OpenMax IL 有四個部分組成：
客戶端(Client)：OpenMax IL的調用者
組件(Component)：OpenMax IL的單元，每一個組件實現一種功能
端口(Port)：組件的輸入輸出接口
隧道化(Tunneled)：讓兩個組件直接連接的方式
OpenMax IL 中重要的組成部分是component，component是OpenMax IL實現的核心內容，一個組件以輸入、輸出端口爲接口，端口可以被連接到另一個組件上。外部對組件可以發送命令，還進行設置/獲取參數、配置等內容。component的端口可以包含緩衝區(Buffer)的隊列。
OpenMAL IL的客戶端，通過調用四個OpenMAL IL組件，實現了一個功能。四個組件分別是Source組件、Host組件、Accelerator組件和Sink組件。Source組件只有一個輸出端口;而Host組件有一個輸入端口和一個輸出端口;Accelerator組件具有一個輸入端口，調用了硬件的編解碼器，加速主要體現在這個環節上。Accelerator組件和Sink組件通過私有通訊方式在內部進行連接，沒有經過明確的組件端口。如下圖：
組件的處理的核心內容是：通過輸入端口消耗Buffer，通過輸出端口填充Buffer，由此多組件相聯接可以構成流式的處理。
component state有如下，具體定義在OMX_Core.h
framework/base/include/media/libstagefright/openmax/OMX_Core.h
typedef enum OMX_STATETYPE
{
OMX_StateInvalid, /**< component has detected that it's internal data
structures are corrupted to the point that
it cannot determine it's state properly */
OMX_StateLoaded, /**< component has been loaded but has not completed
initialization. The OMX_SetParameter macro
and the OMX_GetParameter macro are the only
valid macros allowed to be sent to the
component in this state. */
OMX_StateIdle, /**< component initialization has been completed
successfully and the component is ready to
to start. */
OMX_StateExecuting, /**< component has accepted the start command and
is processing data (if data is available) */
OMX_StatePause, /**< component has received pause command */
OMX_StateWaitForResources, /**< component is waiting for resources, either after
preemption or before it gets the resources requested.
See specification for complete details. */
OMX_StateKhronosExtensions = 0x6F000000, /**< Reserved region for introducing Khronos Standard Extensions */
OMX_StateVendorStartUnused = 0x7F000000, /**< Reserved region for introducing Vendor Extensions */
OMX_StateMax = 0X7FFFFFFF
} OMX_STATETYPE;
component在LOADER狀態下，只能建立它本身一些屬性和配置信息，客戶端能做什麼呢？客戶端可以發* SetParameters/GetParameters and SetConfig/GetConfig這些command給component，以便以後component記錄下這些parameter和configuration的變化。在IDLE狀態下，就可以分得buffer之類的資源，但是不能操作這些buffer直到component處於Executing狀態下。
component state 如何轉換呢？
一般change state可以通過OMX_SendCommand的方式通知給component，格式如下：
OMX_SendCommand( hComponent, Cmd,mParam,pCmdData)
hComponent:執行該command的component
Cmd:給component執行的command
mParam:執行command的一些參數值
如客戶端發給component：mOMX->sendCommand(mNode, OMX_CommandStateSet, OMX_StateIdle);
說到command 那就列舉下有哪些command吧：
coder在如下路徑：
framework/base/include/media/libstagefright/openmax/OMX_Core.h
typedef enum OMX_COMMANDTYPE
{
OMX_CommandStateSet, /**< Change the component state */
OMX_CommandFlush, /**< Flush the data queue(s) of a component */
OMX_CommandPortDisable, /**< Disable a port on a component. */
OMX_CommandPortEnable, /**< Enable a port on a component. */
OMX_CommandMarkBuffer, /**< Mark a component/buffer for observation */
OMX_CommandKhronosExtensions = 0x6F000000, /**< Reserved region for introducing Khronos Standard Extensions */
OMX_CommandVendorStartUnused = 0x7F000000, /**< Reserved region for introducing Vendor Extensions */
OMX_CommandMax = 0X7FFFFFFF
} OMX_COMMANDTYPE;
具體command如何傳到component，可以參考本博的OMXCodec與OMX事件處理流程
http://blog.csdn.net/tjy1985/article/details/7397752
