for screen casting.

Related documents about the protocol can be downloaded for free from:

https://www.wi-fi.org/file/wi-fi-display-technical-specification-v11

https://www.wi-fi.org/discover-wi-fi/miracast

Brief connection diagram of miracast

The figure above is the simplest miracast topology. The source is the sender and the sink is the receiver. The source sends its own audio and video data directly to the sink, and the sink receives and presents it.

Miracast technology can support one-to-many wireless data transmission, and multiple source terminals simultaneously transmit data to the sink terminal for display.

There is also the concept of GROUP in miracast. Each GROUP contains GO (GROUP OWER) and GC (GROUP CLIENT). GO is similar to AP’s function, providing WSC internal registration function, while GC performs WSC authentication.

The WFD devices need to go through, discover, establish a connection, negotiate capabilities, establish a session, and finally perform data transmission. The following steps are mainly required.

If some user-initiated operations need to be processed during data transmission, UIBC configuration is also required. This is a one-to-one process. For one-to-many, other users must also be added in the middle. After the data transmission is completed, it needs to be disconnected.

The importance of network card

In summary, the following parts need to be paid attention to during the development of miracast, namely the wireless network card part. A suitable network card is very important for future compatibility, success rate or audio and video quality. The WIFI-DIRECT part, this part Mainly carry out mutual discovery of devices, connection establishment, wireless connection time, GO and GC settings are completed in this step, RTSP part is the negotiation of various capabilities between devices, such as video format, resolution, frame Rate and other information, the A/V codec part, which is to decode and present the received video.

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