HDMI-CEC Messages and Frames

Description

The CECFrame is a byte buffer that provides access to raw CEC bytes. CECFrame is guaranteed to be a complete CEC Message that has the necessary data blocks:

.

• The Header Data block (The byte that contains the initiator and destination address)
• The OpCode Data Block (The byte that contains the opcode).
• The Operand Data Block.(The bytes that contains the operands).

In most cases application need not access CECFrame directly, but manipulate the raw bytes through the Message API.

The Message API allows the application to send or receive high-level CEC message construct instead of raw bytes. Basically for each CEC message (such as ActiveSource), there is a C++ class implementation representing it. Each message class provides necessary getter and setter methods to access the properties of each message.

Modules
	HDMI-CEC Messages - Asynchronous Vs. Synchronous
	When messages converge on the logical buses, they are queued for sending opportunities on the physical bus. The waiting time for such send to complete, though short in most cases, can be problematic to some interactive real-time applications. It is recommended that the applications always send CEC messages asynchronously via the Connection API and use the listener APIs to monitor response messages or device state changes. The CEC library offers abundant APIs to facilitate such asynchronous implementation and the application is encouraged to make full use of them. Given the vast variance of HDMI-CEC support from the off-the-self media devices, it is not recommended that application wait for the response from a destination device. Even if the request message is sent out successfully, the destination device may choose to ignore the request. The recommended approach is again to send the request asynchronously and use the listener to monitor responses. Overall, given the asynchronous nature of HDMI-CEC, application should always opt to use Asynchronous APIs as first choice. And for same reasons, the RDK CEC library offers only limited support for Synchronous APIs.
	HDMI-CEC Messages and Frames Classes
	Described the details of High Level Class diagram and its functionalities.