WindRiver MediaLibrary 5.3 SDK开发教程

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《WindML 5.3开发指南》是WindRiver Systems针对其MediaLibrary SDK（媒体库软件开发工具包）编写的官方文档，版本号为5.3。该指南是专为开发者设计的，旨在帮助用户深入了解并掌握MediaLibrary SDK在WindRiver VxWorks操作系统下的开发流程、功能特性和最佳实践。该文档的核心内容包括了对MediaLibrary API的详细说明，涵盖了媒体数据管理、存储、检索、播放和编码等功能模块的使用方法。开发者可以借此了解到如何高效地集成MediaLibrary到自己的应用项目中，实现多媒体内容的管理和处理。指南中还可能包含对VxWorks平台的兼容性信息，以及与硬件设备的接口配置指南。版权方面，所有内容受2009年WindRiver Systems, Inc.的版权保护，未经书面许可，禁止任何形式的复制或传输。文中提及的WindRiver、Tornado和VxWorks都是该公司的注册商标。关于第三方商标的使用，指南会指引读者查看WindRiver官方网站（www.windriver.com）的商标政策以获取更多信息。特别值得注意的是，该SDK可能包含了来自第三方的软件许可，这些许可通常会在产品安装目录中的"3rd_party_licensor_notice.pdf"文件中提供相关声明和注意事项。这意味着在使用过程中，开发者需要遵守这些额外的条款和规定。此外，文档可能引用或链接到第三方出版物或网站，仅作为信息参考源，并不代表WindRiver Systems对这些第三方资料的准确性或完整性承担责任。因此，在依赖这些外部资源时，开发者应自行评估其可靠性。《WindML 5.3开发指南》是一份全面而深入的文档，对于想要利用WindRiver MediaLibrary SDK进行VxWorks平台上多媒体应用开发的工程师来说，它是不可或缺的参考资料。通过阅读和遵循其中的指导，开发者能够提升开发效率，确保应用的稳定性和兼容性。

Wind River Media Library

SDK Programmer's Guide, 5.3

This chapter assumes a basic understanding of the Workbench project types—

kernel image, DKM, and RTP—which are fully documented in the Wind River

Workbench User’s Guide. The purpose of this chapter is to describe how to configure

and build them specifically for Media Library.

The four different types of projects used with Media Library applications are

summarized in this section. How you combine these projects is discussed in

2.2 Choosing a Use Case, p.7.

Media Library Downloadable Kernel Project

The Media Library downloadable kernel project is a DKM project that is used to create

the pair of kernel-mode Media Library archives. These library archives provide the

following functionality:

■

They provide all of the kernel-mode SDK and DDK Media Library objects that

are used by kernel mode applications.

■

They provide the low-level kernel drivers, which that are used by both

kernel-mode and user-mode (RTP) applications. These low level drivers are

sometimes referred to as "iodrv" drivers in other locations (such as in the

driver database files).

Once the library archives are built, the objects from those archives are then linked

into the VxWorks image and application (if the application is linked separately

from the VxWorks image).

Creating and configuring the project that is used to create the library archives must

be done in Workbench. The project for the libraries is created as a DKM library

project (rather than as a DKM application project). It is configured to include the

code that implements and initializes the low-level drivers, and whatever specific

functionality is required by the kernel-mode user application. Once the library

archives are built, those modules are then linked into the VxWorks image.

Consequently, the library archives must be created and built before the VxWorks

image project is built.

Creating and configuring the library archives must be done in Workbench (you

cannot use the command line to do this). The configuration is then saved to a file

for that project, and the remaining link and build operations are available equally

from Workbench or the command line.

VxWorks Image Project for your BSP

A VxWorks Image Project is used to configure and build a VxWorks kernel image to

boot your target. Kernel modules, applications, libraries, and data files can be

linked into a single image at compile time, or downloaded separately at run-time.

For Media Library applications, the image is built with the library archives

described above. If certain, device-related aspects of the configuration change, the

library project must be rebuilt with the new configuration; and the image must

then be rebuilt to include the changes. Not all changes to the library configuration

require the image to be rebuilt. For details, see 2.4 Configuring the VxWorks Image,

p.19 and Configure the Media Library archives., p.16.

2 Configuring and Building Media Library

2.2 Choosing a Use Case

Media Library User Application

The Media Library application can be created as a separate module or as part of the

VxWorks image. It can linked at compile time, or downloaded and linked at

run-time. It can be created to run in kernel space or in user space. Your choices, and

the details and benefits of each are described in 2.2 Choosing a Use Case, p.7.

Real-time Process Library Project

If the user application is created as an RTP project, which runs in user space, then

an additional pair of Media Library archives must also be created, this time as an

RTP project. The RTP application is linked against these Media Library RTP library

archives at compile time, and the application is downloaded at run-time.

You only need to create this additional libraries if your Media Library application

is an RTP project. If the RTP library archives are created, the library configuration

of the device types and device names must match that of the DKM library

configuration that is used to build the VxWorks image. However, characteristics of

the devices can differ, as described in Configure the Media Library archives., p.16.

Symmetric Multiprocessor Support

VxWorks includes facilities that support symmetric multiprocessing (SMP).

VxWorks SMP is a separately purchased product. Media Library is SMP-ready

and runs correctly on SMP hardware. For technical information on SMP, see the

VxWorks Kernel Programmer's Guide: VxWorks SMP.

For more technical information on SMP, see the VxWorks Kernel Programmer's

Guide: VxWorks SMP. For purchasing details, please contact your local Wind River

representative.

2.2 Choosing a Use Case

There are several standard configurations that you can use to create, link, build,

and run a Media Library application. These configurations are called use cases, to

distinguish them from the configurations that apply to the Media Library archives.

Each use case listed in this section includes the following:

■

a brief description of how the application is built and run

■

a diagram illustrating the relationship of the modules (dotted arrows indicate

linking, solid arrows indicate output)

■

the advantages and disadvantages of choosing the use case

■

the steps required to create and build the projects for the use case

NOTE: For all use cases, the VxWorks image is always linked against the library

archives when the image is built (meaning, at compile time). What differs in the

use cases is primarily how the application is linked against the library archives.

Wind River Media Library

SDK Programmer's Guide, 5.3

without the drawbacks of each. During development, you can choose to download

the application and link to the image at run-time. Because you only need to prelink

to the library archives (and not to the VxWorks image), the test and build cycle is

somewhat shortened and you do not need to reboot the VxWorks target.

The disadvantages of this use case are:

■

the application must be downloaded before you can run it

■

the application is not as isolated as 2.2.3 Kernel-Mode Run-time Application, p.10

Building this Application

To build a kernel-mode compile-time application, proceed as follows:

1. Define and build the pair of library archives as a

VxWorks Downloadable Kernel Module Project, as described in

2.3.1 Configuring the Media Library Archives, p.15.

2. Create a VxWorks image project, and configure it as described in

2.4.3 Configuring VxWorks, p.20.Include the required component and the

optional Compile-time component.

3. Build the VxWorks image, as described in the Wind River Workbench User’s

Guide.

4. Create, configure, and build the application project as described in 2.5 Using

the Media Library Application Templates, p.22. In Step 3, choose the

VxWorks Downloadable Kernel Module Project. In Step 4, choose

Media Library Application Support.

5. Download and run the application, proj_name.out, as described in Step 8.

2.2.3 Kernel-Mode Run-time Application

Figure 2-3 shows a Media Library project in which the application is created as a

DKM project that contains only application code. It is not linked against either the

library archives or the VxWorks image until it is executed on your target at

run-time.

The VxWorks image is built with full Media Library functionality, as configured in

the library archives, and is capable of supporting any Media Library application.

Advantages and Disadvantages

This use case offers the following advantages:

■

the VxWorks image can support any Media Library application

■

application can be independently recompiled and downloaded

■

application independence allows shorter build and test cycles

Because the application module is completely isolated from the library archives

and VxWWorks image, this use case is especially useful during development and

testing.

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