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Multimedia flow apps in Microsoft Windows CE 3.0 (on)

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Multimedia flow application in Microsoft Windows CE 3.0

Microsoft Corporation

June 2000

Summary: This article discusses multimedia streaming of Windows Media® components based on Microsoft® Windows® CE DirectX Platform Adaptation Kit 1.2 (Different Microsoft Windows versions.

Contents

Overview

Technical Fundamentals

Windows Media Player Control

Windows Media Technologies

Windows Media Formats

Windows Media Features, WINDOWS Media Features

Windows Media Protocols

Windows Media Codecs

DirectShow

Filter Graph Manager

Filters

For more information

Foreword

The digital revolution has brought a storm that consumers have brought a storm. Hundreds of channels brought by the digital cable of the connecting machine top box can be replaced with the original product. The portable digital audio player provides longer music playback time and provides better sound quality than tape players. The fundamental change of consumer electronics is coming from new phenomena and natural evolution. Due to this change, in the near future, PC will no longer be the only knowledge of digital multimedia sources, has been recognized.

Many new consumer goods are accepted by consumers through digital music, movies, television and other multimedia content. Even with the best compression mode (such as Microsoft Windows Media? Audio), the amount of data of multimedia content is still large. For example, the compression ratio is 120kbits / sec, and the digital audio needs to store a four-minute song with 3.6MB. If you store a two-hour movie, the digital video requires 270MB for 300 kbits / sec, 4 KBITS / Sec, the 3.6GB!

Huge media files can be solved by the following two ways:

Download the entire file to the local memory and process the storage data block sequence (local stream) or processes the entire storage file (non-flow). Or download and process a separate data block sequence (network stream). The network stream can also be processed by the media data created by the server without being stored as a separate file.

Send the next related small amount of data requires fast processing and playback work (not all data sets) because multimedia content is a continuous digital data without rugged long-term time coupling. In other words, the sound block of a song or the pixels in the video frame can be independently processed and played, at least when there is enough time, they are separated. This allows an independent data in time groups to be abandoned. These data will be displayed in different times in the independent time sequence in any process in either process by coding, transmitting, and playback. This method of time sequence of this transmit block is temporarily weakened to the data of the client device being streamed. Client devices need enough cache packages to prevent server, network, client interrupt, or create, send, and time correction.

How do Windows CEs suitable for this description through the Windows Media component? Windows CE DirectX Platform Adaptation Kit 1.2 (OR DXPAK) can provide multimedia playback and PC-based streaming capabilities, but there is no more available structural components. These components operate on a high-performance CPU that supports Windows CE (X86, MIPS R4300 and Compatible, And SH4, Available Now With Dxpak 1.1; ARM, STRONARM, AND INTEGER MIPS Planned For DxPak 1.2). The modular design of Windows Media Components for Windows CE allows you to have enough elastic to select those components on your platform. When using Platform Builder to create an operating system image for your hardware, you can decide if you want a special DirectX or user interface component, communication protocol, or file system. This flexibility allows you to install the technology you need to your platform, save space, reduce complexity. Windows CE 3.0 with The DirectX Platform Adaptation Kit 1.2 (or DXPAK) provides a complete solution for developing a kill-level consumer tool or application. The system that provides adequate component sets for digital multimedia devices is full of vitality, powerful real-time operating systems.

Technical Fundamentals

technical foundation

The DirectShow section of Microsoft DirectX provides a basic platform for multimedia services on Windows CE. Many multimedia applications that can be used alone, in fact, many companies are doing this, but this is not the only way out. A communication structure is above DirectShow, making the application developer's work in advance. Their structure meets the following chart: (MultiMedia1.gif)

Figure 1. Communication Structure Based on DirectShow

Communication structure based on DirectShow

The user can see the top layer of the chart is: web browser or other applications. The application can embed the Window Media Player (WMP) control, or you can connect the interface of DirectShow via COM. In both scenarios, DirectShow manages data flow from source to hardware. Drive developers are the most concerned about the underlying. The application developer is required to have: WMP control, WMT and DirectShow.

Windows Media Player Control

As an ActiveX control and other content, there is a web page. The WMP control is a universal tool that can handle local and streaming multimedia files. It supports all mainstream media file formats, including Windows Media format files (ASF, ASX, WMA, WMX, WMV, WVX, WM, And WMX Files), MPEG Format (MPG and MPE Files), and audio formats, for example, MP3, MIDI, WAV, And AIFF, and MultiMedia Format Avi Files. All of these file formats use WMP controls to be flown from the local storage file, and when combined with Microsoft Windows Media technology, it will support operations over the network. DirectX Platform Adaptation Kit 1.2 (OR DXPAK) supports controls for Windows Media Player 6.4.

Placing The WMP Control in A Web Page

Place WMP controls in the web page

Use the Object tag to embed an ActiveX object into a web page. The following example shows how to insert the WMP control using the Object tag.

ClassID = "CLSID: 22D6F312-B0F6-11D0-94AB-0080C74C7E95"

TYPE = "Application / X-oleObject"

Width = "320"

HEIGHT = "240"

STYLE = "Position: Absolute;

LEFT: 50px;

TOP: 50px; "

>

Value = "http://example.microsoft.com/media/sample.asf">

The ID attribute of the Object tag specifies a name for the WMP object, which will be applied to the scripting language. The classID property is that IE must create this object in the page, and this string will always be listed in the previous example. The Type property indicates that the object embedded in the browser is an ActiveX control. Optional width and height properties set the size of the WMP object form. Style property allows you to specify any location of the object form to the web page.

All WMP features are called via Microsoft Jscript Web Scripting Language. Other scripting languages ​​are usually not supported.

Note that the CodeBase property in the Object flag does not exist. CodeBase specifies a URL if there is no WMP control on the user system, then download it according to this URL. This feature is not supported on CE. The WMP control must be included in your OS image if it can be applied to your program.

PARAM marks have two properties: the first is the name of the nature, the second, specifies the value of this nature. When they are created,

PARAM tag initializes the WMP object. In this example, the first PARAM tag set the file name nature as a URL http://example.microsoft.com/media/sample.ASF, defined the file will be played by the WMP control. This value can also be set to the path of the local media file, such as C: /sample.asx. The following PARAM tag specifies whether the playback control and status bar of the object are visible. These foundations can be hidden replacement so that you can customize the appearance of the WMP control and user interface items.

After you create an object and specify the correct file name, you can see the WMP control in your web page.

Here are three other HTML tags that are used to include audio and video in a web page - embedded object tag , image tag , and Anchor tag . Tag is created by the browser plugin supported by Netscape. Netscape does not support embed objects with the tag, if you want to maintain compatibility with the Netscape browser you should use this tag. Although tag can be used to include video CLIPs in the web page, it can use a limited number of media types (MPEG, QT, And Avi Files.). Tag does not provide access to any WMP control properties and do not support all audio media. In order to use all the features of all WMP controls, tag is not recommended.

label can also be used to create a media connection. The media is played by the application or browser specified by the media type. Tags cannot be embedded in the media in the web page as the or tag. A key points out that the WMP control is different from Windows Media Player. As a result, all Internet media content can be mastered by the WMP control. An example uses the tag for content access. Typically, when a user browses the Internet with a PC, click on a connection to a media file, and the Windows Media Player application appears on the desktop, control the media content from the browser to the player. If you want to create a device or application support all existing Internet Media Content, you must be aware of Control Recognizes, and correctly master all the ways of passing content. The WMPHLPR example contained in DXPAK 1.2 provides an example of how to make WMP controls back to the media by accessing labels. When a user clicks on a media connection, the browser Navigates This page of the page. Media files are passed to the control and play back in the browser. This behavior is very useful to set-top boxes, Internet access devices, or other devices that are limited or not running through a single window. Windows Media Player Control for Windows CE contains some differences in tiny controls with the controls on the X86-Based PCS. The driving force is included in a subset of desktop WMP controls, providing a small, robust, compressed WMP control for partial features for embedded devices. In addition, WMP Control for Windows CE also supports a subset of desktop control properties, methods, and events. Some properties, methods, and events are not included in the WMP controls of the CE version, as they do not actually value for non-PC devices, such as set top boxes and music automatic cat. Microsoft NetShow? Player Control does not support backward compatibility, and since all NetShow features are compressed into the WMP control. Some UI features are not supported, for example, Context Menu, Display Panel, Closed Captioning Panel, and Go To Bar, but can be implemented in a web page in a web page.

Microsoft PowerPoint® (PPT) stream and heat zone ASP features are not supported. By using URL Flipping, when playing slideshows or playing other Graphics in other Frames, it is possible to play media through the WMP control. Clickable HotSpots can convert images or Video Clips in the connection or Script Locations, and can implement the URL script command appropriately implemented some Times in an ASP file.

Windows Media Technologies

Window Media Technologies (WMT) is a set of COM interfaces and CODECs to support server / client applications, audio, video streams, and similar streaming script commands.

Today, Windows CE 3.0 with the DirectX Platform Adaptation Kit 1.2 (or DXPAK) supports Windows Media Technologies Version 4.1 Components. These components support clients using advanced Windows Media formats and World-Class Codecs playback, such as Windows Media Audio, Microsoft MPEG-4 Video, And Sipro Acelp.Net Low Bit-Rate Speech.

The following will focus on Formats, Features, Protocols, and Codecs supported by WMT ON Windows CE. Sometimes, Windows CE supports WMT and other versions of Windows vary. In this case, their differences and workspaces will be discussed. Windows Media Formats

WMT uses Advanced Streaming Format (ASF) to store and transfer data. ASF is an application-level multimedia transfer file format (can be seen as a Wire or Transfer Control Format) to schedule and organize synchronous multimedia data. ASF supports media data to transmit in a variety of network types, network bandwidths, and protocols. This is the optimization scheme for multimedia packets in low speed networks and broadband networks.

Windows CE also supports Advanced Stream Redirector V3 (ASX) and Windows Media Station. The ASX metad file provides a mechanism for the client supports the superconnect stream, supports multiple protocols for source content, and also supports the ROLLOVER rules, and clients handle them like supporting media playlists.

The Microsoft Windows Media Station End File Services will open a special channel for channels you want access to ASF customers. The mode of accessing a channel and the TV to access a broadcast channel is similar. This yuan file is supported by Multicasting.

Windows Media Features, WINDOWS Media Features

Windows CE Support WMT Client DirectShow Filters uses UDP, TCP, and HTTP protocols to play ASF streams (Windows Media Protocols will be described in the next section. Windows CE WMT supports Smart Streaming, which uses Multi-Data rates to encode ASF files, and multimedia streams create an ASF file at different BITs, clients, and server negotiate an appropriate stream. The server relies on playback conditions from moving adjustment streams, and can select multimedia video stream based on network bandwidth.

With Smart Street, the Windows CE WMT client is based on the available network bandwidth dynamically, and only one algorithm can only download the keyframe in the case where the play is smooth. If necessary, the WMT client can allow the server to send only audio without sending a video package. In the case of limited bandwidth, the audio always maintains the highest priority, which is the user experience. If the condition of the network bandwidth has improved, WMT gradually increases video Bit-Rate to return to the best viewing effect. In addition, if time allows, the WMT UDP allows the client to request a lost package to the server. Finally, when the client sends an ASX control command to the server side, WMT also provides Asx Event-Driven Stream conversion.

Windows CE WMT does not support old ASX V2.0 or V1.0 format. All of these earlier versions are included in ASX V3.0. In addition, PreviewDuration, Banner, or Logo Asx Elements does not support Windows CE. The Preview method can be implemented by using the WMP control in the application, if the play control can be accessed through a scripting language. The features of Banner and Logo Elements can be implemented using DHTML and Scripting.

CE provides support for Authentication. Authentication gets the user's confirmation before any information exchange. When the user sends a request to the server being confirmed successfully, the server determines the identity of the client. For any particular interaction, both clients and servers must come with an agreement. WMT supports the following two protocols, based on HTTP to the Internet application, NTLM is suitable for intranet applications.

On the desktop computer, NTLM when the user logs in

Use custom authentication information, which requires servers and clients within the same or mutual trust. and

Windows CE

Do not allow users to log in, when you must use

NTML Authentication

Time,

WMT

A dialog is popped up to obtain proof information.

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