Broadcom Nexus学习(五)系统结构

1. Nexus 结构

Nexus分为三层结构：Application， Nexus， Magnum。

（1）Application and Middleware

应用和中间件

（2）Nexus

上层模块，为应用开发提供各种接口。

Nexus中包括：各个模块，驱动，回调函数，消息，计时器等系统信息。

• Interfaces: From the application’s perspective, Nexus is a high-level API for DTVs and set-top boxes. This
     is represented as a collection of interconnected Nexus Interfaces. An Interface is a set of function
    signatures (that is, prototypes), along with their structures and enums, that present a feature.
• Modules: A collection of code with a common state and synchronization. It provides the implementation
   for one or more Nexus Interfaces.
• Base: Provides OS abstraction required for Nexus architecture rules, including creating tasks, requesting
   task callbacks for timers and events, and queuing callbacks to applications. A Nexus Base is analogous to
  Magnum’s Base Modules, except at a higher level.
• Platforms: Collects all the Nexus Interfaces available on a system into a cohesive whole. It also provides
   OS driver code, board configuration, along with a build system. A Platform can be customized to meet a
  user’s configuration and integration needs.

（3）Magnum

底层核心模块，提供硬件的接口。

2. Nexus组件

Nexus的组件很多，比较重要的有：

（1）playback（解码核心）

（2）playpump（playback的engine）

（3）record（重新编码核心）

（4）recpump（record的engine）

（5）videoDecoder  videoEncoder

（6）audioDecoder  audioEncoder

（7）stream Mux

（8）A/V Muxer

（9）display  （物理设备？？）

（10）window（虚拟设备？？）

（11）audioMix（混音器）

（12）pidChannel

（13）stcChannel

3. 实例123

code：

main() {
// open Interfaces
videoDecoder = NEXUS_VideoDecoder_Open(0, NULL);
display = NEXUS_Display_Open(0, NULL);
window = NEXUS_VideoWindow_Open(display, 0);
component = NEXUS_ComponentOutput_Open(0, NULL);
// make connections
NEXUS_Display_AddOutput(display, NEXUS_ComponentOutput_GetConnector(component));
NEXUS_VideoWindow_AddInput(window,NEXUS_VideoDecoder_GetConnector(videoDecoder));
startSettings.pidChannel = NEXUS_PidChannel_Open(NEXUS_ParserBand_e0, 0x21, NULL);
// start video decode
NEXUS_VideoDecoder_Start(videoDecoder, &startSettings);
}

4. Nexus Module 交互

5. 一些实例的数据流图