Video +Renderer Overview

Purpose

The Video Renderer renders video to a graphics +surface. The Video Renderer can be used by video decoders, video post-processors +and video controllers. It can also be used to implement the ECam +viewfinder using a graphics surface.

The Video Renderer has +two modes: timed and non-timed. In timed mode, the Video Renderer renders +a frame at a specific time. In non-timed mode, the Video Renderer renders +a frame immediately.

On the Symbian platform, ScreenPlay (also +known as the New Graphics Architecture or NGA) enables rendering to a graphics +surface. The Video Renderer can only be used in conjunction with ScreenPlay. +The Video Renderer does not contain any video or graphics processing software. +All operations that are needed to display video content on the screen are +handled by the Graphics +Composition Components.

The Video Renderer component is classified +as Optional Replaceable. This means that device creators can either substitute +it with their own implementation or remove it if they do not want to use it.

Required background

To understand the Video Renderer, +the reader must be familiar with the following:

Graphics +Surfaces

Architecture

The Video Renderer can be implemented +in two different ways, as shown in the following diagram:

+ The two Video Renderer architectures + +

Note: For simplicity, only the Multimedia Framework client/controller +thread boundary has been shown; other thread boundaries may exist.

In +both architectures, the Video +Client API (CVideoPlayerUtility2) is responsible +for retrieving graphics surface handles from the video player controller and +registering them with the Window +Server. The difference in the two approaches is in the implementation +of the video adaptation and the video player controller:

Video adaptation +approach

The video adaptation uses the Video Renderer to create +and manage graphics surfaces and handle video rendering. The video player +controller simply passes surface information between DevVideoPlay and +the client. An example of this is the Symbian reference AVI player controller +and XVid decoder. Symbian recommends this approach for +new implementations.
Video player controller +approach

The video player controller uses the Video Renderer +to create and manage graphics surfaces, and handle video rendering and timing. +This approach is suitable for implementations where DevVideoPlay is only used +as a codec interface or where DevVideoPlay is not used.

In both architectures, the Surface +Update component provides a communication channel between the Video +Renderer and the composition engine.

APIs

The Video Renderer component contains the +following DLL with its associated APIs:

+ + + +DLL +Description + + + + +

videorenderer.dll

The functionality of the Video Renderer is provided by the following +key classes:

CVideoRenderer - +a utility class for rendering video to graphics surfaces on behalf of a client.
MVideoRendererObserver - +an observer class that provides notifications about the availability and status +of buffers submitted for rendering.
TVideoFrameBuffer - +represents a buffer for a single decoded video picture.

The Video Renderer also uses a resource file (videorenderer.rss) +to store supported pixel formats and timed mode values. For more information, +see Video Renderer +Resource File.

+ + + +

Typical uses

The Video Renderer is used for the +following:

Creating a surface for +video rendering
Supplying buffers to +decode video frames into
Rendering a buffer on +the display (timed or non-timed)
Destroying a surface.