WiFi-Display协议学习

Miracast依赖的WiFi技术有：

WiFi-Direct，即WiFi P2P

Wi-Fi Protected Setup：帮助用户自动配置WiFi网络，添加WiFi网络设备。

11n/WMM/WPA2：其中，11n就是802.11n协议，它将11a和11g提供的Wi-Fi传输速率从56Mbps提升到300甚至600Mbps。WMM是Wi-Fi Multimedia的缩写，是一种针对实时视音频数据的QoS服务。而WPA2意为Wi-Fi Protected Acess第二版，主要用来给传输的数据进行加密保护。

WiFi Display连接步骤：

Establishment of WFD Connection using WiFi p2p

WFD Capability negotiation

HDCP Key negotiation

[b]1. Establishing a WFD Connection using Wi-Fi P2P[/b]

After the establishment of a P2P group, WFD Devices perform WFD Capability Negotiation， Subsequently, the IP address of the P2P client is assigned by the GO。

TCP Connection：

The TCP connection shall be initiated by the WFD Sink. The WFD Source plays the TCP server role and the WFD Sink plays the TCP client role. A Control Port (default is 7236 ) is used to establish and manage sessions between the WFD Source and WFD Sink。 The protocol running on the Control Port is RTSP。

[b]2 WFD Capability Negotiation[/b]

After a successful WFD Connection Setup (and establishment of a TCP connection), the WFD Capability Negotiation phase shall commence as specified herein. It takes place prior to the WFD Session establishment.



RTSP M1和M2主要协商Source和Sink都支持的RTSP methods

RTSP M3和M4主要协商Source和Sink在会话中使用的参数。

[b]3 Link Content Protection Setup（Optional）[/b]

the WFD Source establish the HDCP 2.0 session key with the WFD Sink. If the WFD Source and WFD Sink support HDCP system 2.0, both the WFD Source and the WFD Sink shall complete the HDCP 2.0 session key establishment before starting any RTP session used for WFD streaming.

If the HDCP 2.0 session key establishment fails, the WFD Sink supporting the HDCP system 2.0 may send an RTSP M7 request message to the WFD Source supporting the HDCP system 2.0 to start an RTP streaming. In this case, the WFD Source can only transmit audio and/or video content that ‘s not required to be protected by the HDCP system 2.0 to the WFD Sink.

[b]4 WFD Session Establishment[/b]

When an exchange of RTSP M7 request and response messages has successfully completed between the WFD Source and the WFD Sink, the WFD Session is established.



[b]5 WFD Source and WFD Sink session management Reference Model[/b]



[b]6 Audio & Video Payload Processing Reference Model[/b]



[b]7 总结[/b]

Main Steps:

WFD Device Discovery

WFD Service Discovery (Optional)

Device Selection

WFD Connection Setup

WFD Capability Negotiation

WFD Session Establishment

User Input Back Channel Setup (Optional)

Link Content Protection Setup (Optional)

Payload Control

WFD Source and WFD Sink standby (Optional)

WFD Session Teardown