Flow medium
With the development of the Internet, streaming media is getting more popular, flow media is audio, video or multimedia files transmitted through network, flow media do not download the entire file, streaming media before playback The flow is sent at any time, but there are some delays at the beginning. When the flow media file is transferred to your computer, some contents of the file have been stored in memory before playing. Currently, a popular streaming media technology is the RealNetwork's RealPlay product, many Internet musicians, and video on-demand sites using this product. Microsoft has introduced Windows Media technology in recent years, with its convenient, advanced nature, integration, low cost, etc., gradually be recognized.
Windows Media's predecessor is Microsoft's NetShow products, with the wide application of streaming, launched a complete set of streaming media production, publishing, and playing products, the server-end Windows Media Server products can be installed on Windows NT Ser Ver Pack 4, And integrated in Windows 2000 Server that is about to officially launched. A major feature of Window S Media products is that it is integrated with Windows NT / 2000 / 9X, and it is necessary to become mainstream products for future streaming applications.
Windows Media can be used for entertainment, training and online education:
1. Illustrate Audio: You can record the PowerPoint lecture to the CD or WE B site. If the user passes IE, you can see that a PPT will automatically flip. Working is: As long as the sound of the lecturer (tape or electronic format) and PPT files, Windows Media provides the Encoder tool to insert Mark ER in the sound, and then in the process of sound playback, these Marker The PPT picture will be turned to keep the sound and the PPT picture.
2. Streaming video: After obtaining the video signal with a camera or projector, you can perform Internet-based live live broadcasts through the web site; or save it as a .nsf file to play on demand. Need to install a normal video capture card and sound card on a higher configuration PC, then enter video through the video capture card and enter the sound signal through the sound card to live broadcast or recorded the medium.
3. Remote seminar: The instructor issued a notice in advance, and the audience accessed a URL address before the lecture. When the lecture started, the audience could see the speaker's image and heard his voice. There is also a PPT picture. When the speaker flips the PPT, the user's PPT picture is also automatically flipped. The whole lecture can also be recorded, and later on demand. It is necessary to use Multicast to pass the PowerPoint file to the IIS server in advance. When the listener is waiting for the lecture, the PPT image downloads to the user's browser Cache. Record the image and sound of the speaker with the camera, broadcast through real-time ENCODER. The live broadcast contains the PPT flip command, which allows the audience's browser to flip the PPT image in synchronization.
4. Provide a Pay By View: When the user needs to see the content supplier live or on demand content, if he has no license, Windows Media Player will take him to the content provider's website, come (pay Apply a license. The Digital Rights Management feature provided in Windows Media 4.0 can encrypt the content of the content provider to ensure that the information will be broadcast after the fee is charged. In addition, if you are a music enthusiast, Windows Media 4.0 also provides MS Audio CODEC compression technology, which provides the effect of providing FM radio for ordinary dial-up users. If the content is made into WMA (Windows Media Audio), the compression efficiency is doubled than MP3, and the user can play in Wince after downloading. The Internet radio has been implemented in IE 5, but also MS Audio.
Windows Media Technology
Microsoft Windows Media Service is a release platform that adapts to streaming multimedia information of a variety of network bandwidth conditions, including a complete set of solutions for streaming, publishing, playing, and management. In addition, it is also provided that the development kit (SDK) is used for secondary development.
The core of Windows Media Service is ASF (Advanced Stream Format). ASF is a data format, audio, video, image, and control command script, etc., through this format, transmitted in the form of network packets, and implements streaming multimedia content. Among them, the content transmitted on the network is called ASF Stream. ASF supports any compression / decompression encoding method, and can use any underlying network transport protocol, with great flexibility.
The WindowsMediaService system includes three parts: production, release, and play. As shown below:
1. Windows Media Tools
Windows Media Tools Computers are used for production and generation of ASF Stream. It includes a series of tools with Wi NDOWSMEDIA AUTHOR (from discrete images, sound file combinations ASF files), VIDTOASF, WAVETO ASF, Media Presenter for PowerPoint 97 (is a PowerP Oint plugin, making PowerPoint's demo can be released through ASF Stream technology), Media Encode R (real-time audio, video acquisition, real-time ASF stream). The ASF Stream generated by these tools can be stored as .asf files, the MEDIA Encoder can provide an ASF stream to the publishing server in real time, providing real-time multimedia information publishing services.
2. Windows Media Server
The Windows Media server provides network issuance services for ASF streaming media, including two basic service modules: UNICA StService and Station Service. Where Unicast provides customers with a single-to-point connection, the STA TION provides a broadcast service. The Unicast service can be divided into two types according to the user's participation. First, on-demand UN ICAST, in this way, the user builds and publishes the point-to-point connection of the publish server, which can control the process of playback, including start, pause, fast forward Wait. The other is Broadcast unicast. In this way, the user also establishes a point-to-point connection with the publishing server, but in a passive receiving state, can only watch playback, just as in broadcast service mode, this is generally used for real-time information release . 3. Windows Media client
The Windows Media client can be used independently, or conveniently embedded in the browser or other application in the form of ActiveX Control. It can play both the content provided by Unicast Service or play the broadcast content provided by Station Service. In addition, it also supports a variety of common multimedia file formats, such as AVI, QuickTime, MPEG, etc.
The Windows Media system also provides a set of management tools for the home page, which can easily remotely manage the server, complete server configuration, monitoring of various events, traffic, traffic, and logging of client access.
2.1 Working
The Windows Media Service system can be used in a variety of network environments, and basic applications have the following:
1. ON-Demand Unicast (on-demand service)
On-demand service work mode
Describe the mode of work of the on-demand service, this application is suitable for the on-demand service of multimedia information. Because the ASF technology supports any compression / decompression encoding, you can use any underlying network transmission protocol, allowing it to use both in a high-speed local area network, or in a low-bandwidth INTERNE T environment in a dial-up method, and The specific network environment is optimized. In the on-demand service mode, the user does not interfere with each other, and the playback of the on-demand content can be controlled, the most flexible, but the server, the network resources can be taken.
2. Broadcast Unicast / Multicast (single or more broadcast service)
Single or more broadcast service work mode
Describe the single or more broadcast service work mode, under the broadcast service, the user only views the content of the play, and does not control. You can use ASF files as the source of media content, but real-time multimedia content is best for broadcast service. Enter the camera, the content recorded by the video capture card into Media Encoder, and generate an ASF stream, then send it to MediaServer. In a network supported broadcast, you can use Station Service to save network bandwidth, reduce server load, in a network that does not support broadcast, you can use the Broadca St Unicast Service, and broadcast with Unicast.
3. Distribution (server extension)
Server extension work mode
The server extension work is described. The ASF stream output by a Media Server can be output to another Media Server through the Distribution mode. An application is that the distribution server can be expanded by Distributio N, for more user services. Another application, can provide broadcast services to non-broadcast networks through distribution. In addition, Windows Media Service also supports HTTP Stream modes, using a universal HTTP protocol, which can be better working on the Internet, such as transfers across the firewall for media content. Windows Media System Design
According to the requirements and applications, WINDOWS Media technology is used to facilitate design. The following uses Windows 2000 to design a set of distance education, and its network structure is shown in Figure 4.
Distance education network structure
1. Distance Education Center
The distance education center consists of tool computers, Windows2000 Media servers, and teachers. Tool computer Install video capture card, sound card, and camera for making streaming media files; Windows2000 Media servers are used to store and issue streaming media information; teacher machine can be placed elsewhere, other places of network or network, install video capture card, sound card Camera.
2. Student machine
The student machine uses Windows 9x or Windows 2000 Professional System, requiring IE browser, Office 97/2000, Windows Media Player software.
3. Internet connection
There are a variety of remote education networks:
(1) Campus Network
The campus network speed is faster, and the router that supports multi-point broadcast routing protocols, if there is no single broadcast.
(2) Internet
The Internet is slow, and the multi-broadcast protocol is not supported, and the function is restricted, but it can also be played. (3) Special data line
Through the dedicated data line connection, the speed is faster, try to choose a router that supports multi-point broadcast routing protocols.
(4) Telephone dial
The phone dial speed is slow.
4. Computer operating environment
(1) Windows Media Encoder Encoding Computer, Need: Windows 98 / Audio C Ard / VideoCaptureCard / MIC Phone / Video Camer.
(2) Windows Media server computer, WINDOWS MediaServices installed in Windows NT4 / SP4 or Windows 20 00.
(3) Windows Media customers, require Windows Media Player 6.4 software.
Conclusion Windows Media technology has a wide range of applications and can develop new applications on this basis. Although Windows Media supports the transfer speed of 20kb / s, it is often not required to reach the requirements. The currently feasible application environment is in Tranet (such as campus network, enterprise network, etc.), with the Internet speed will be obtained More common application.
Windows Media Player - ASF stream player Windows Media Player is an important part of the stream playback scheme proposed by Microsoft, is a universal media player. In the Media Service solution, Media Player is used as a client streaming application. In fact, Media Player can be used separately as a normal application, play stream information on a local or network; can also start to play stream information by super connections in the HTML text; it can also be used as an ActiveX object Used in the web page. Media Player acts as a universal media player except for streaming of ASF format, it can also play media information in a variety of formats, including: sound file (.wav, .snd, .aif, .au, .mp3) , MIDI file (.mid, .rim, .midi), image file (.mov, .avi, .qt .wmv, .mpg, .mpeg, M1V), playlist (.asx, .wax,. M3U), etc. Current Media Player is integrated in IE5.0 of Microsoft, if you want to use Media Player in Netscape or Low Version IE, you can install it, users can download for free on Microsoft www.windowsmedia.com. The work interface of Media Player is shown in Figure 1. Below we will introduce a detailed introduction to the use of Media Player. First we must simply introduce how to use Media Player as a separate application, and how to build HyperLink in HTML to launch Media Player. Then focus on how to use Media Player as an ActiveX object in the web page, and control it with JavaScript. MEDIA Player's work interface 1 Put the Media Player as a separate application as a separate application as a separate application, just select Open in the File menu, then enter or select the file you want to play, you can The file is played. as shown in picture 2. If you want to play the program broadcast on the Media Server, you can enter MMS: // ip_address / station_name to play the program on Server on the Open dialog box. Where IP_ADDRESS is the address of Media Server, and station_name is the station name of the program.
Play an ASF file directly with Media Player
2 Another way to use the ASX file in HTML to open Media Player to open Media Player is a super connection in HTML, which requires an ASX file to assist in completing this work. The ASX (Advanced Stream Redirector) is a text file that is mainly redirected. In the ASX file, the URL (Uniform Resource Locator) corresponding to the media content is included. When we let a HyperLink contact with the ASX in HTML, the browser will give the ASX content directly to Media Player, Media Player will be based on the ASX file. Information Use the corresponding protocol to open the multimedia information flow or multimedia files on the specified location.
The main reason for redirecting stream information using an ASX file is that currently general browsers do not directly support protocols for broadcast flow information, such as Microsoft's Media Server Protocol (MMS) or Microsoft? Netshow? Theater Server Protocol. The protocols they usually support are HTTP, FTP and other protocols. So if we link in the HTML file is http://www.microsoft.com, all browsers can be connected to a WWW server with an HTTP protocol. Conversely, if we need a Media Server to establish a connection to play stream information, you must use the MMS protocol, such as MMS: //202.112.107.59/station1, but because currently general browsers can usually support the MMS protocol, browser Can't establish a connection with Media Server. In order to solve this problem, an ASX file must be used. After using the ASX file, when the browser finds a connection to ASX, it knows that you need to use Media Player to play stream information, so it will automatically start Media Player, and send the information of the ASX file to Media Player, Media Player can Play the stream information with protocols such as MMS. The ASX file is a simple text file, we can use any text editor to edit the generated, but the extension must be .asx. An example of an ASX file is given below. demo </ title> <entry> <ref href = "mms: //202.112.107.59/demo/demo.asf" /> </ entry> </ asx> first The line is the version number, the second line is the title, some of the part of <entry> </ entry> Description Media Player Apply MMS protocol to play the network calculation 202.112.107.59 Demo.ASF files under the Demo path on the DEMO path. The ASX file can have information on its own title, author, copyright, which can have multiple, indicating that there are multiple streams to play, which is played, each <entry> <entry> < / entry> There is also a related information belonging to each stream including Title, Author, Copyright, etc. In the examples below, there are two programs to play, they have their own information. <Asx version = "3.0"> <title> Example Media Player Show </ title> <author> Windows Media Technologies </ Author> <Copyright> (C) 1999, Microsoft Corporation </ Copyright> <entry> <title> Example Clip </ title> <author> Windows Media Technologies </ author> <copyright> (c) 1999, Microsoft Corporation </ copyright> <ref href = "mms: //samples.microsoft.com/media.asf" /> </ Entry></p>
<p><Entry> <title> another clip </ title> <author> Windows Media Technologies </ author> <copyright> (c) 1999, Microsoft Corporation </ copyright> <ref href = "mms: //samples.microsoft.com /more_media.asf "/> </ entry> </ asx> The method of using the ASX file in HTML is very simple, the same as the way to create a normal HyperLink. Here is a simple HTML file Testasx.htm, which gives a link to the ASX file. <html> <head> <meta http-equiv = "content-type" content = "text / html; charSet = GB2312"> <title> test asx file </ title> </ head> <body> <p> < a href = "http://202.112.107.59/Broadcast/station.asx"> Test asx </a> </ p> </ body> </ html> is more simple in addition to the user yourself created an ASX file It is created by Media Server. When we want to play stream information with Media Server, we must set up the broadcast program stream, such as specifying stream file names, specifying play protocols. When the setting is completed, Media Server will automatically create an ASX file according to the user's settings, using the ASX file Media Player to play the program stream played by Media Server. We can use this ASX file to build a link with HTML without requiring users to write ASX files themselves. 3 Using Media Player in the web page Although the above two methods can complete the playback of stream information, the shortcomings are played in a separate window. For example, in HTML through the link with the ASX file, you can open and play flow information, but the playback of stream information is performed in another window, and the playback control needs to be done in the player window. Fortunately, Media Player is a standard ActiveX control, we can use it as an object to be embedded in the HTML page, so you can use the Player object directly to play flow programs directly in the web page. Figure 3 is an example of an embedding of a Player into a web page.</p>
<p>Figure 3 The method of embedding Media Player in a web page in a web page is relatively simple, as long as <object> </ Object> in HTML can be used, as shown below. <OBJECT ID = "WMPlay" WIDTH = 320 HEIGHT = 240 CLASSID = "CLSID: 22D6f312-B0F6-11D0-94AB-0080C74C7E95" CODEBASE = "http://activex.microsoft.com/activex/controls/mplayer/en/ nsmp2inf .cab # Version = 6, 4, 5, 715 "Standby =" Loading Microsoft? Windows Media? Player Components "Type =" Application / X-oleObject "> </ Object> where ID is the name of the object, when the user is JavaScript To control the name WmPlay of the object when controlling Media Player. CodeBase indicates that you can get from the URL specified when you have no Player controls in your user's browser. Of course, you can use <param> to specify parameters for <param> when establishing a Player object. As shown below: <param name = "filename" value = "c: asfrootwelcome.asf> <param name =" showcontrols "value =" false "> <parame =" autorewind "value =" true "> <param name = "AutoStart" value = "false"> where "FileName" parameters indicate the files or streams of Media Player to play. "ShowControls" indicates whether a control bar is displayed during playback. Madia Player has a lot of parameters, and we will not be detailed here. Readers If you need to know more detailed content, you can refer to the relevant part of the Media Player SDK. If the user needs to control the Media Player to be controlled with JavaScript. Figure 4 shows an example of controlling Media Player with JavaScript. Figure 4 Controlling the MEDIA Player with JavaScript In this example, Media Player is embedded in the web page, with some buttons on the right side of Media Player, using these buttons users to control the Media Player's playback activity.</p>
<p>The HTML code of these buttons is as follows: <form name = "myform"> <input type = "button" width = "15" value = "no controls" name = "nocontrols" onclick = "ControlType (false)> <input type = "Button" width = "15" value = "all controls" name = "overclick =" limited "> <input type =" button "width =" 15 "value =" small "name =" small "Onclick =" DisplaySize (1)> <input type = "value =" large "name =" onclick = "displaysize (2)> <input type =" button "width =" 15 "value = "Normal" Name = "Normal" OnClick = "DisplaySIZE (0)> <input type =" butt "width =" 15 "value =" play "name =" onclick = "PlayClick ()> <input type = "Button" width = "15" value = "stop" name = "stop" onclick = "stopClick ()> </ form> The corresponding JavaScript code is: <script language =" javascript "> <! - var g_Browser = navigator.appName; function controlType (setting) {if (g_Browser == "Netscape" document.WMPlay.SetShowControls (setting); else document.WMPlay.ShowControls = setting;} function displaySize (setting) {if (g_Browser == "Netscape" Document.wmPlay.SetDisplaysize (Setting); ELSE Document.wmplay.displaysize = setting;} function playclick () {document.wmplay.play ();} function stopClick () {document.wmplay.stop (); if (g_browser == "Netscape"</p>
<p>document.WMPlay.SetCurrentPosition (0); else document.WMPlay.CurrentPosition = 0;} function PauseClick () {document.WMPlay.Pause ();} function PlayPauseClick () {var state; if (g_Browser == "Netscape" state = Document.wmPlay.getPlayState (); else state = document.wmplay.PlayState; if (state == 0) Document.wmplay.Play (); else if (state == 1) Document.wmplay.play (); Else IF (state == 2) Document.wmplay.pause ();} // -> </ script> From this example, it can be seen when a button is one of them, and its corresponding onclick function will be called In the JavaScript function, you can directly control the activity of the player directly, such as start playing, stop playing, or occupying the playback, and zooming, except for an action such as a mouse to control the embedded Media Player. You can also use events to control it. Microsoft? Windows Media? Player supports a lot of events, there are ordinary mouse events, such as clicking, double-click, mouse movement, mouse keys, and release, etc. There are also some incidents with the MEDIA Player. Events with direct relationships are: OpenStateChange, PlayStateChange, Buffering, Markerhit, ScriptCommand et al. We will briefly introduce these important events.</p>
<p>1 OpenStateChange Event OpenStateChange event indicates that the status of Player has changed. The open state of Media Player is: 0 indicates that the stream has been closed (NSCLOSED) 1 indicating that the ASX file (NSLoadingAsx) 2 indicates that the NSC file (NSLoadingNSC) 3 indicates that the Media Server (NSLocating) 4 indicates that is being with Media Server Establishing a connection (nsconnecting) 5 indicates that the flow information is being opened or listened to the flow information. The format of the OpenStateChange event is processed by the stream information has been opened (NSOpen). ) "Language =" jscript "> // INSERT Script commands // </ script> where MediaPlayer is the name when the Media Player object defined in <object> </ Object>.</p>
<p>2 PlayStateChange event PlayStateChange event indicates that the playback status of Media Player has changed, and Media Player may be: 0 Play has stopped (MPSTOPPED) 1 Playing pause (MPPASED) 2 is playing (MPPLAYING) 3 is waiting to start (MPWAITING) 4 Front Search (MPScanForward) 6 Backward Search (MPSkipForward) 7 Backward Jumping (MPSkipReverse) 8 stream Has been closed (MPCLOSED) The method of processing the event with JavaScript: <script for = "MediaPlayer" Event = "PlayStateChange (LNEWSTATAT" "Language =" jscript "> // INSERT Script Commands // </ script> 3 BUFFERING Event Buffering event means that Media Player is buffering data is ready to play. Before performing flow playback, Media Player must buffer a certain number of data before starting playback, the buffering event reflects the status of Player buffer data. The method of processing the buffering event with JavaScript is: <script for = "MediaPlayer" Event = "Buffering (bstart)" Language = "jscript"> // insert script commands // </ script> where bstart is a Boolean variable, when it When the buffer is being processed, it means that the buffer has ended.</p>
<p>4 ScriptCommand Event ScriptCommand event indicates that the Media Player has received the script command. At this time, the user can analyze the receiving Script command to determine the corresponding processing. We know that the ASF INDEXER tool that uses Media Tools can add the script command. When the stream player Player receives these script commands, this event processing method is activated, so the user can process the script command in the event processing method. The method of processing ScriptCommand is: <script for = "MediaPlayer" Event = "scriptcommand (stype, spram)" Language = "jscript"> // INSERT Script commands // </ script> where Stype is the type of script command, script command Types include URL, Text, Event, etc., users can do different processing depending on the Script command type. For example, if it is a URL command, we can open the page specified in the spram within the specified frame.</p>
<p>5 MarkHit Event Markerhit Events The same ScritpCommand event, when the media player encounters tags in the ASF stream, users can use this event to know that the current tag is the first tag. MARKERHIT event is: <script for = "MediaPlayer" Event = "markerhit (lmarkernum)" Language = "jscript"> // insert script commands // </ script> Of course, in addition to supporting event processing, An ActiveX object, MEDIA Player has a lot of properties and methods (Method) available for web page. For example, use the MediaPlayer.Markercount property you can know how many tags in the ASF stream; use the MediaPositioner. The currentPosition property can know the time of the current play position, etc. As for the method of Media Player, we have used a lot in front, such as Play (), and pause (), etc. are MEDIA Player methods. Due to the attributes and methods of the Media Player object, we cannot introduce this one by one, but only a certain introduction to several more important event processing. Users can refer to the help document for the Media Player SDK when they are used to get more information. This article uses the use of Media Service's client application Media Player, especially in the web page. As a universal media player, there are still many features that have not been introduced here. To understand the function of a software, the best way is to use it. If you are interested, you can download the free download from www.windowsmedia.com This article describes the features, features, and composition of Windows Media technology, which shows how to use Windows Media for application design (such as design distance education). The application of streaming media is the product of Internet development in recent years. It is widely used in distance education, network radio, video on demand, fees, etc., Microsoft's Windows Media technology has been bundled in Windows 2000, will be generated to the Internet Important impact, INTERNT / INTRANET will no longer be simple text and images, sounds and videos will become the focus of future networks. With the development of the Internet, streaming media is getting more popular, flow media is audio, video or multimedia files transmitted through network, flow media do not download the entire file, streaming media before playback The flow is sent at any time, but there are some delays at the beginning. When the flow media file is transferred to your computer, some contents of the file have been stored in memory before playing.</p>
<p>Currently, a popular streaming media technology is the RealNetwork's RealPlay product, many Internet musicians, and video on-demand sites using this product. Microsoft has introduced Windows Media technology in recent years, with its convenient, advanced nature, integration, low cost, etc., gradually be recognized.</p>
<p>Windows Media's predecessor is Microsoft's NetShow products, with the wide application of streaming, launched a complete set of streaming media production, publishing, and playing products, the server-end Windows Media Server products can be installed on Windows NT Server Pack 4, and Integrated in Windows 2000 Server, which is about to officially launched. A major feature of Windows Media products is its production, publishing, and playback software integrated with Windows NT / 2000 / 9X, do not need additional purchase, will become mainstream products for future streaming applications. Windows Media can be used for entertainment, training and online education:</p>
<p>(1) Illustrate Audio: You can record the PowerPoint lecture to the CD or Web site. If the user passes IE, you can see that a PPT will automatically flip at the same time. Working is: As long as the sound (tape or electronic format can be provided) and PPT files, Windows Media provides the Encoder tool to insert Marker in the sound, then in the process of sound play, these Marker will Turning the PPT image to keep the sound and the PPT picture synchronize.</p>
<p>(2) streaming video: After obtaining the video signal with a camera or projector, you can perform Internet-based live live broadcasts through the web site; or save it to the .nsf file to play on demand. Need to install a normal video capture card and sound card on a higher configuration PC, then enter video through the video capture card and enter the sound signal through the sound card to live broadcast or recorded the medium.</p>
<p>(3) Remote seminar: The instructor sent a notice in the Internet / Intranet, and the listener visited a URL address before the lecture started. When the lecture started, the audience can see the speaker's image and hear him. Sound, there is a PPT picture. When the speaker flips the PPT, the user's PPT picture is also automatically flipped. The whole lecture can also be recorded, and later on demand. It is necessary to use Multicast to pass the PowerPoint file to the IIS server in advance. When the listener is waiting for the lecture, the PPT image downloads to the user's browser Cache. Record the image and sound of the speaker with the camera, broadcast through real-time ENCODER. The live broadcast contains the PPT flip command, which allows the audience's browser to flip the PPT image in synchronization.</p>
<p>(4) Pay by View: When the user needs to see content supplier live or on demand content, if he has no license, Windows Media Player will take him to the content provider's website, come ( Pay) Application License. The Digital Rights Management feature provided in Windows Media 4.0 can encrypt the content of the content provider to ensure that the information will be broadcast after the fee is charged. Windows Media 4.0 also provides MS Audio Codec compression technology that provides the effect of fuel-frequency sounding for ordinary dial-up users. If the content is made into WMA (Windows Media Audio), the compression efficiency is doubled than MP3, and the user can play in Wince after downloading. The Internet radio has been implemented in IE 5, but also MS Audio.</p>
<p>2 Windows Media Technology Microsoft Windows Media Service is a release platform that can accommodate flow multimedia information of a variety of network bandwidth conditions, including a complete set of solutions for streaming, publishing, playing, and management. In addition, it is also provided that the development kit (SDK) is used for secondary development. The core of Windows Media Service is ASF (Advanced Stream Format). ASF is a data format, audio, video, image, and control command script, etc., through this format, transmitted in the form of network packets, and implements streaming multimedia content. Among them, the content transmitted on the network is called ASF Stream. ASF supports any compression / decompression encoding method, and can use any underlying network transport protocol, with great flexibility. The WindowsMediaService system includes three parts: production, release, and play, as shown in Figure 1. Windows Media application system structure</p>
<p>1. Windows Media Server Windows Media Server provides network publishing services for ASF streaming media, including two basic service modules: UNICAST Service and Station Service. Where Unicast provides customers with a service of point-to-point connection, STATION provides a broadcast service. The Unicast service can be divided into two, one is ON-Demand Unicast, in which mode, the user builds and publishes the point-to-point connection to the server, which can control the process of playback, including start, pause, fast forward, etc. . The other is Broadcast unicast. In this way, the user also establishes a point-to-point connection with the publishing server, but in a passive receiving state, can only watch playback, just as in broadcast service mode, this is generally used for real-time information release . The Windows Media system also provides a set of management tools for the home page (Figure 2) that can be easily managed to remotely manage, complete server configuration, monitoring of various events, traffic, and logging of access to clients.</p>
<p>WINDOWS Media Manager</p>
<p>2. Windows Media Tools The Windows Media Tool computer is used for the production and generation of ASF Stream. It includes a series of tools with Windows Media Author (from discrete images, sound file combinations ASF files), VIDTOASF, WAVETOASF, Media Presener for PowerPoint 97 (is a PowerPoint plugin, making PowerPoint Demonstration can be released through ASF Stream technology), Media Encoder (real-time audio, video capture, generating real-time ASF stream, as shown in Figure 3). The ASF Stream generated by these tools can be stored as .asf files, the MEDIA Encoder can provide an ASF stream to the publishing server in real time, providing real-time multimedia information publishing services.</p>
<p>Windows Media Encoder</p>
<p>3. The Windows Media client Windows Media client can be used independently, or it can be easily embedded in the browser or other application in the form of ActiveX Control. It can play both the content provided by Unicast Service or play the broadcast content provided by Station Service. In addition, it also supports a variety of common multimedia file formats, such as AVI, QuickTime, MPEG, etc. Windows Media Player</p>
<p>Windows Media services can also be installed on the Windows NT ServerPack 4 platform, and server software, tool software is free, users can download by www.microsoft.com/windowsmeida. Bundled Windows Media software in Windows 2000, but there is no software in Windows 2000 B3, which can be seen in the version after Windows 2000 RC2, and its client playing software comes with Windows 98, Windows 2000 Professional. It is "Windows Media Player" under the "Entertainment" (Figure 4).</p>
<p>2.1 Working Working Windows Media Service System can be used in a variety of network environments, basic applications have the following:</p>
<p>1. ON-DEMAND UNICAST This application is suitable for multi-media information. Because ASF technology supports any compression / decompression encoding, you can use any underlying network transport protocol, allowing it to use both in a high-speed local area network, or in a low-bandwidth Internet environment in dial-up mode, and for specific The network environment is optimized. In the on-demand service mode, the user does not interfere with each other, and the playback of the on-demand content can be controlled, the most flexible, but the server, the network resources can be taken.</p>
<p>2. Under the Broadcast Unicast / Multicast broadcast service, users only view the contents of the playback and do not control. You can use ASF files as the source of media content, but real-time multimedia content is best for broadcast service. Enter the camera and microphone record through the video capture card to Media Encoder, and generate an ASF stream, then send it to Media Server. In the network that supports the broadcast, you can use Station Service to save network bandwidth, reduce server load, in a network that does not support broadcast, you can use the Broadcast Unicast Service, and use unicast to implement broadcast.</p>
<p>3. Distribution (Server Extension) You can output an ASF stream output from a Media Server to another MEDIA Server to provide services to users by DISTRIBUTION. An application is that the release server can be expanded through Distribution, for more user services. Another application, can provide broadcast services through the Distribution to the Non-broadcasting network. In addition, Windows Media Service also supports HTTP Stream modes, using a universal HTTP protocol, which can be better working on the Internet, such as transfers across the firewall for media content.</p>
<p>3 Software and hardware requirements for a Windows Media system</p>
<p>1. The server can set one or more servers according to the situation, and the server hardware configuration is generally Piii400 or more CPUs, and there is from about 128 to 512m. Software Install Windows 2000 Server and Windows Media services. If there are more content content, you can put the ASF file on one server. If it is a wide area network (or more users), a server can be set up at each local area network, and the ASF stream is output by the center server, and then output to another Media Server, and provide services to the user. 2. Making computer production computer hardware configuration is typically Piii400 or more CPUs, including 218 ~ 512m, requires sound card (forget to be about a few hundred yuan), video capture card (about 1,000 yuan), and VCD or video recorders. Software is Windows 98 or Windows 2000 Professional, installing Windows Media Editing tools.</p>
<p>3. The customer's computer customer computer is a general Windows 95/98/2000 computer, a soundup card, which requires Windows Media Player software.</p>
<p>4. Network equipment network bandwidth required in 20K (dial-up) to 2M, the general local area network can, if desired multicast mode, the router must support multicast protocol Author: Zhao Hang</p></div><div class="text-center mt-3 text-grey">
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