DirectShow作为多媒体框架，通过职责分离将复杂任务分解为一系列过滤器，每个过滤器专注于特定任务如数据抓取、解码和渲染等。此外，DirectShow提供了一个成熟的抽象层，允许开发者在不改变接口的情况下轻松替换组件，例如从软件解码器切换到硬件解码器。DirectShow还内置了许多常用的多媒体功能，简化了开发过程。
In this post, I'll summarize some features that make directshow stand out, from a developer's point of view.
The architecture of directshow is:
The core of directshow framework is the box in the center.
1. separation of concerns
Directshow divides a complex media rendering task into a bunch of smaller tasks, organized as different filters. Each filter has its own concentration, e.g., grabbing data from source media file, decoding data, rendering the data on display. It's more natural and easier for our brain to resolve complex problems in smaller steps, one by one. Another benefit of this breakdown structure is we can perform unit test on smaller component more easily.
2. mature abstraction layer
Directshow provides a mature abstraction layer on top of sub-tasks' concrete implementations ( Adapter pattern). The existence of the abstraction layer makes our project easier to manage. The cost for dealing with changes can be minimized. For example, we can have one guy tries to implement a hardware based decoder filter. And before his filter is available, other guys in charge of other parts can use a software based decoder filter instead. After the hardware based filter is done, it's hopeful to replace the software based filter without requiring changes on other parts because interfaces of both filters are the same.
3. built-in multimedia functions
Besides being a sophisticated core framework, directshow also contains a lot of commonly used multimedia features like common media type decoders, some splitters, and multi-stream synchronizer. With these features built-in, we developers' life will be a lot easier.
References
MSDN: Directshow System Overview
http://en.wikipedia.org/wiki/DirectShow
The architecture of directshow is:
The core of directshow framework is the box in the center.
1. separation of concerns
Directshow divides a complex media rendering task into a bunch of smaller tasks, organized as different filters. Each filter has its own concentration, e.g., grabbing data from source media file, decoding data, rendering the data on display. It's more natural and easier for our brain to resolve complex problems in smaller steps, one by one. Another benefit of this breakdown structure is we can perform unit test on smaller component more easily.
2. mature abstraction layer
Directshow provides a mature abstraction layer on top of sub-tasks' concrete implementations ( Adapter pattern). The existence of the abstraction layer makes our project easier to manage. The cost for dealing with changes can be minimized. For example, we can have one guy tries to implement a hardware based decoder filter. And before his filter is available, other guys in charge of other parts can use a software based decoder filter instead. After the hardware based filter is done, it's hopeful to replace the software based filter without requiring changes on other parts because interfaces of both filters are the same.
3. built-in multimedia functions
Besides being a sophisticated core framework, directshow also contains a lot of commonly used multimedia features like common media type decoders, some splitters, and multi-stream synchronizer. With these features built-in, we developers' life will be a lot easier.
References
MSDN: Directshow System Overview
http://en.wikipedia.org/wiki/DirectShow
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