Microsoft® NetShow 2.0 is a platform for streaming multimedia over networks that range from low bandwidth dial-up Internet connections to high bandwidth switched local area networks. Using NetShow, companies can offer new streaming content for applications such as training, corporate communications, entertainment, and advertising to users all over the world. NetShow is a powerful broadcast system that is easy to acquire and operate, and that empowers companies to offer rich, high-quality interactive content over today’s networks.

Only a few years ago, the business world was full of text documents, and adding graphics to them was not easy. Now the race is on to offer Web sites that attract and retain visitors through the latest in graphics and animation. Audio- and video-enabled Web sites and applications are the next wave. The integration of audio and video into applications such as online training, corporate communications, customer and sales support, news and entertainment services, and product promotions will provide individuals and organizations with new and exciting ways to communicate.

Microsoft NetShow provides a complete platform for integrating audio and video into online applications, bringing the vibrant power of networked multimedia to the Internet and corporate intranets. With its leading-edge live and on-demand media-streaming technology, Microsoft NetShow allows users to receive audio and video broadcasts from their personal computers. It uses a client/server architecture and sophisticated compression and buffering techniques to deliver live and on-demand audio, video, and illustrated audio (synchronized sound and still images) to users of the NetShow player. The NetShow player continuously decompresses and plays the content in real time. Users can listen and watch live audio and video programs or navigate on-demand audio and video content.

Building on the open, standards-based platform established with NetShow 1.0 networked multimedia software, NetShow 2.0 provides an easy, powerful way to stream multimedia content across the Internet and intranets. NetShow 2.0 allows developers and Web professionals to add production-scale audio and video broadcasts to any Web application or site.

Microsoft NetShow 2.0 delivers the following:

• Powerful broadcast system. NetShow 2.0 delivers a complete, high-performance system for broadcasting live and on-demand audio, video, and multimedia.
• Ease of use and reduced cost of ownership. NetShow 2.0 reduces the total cost of streaming multimedia because of its tight integration with Microsoft Internet Information Server, Microsoft Windows NTÒ Server network operating system, and the Internet Explorer browser. Standard multimedia authoring and HTML programming tools can be used to create and host content.
• High-quality audio and video over the Internet. NetShow 2.0 enables high-quality content generation and streaming with new, next-generation compression/decompression (codec) technology. Using great compression technology from a variety of companies, including Voxware and Fraunhofer Institut Integrierte Schaltungen (FhG), Microsoft, and Vivo Software, NetShow delivers the best range of codecs for creating content that suits a particular application and bandwidth.
• Rich, synchronized multimedia experience. NetShow 2.0 enables live and on-demand streaming of audio, illustrated audio, and video synchronized with pictures (JPEG, BMP, and GIF files) as well as script (Jscript™ and ActiveX™ script), URLs, and text. The result is a compelling mixed-media experience, and the ability to deliver multimedia applications over low bandwidth networks like the Internet.

NetShow, with its authoring tools, client and server APIs, and ASF file format, represents a significant source of opportunity for third parties creating value-added products such as NetShow authoring tools, streaming media servers targeted toward vertical markets, and multimedia tools. Independent software developers can augment their own products with NetShow functionality or provide compatible add-ons.

NetShow joins the NetMeeting™ conferencing software in the Microsoft family of networked multimedia products. Together, they provide complete information-sharing solutions, spanning the spectrum from one-to-one, fully interactive meetings, to broadly distributed one-way, live or stored presentations. While NetMeeting enables one to communicate with a small number of others, such as for desktop videoconferencing, NetShow makes it possible to reach a virtually unlimited audience.

Microsoft NetShow 2.0 is also in the same product family as the Microsoft NetShow Professional Video Server, which provides a powerful way to deliver high quality MPEG video across high bandwidth corporate networks and dedicated video LANs. Typical uses for the Microsoft NetShow Professional Video Server are to provide rich interactive multimedia on networks that can accommodate high-bandwidth traffic, such as switched networks, dedicated training local area networks, or networked kiosk systems. Key markets for the Microsoft NetShow Professional Video Server are entertainment, training, advertising and retailing, and hospitality, for use in hotels, cruise ships, and in-flight entertainment systems.

Together, Microsoft NetShow and Microsoft NetShow Professional Video Server enable a full range of audio and video delivery solutions over a variety of networks.

NetShow provides a wide variety of features that allow customization of the system. How you use NetShow depends largely on the types of media you want to stream and the characteristics of the network used to deliver the data. Understanding these basic concepts helps determine how to deploy NetShow for your particular application.

• How NetShow works: media streaming. Most of the audio and video content currently hosted on intranets and on Internet sites is downloadable. This means that the multimedia content must be copied to the user's local PC before it can be played. NetShow uses a client/server streaming architecture to deliver multimedia content to clients. Streaming content is digitized content that has been compressed or encoded into a format that the server can break down into packets and then stream across a network to a client player. Streaming is a significant improvement over the download-and-play approach to multimedia file distribution because it allows content to be delivered to the client as a continuous flow of data with little waiting time before playback begins. The content arrives, is buffered briefly, plays, and is discarded. It is never actually stored on the user's computer. NetShow users benefit by experiencing instant play, and don't have the frustration of waiting for content to download to determine whether it meets their needs or interests.

• Network bandwidth. Any computer network connection (Internet or intranet) has an upper limit on the amount of data that can pass through it in a given second. This data limit is called its bandwidth. The data rate (also bit rate) of a audio and video file is the amount of data that must transmit in a given second for the whole file to be heard or viewed in its entirety. To transmit a content file completely and smoothly, its data rate must be less than the available bandwidth of its target network.
• Content compression. Because today’s networks are usually bandwidth-constrained, audio and video files must be compressed to reduce their data rates. To compress, we apply mathematical compression algorithms called codecs that analyze the audio and video and decide what bits of data can be removed or merged with minimum impact on what the human ear will hear or eye will see. By nature, however, applying compression to an audio or video clip will result in some loss of quality.

The level of quality and fidelity you can deliver in sound and video files depends primarily on how much bandwidth you have available, and whether you have authored the content appropriately for that available bandwidth. For example, you can imagine that the bandwidth available is like an empty pipe. You decide to fill that pipe with audio only. If your pipe is large (that is, you are on a corporate network), you can author that audio to be only slightly compressed, so of very high quality. If your pipe is small (you are targeting users on 28.8 kbps dial-up connections), you will have to use a codec to compress the audio to fit in such a small pipe. It will sound worse than the audio authored for higher bandwidths. Now, imagine that you want to add images or video to that audio content. In order to make room in that pipe, you will need to compress the audio even more. You will also need to compress the images or video significantly. The end result will be highly compressed multimedia that can play at bandwidths that could support only still images.

Codec independence. The quality of content you end up with is largely determined by how good the codec is that you used to compress it. Advances in codec technology are happening practically monthly, and that’s why we’ve created NetShow to be codec independent. This means that we ship a variety of codecs with the product so you can choose which one to create content with, and your users can decode without hassles. Most other streaming media companies today use a proprietary codec (one that can be used only by that particular application, and other codecs cannot be used). Microsoft NetShow offers the content author and end user a well-rounded suite of bundled and stand-alone third-party codecs for voice, music, images, and video, at a variety of bit rates. This gives you more options, more flexibility, higher-quality content, and faster innovation, because the codecs can be upgraded independent of NetShow.

• Two key delivery techniques: unicast and multicast. Unicast refers to networking in which computers establish two-way, point-to-point connections. Most network operations today work in this fashion—a user requests a file, a server sends the file to that client only. When streaming multimedia over a network, the advantage to unicast is that the client computer can communicate with the computer supplying the multimedia stream. With Microsoft NetShow, for example, the NetShow server can provide a unicast video stream to a client, and the client can take advantage of the VCR controls in the NetShow player to ask the server to pause the stream or to skip backward or forward to a marker in the stream. The disadvantage to unicast is that each client that connects to the server receives a separate stream, which rapidly uses up network bandwidth.

IP Multicast refers to networking in which one computer sends a single copy of the data over the network and many computers receive that data. Unlike a broadcast, routers can control where a multicast travels on the network. When streaming multimedia over the network, the advantage to multicasting is that only a single copy of the data is sent across the network, which preserves network bandwidth. In large companies the bandwidth savings can be substantial. The disadvantage to multicasting is that it is connectionless; clients have no control over the streams they receive, so cannot pause or skip backward or forward in the stream.

To use IP multicasting on a network, the network routers must support the IP Multicast protocol. However, whether or not your network routers support multicasts, you can always use NetShow multicasting on the local node of your LAN. In addition, by setting up NetShow servers on each node of your network, you can distribute a single stream to the NetShow server on each node and then use NetShow Server to multicast to clients on that node. Most routers sold within the last 2 to 3 years are able to handle multicast. In order to multicast-enable them, router software upgrades are required.

NetShow combines the best of these two delivery techniques, enabling network managers to choose whether unicast or multicast is most appropriate for their network and best suited for their applications and needs.

• Active Streaming format (ASF). The foundation for all of the components of NetShow content creation is the Active Streaming format (ASF). ASF is an open, standards-based file format that prepares multimedia content for streaming, and is the key format for the future, eventually replacing data types such as WAV and AVI. ASF adds error correction and other features necessary for streaming and content delivery over lossy networks. ASF also enables the synchronization of different data types on a common time line, enabling, for example, JPEG images, bitmaps, or WAV files to be synchronized with each other. Multimedia content must be converted to ASF before delivery over a network. ASF content can be hosted on a local hard drive, on an HTTP server, or on a specialized media server such as NetShow. This provides an extraordinary flexibility to the content creator: the same content can be played locally from a CD-ROM or a hard drive, or it can be played from a remote location hosted on an HTTP server or a specialized media server.

• NetShow channels. When you multicast multimedia or files using Microsoft NetShow 2.0, you first set up a channel. The channel establishes the communication between the server and the multicast clients. Much like a television channel, when users connect to a NetShow channel via the NetShow player or a Web page that embeds the feed in it, they get whatever is being played at the time. For example, you could tune into a particular channel and get nothing if there are no NetShow programs being played at the time.
• NetShow programs. When you multicast multimedia or files using Microsoft NetShow 2.0, you first set up a channel, then you populate that channel with programs, which are the content for that channel. Programs can be live feeds or on-demand content scheduled to be played at specific times. Much like television, what you see on your screen could be live, or it could be played from a tape at a specific time. Also like television, you can’t skip ahead or back; you get the broadcast and if you don’t like it you either turn it off or change channels.

Multimedia allows people to communicate better. The richer data structures of sound and moving images transcend the communicative power of text and graphics. This is why audio and video-enabled applications are the next wave of Internet-based technology. And this is why NetShow provides the complete platform for integrating audio and video into Web-based applications to deliver entertainment, training, corporate communications, and advertising.

• Training. Many organizations devote substantial resources to training. Using NetShow to extend the reach of professional instructors through corporate intranets lets organizations maximize the value of this investment. NetShow makes it easy for trainers to generate the content, and for users to receive the training whenever and wherever they need it. For example, a recorded speech in conjunction with the speaker's slides can form a NetShow broadcast. The training material can thus be provided for all divisions and subsidiaries of a corporation, so that all employees have the advantage of hearing the speech as it was delivered from the speaker. Likewise, being able to deliver multimedia information and presentations over corporate networks and the Internet can help companies save substantially on the costs formerly required to distribute training materials and binders or CD-ROMs. Also, since those hard copy materials can quickly become out of date, being able to update NetShow content immediately on the network can save money and provide more up-to-date information.
• Corporate communications. Everyone in an organization, regardless of their geographic location, can hear important organizational briefings live, such as internal presentations or presentations for the press or analysts. These same presentations can also be captured for later playback. This allows people to view presentations at their convenience, and can also grow into a library of available on-demand information for reference and training. NetShow can reduce the burden of having to have all employees fly into a central location for an announcement or training session by allowing companies to send the content over the network to each employee's desktop or to a portable PC for those traveling.
• Entertainment and information. NetShow makes Web sites come alive with interactive audio and video content, from musical events and similar entertainment to news and other broadcasts. Companies that already provide entertainment content on the Web can use NetShow to add visual content to their sites. When combined with products like Microsoft Site Server Enterprise Edition, companies can offer NetShow-based entertainment content for fun, and help justify its use by selling products over the Web using the Site Server.
• Advertising and retailing. Advertising a product or a service with audio and video can be much more compelling than doing it using only static Web pages. For example, audio commentary can be used with images on a Web site to guide users through demonstrations of a product, a process, or the site itself. The synchronized sound and images of NetShow illustrated audio provide a rich environment for advertising, and facilitate showing off a product or concept to best advantage, such as in a media catalog. Firms with external Web sites can promote and sell products on the Web using NetShow. This approach allows advertisers to use NetShow’s streaming to deliver their messages without having the users have to wait for a movie or audio clip to download to their hard disks, which means the users get the messages without the frustrating delay.

NetShow is a comprehensive, tightly integrated platform consisting of the following software components:

• NetShow Player. The NetShow player allows intranet and Internet surfers to play audio, illustrated audio (synchronized sound and still images), and full-motion video files. By simply activating a link to a file, the player launches automatically and begins playing the requested file. Within seconds, the content starts playing, with no download required. The player enables the same functions as a regular VCR, allowing the user to stop, pause, and start content. The NetShow player is an ActiveX control and a helper application that embeds the NetShow ActiveX control in it. The ActiveX control allows developers to embed NetShow content in applications that support ActiveX controls (like Internet Explorer, Visual BasicÒ , Visual C++Ò , and many third-party tools and applications). The NetShow player can be run independently of the user’s browser by launching it in a helper application that runs on top of the page. The advantage of playing content in the external player is that it can be launched via a small redirector in an e-mail message, launched from a shortcut to a location on a corporate network, or can play in the background while the user surfs to other pages on the Web.
• NetShow Server. The NetShow server consists of a set of services running on Windows NT Server 4.0 that allow you to unicast and multicast audio, video, and other files to client computers. The NetShow server can deliver both live and on-demand content. To deliver live, real-time content, the server works in conjunction with the NetShow Real-Time Encoder, which compresses the audio and/or video feed in real time and passes it to the NetShow server for delivery to the network. Delivery of on-demand content requires that it be stored on a server’s hard drive and passed to the network by the NetShow server. The server also includes the NetShow Administrator, a set of administrative tools to manage, configure, and monitor NetShow services. The NetShow server allows the server administrator to set the maximum number of concurrent streams the server can run and can limit the amount of data the server can send at one time. The NetShow server also allows you to configure and set up channels and programs that allow you to multicast content at specific times.

• NetShow content authoring and production tools. The foundation for the NetShow content creation components is the Active Streaming format (ASF). NetShow handles both real-time (live) and on-demand (stored) content:

Authoring of on-demand content. NetShow provides simple ASF authoring tools to convert AVI and QuickTime files to ASF or WAV files. Also provided is a simple ASF editor called the NetShow ASF Editor, which allows you to synchronize images to WAV audio files, and add URL flip commands, markers, and script events. Work is also underway to allow third parties to support ASF features natively within their products.

Encoding live content. NetShow provides a set of tools to encode and author live multimedia streams. These tools allow content authors to encode live audio and video feeds and add them to dynamic mixtures of other media, such as audio, video, text, URLs, and script commands. These tools are used to indicate when and what media is to be injected into a live stream. The appropriate media components are synchronized, compressed, augmented with error-correction information, and transmitted over a network.

• NetShow Software Development Kits (SDKs). NetShow comes with Software Development Kits for each of the three major components:

Client Software Development Kit. The Client SDK documents the interfaces to the player. This gives developers of Web pages and client applications all the information they need to integrate NetShow functionality into their products. The developer has complete control over audio and video rendering along with the ability to interpret script commands transmitted as part of the NetShow stream.

Server Software Development Kit. The Server SDK documents the interfaces to the three administration controls. This gives an application author complete local or remote control over a network of NetShow servers. As an example, NetShow administration could be integrated into an overall enterprise management system.

Real-Time Encoder Software Development Kit. The Real-Time Encoder SDK documents the interfaces to the Real-Time Encoder itself. This gives application developers the ability to automatically insert script commands into the NetShow stream alongside audio and video. For example, a closed caption or subtitling application could feed its output directly to the NetShow Real-Time Encoder by using these interfaces. The PowerPointÒ NetShow Presenter add-in for the PowerPoint '97 presentation graphics program is another example of an application written using the Real-Time Encoder SDK.

A number of major themes drive the feature set of NetShow 2.0. NetShow 1.0 delivered basic audio and video services, enabled multicast and unicast delivery of live and on-demand content, and provided the essential interfaces for codec vendors, tools vendors, and Web masters to build value-added software for NetShow. The key themes driving the functionality of NetShow 2.0 focus on extending the strengths of NetShow 1.0 to provide an open, standards-based system that customers can use for production deployments of audio and video broadcasts. Below are the themes guiding NetShow 2.0:

• Scale and distribution of the broadcast infrastructure. Broadcasts of audio and video on the Web need a server that can scale up to thousands of streams for enabling full-scale, one-to-many communication. The NetShow Server takes advantage of the scalability of Windows NT Server to provide a powerful and robust system that can maximize the power of microprocessors such as Intel Corporation's Pentium and Pentium Pro, and Digital Equipment Corporation's Alpha. It scales to very high-performance, enterprise-class multiprocessor systems with gigabytes of memory and terabytes of storage.

In addition, NetShow 2.0 supports even larger scale deployments by distributing the server software across multiple physical computers. While with NetShow 1.0 all of the server components were installed on a single Windows NT Server 4.0, NetShow 2.0 allows the system to be divided into several components that can be installed on separate Windows NT Server computers. This increases the overall number of simultaneous streams that can be delivered, and optimizes the server infrastructure needed for distributing content to clients. Using Windows NT Server DNS, it is possible to build a cluster of NetShow servers configured to deliver content to a greater number of clients. For example, if broadcasting a live event, the real-time encoding could be performed at the event site using a NetShow Real-Time Encoder. The encoded content is transmitted in real time to a cluster of NetShow servers that then deliver the content to their respective connected clients.

• Improved management of Web broadcasts. NetShow 2.0 is administered through an intuitive Web-based interface, which enables both local and remote administration of NetShow servers. This lets administrators manage server installations and make configuration changes without having to physically access each server. Network managers can set the maximum content throughput per file and per server to control network bandwidth utilization, and to monitor the state of all key NetShow server services. Server performance and event monitoring is achieved through close integration with the award-winning Windows NT Server administration system.
  In addition, NetShow 2.0 allows configuring and scheduling of content streams for later delivery, and supports the generation of basic announcements for notifying users of upcoming (or in-progress) sessions. This new functionality allows audio and video content to be organized into separate channels, each programmed with one or more individual programs. This opens up vast opportunities for Web-based broadcasts similar to the delivery of content over current television and radio stations.

• Delivery of live broadcast. NetShow 2.0 enables the delivery of live, real-time encoded audio, video, and illustrated audio content. This represents a major improvement, as NetShow 1.0 allowed live delivery of audio only over multicast-enabled networks, thus limiting the delivery of live events. In addition, NetShow 2.0 allows the delivery of live content, as well as on-demand content, over any network, independent of the transmission techniques and network transports used. This means that people using NetShow can broadcast live and on-demand content using either unicast or multicast techniques, depending on their needs and the available network infrastructure. To further facilitate delivery, NetShow can automatically switch from multicast to unicast to accommodate networks that are not multicast-enabled, or to adjust to other delivery needs.

• Easy user access to audio and video broadcasts on the Internet and corporate intranets. NetShow brings the power of broadcasting to Microsoft Internet Explorer, enabling it to receive a new class of innovative interactive content and extending its strength for one-to-many communication. Because the NetShow 2.0 client is an integral part of Internet Explorer 4.0, users can easily view NetShow-hosted broadcasts. NetShow 2.0 also includes a Netscape Navigator™ Plug-in, enabling users of this browser to receive NetShow broadcast directly within their browsers. And NetShow 2.0 provides a stand-alone player that is capable of receiving audio, video, images, and URLs. This stand-alone player is useful when there is no browser present to host the embeddable NetShow player. Stand-alone players are also available cross-platform, providing users of Mac, UNIX, Windows 3.1, and Windows NT 3.51 users access to NetShow content.

NetShow 2.0, with its tight integration with Windows NT, Microsoft Internet Information Server, and Microsoft Internet Explorer, and with its support of open industry standards, provides a wealth of benefits and features for developers, Web professionals, network managers, and other users. Below are the features and benefits of each component of the product.

Tightly integrated with Windows NT Server and IIS. NetShow and its streaming services are tightly integrated with Windows NT Server to provide an efficient, reliable, scalable, and secure platform for delivering audio, illustrated audio, and video content over corporate intranets and the Internet. NetShow utilizes all key Microsoft Windows NT Server manageability features, including a graphical administration console, performance monitoring, an integrated directory and security model, and the Event Log, which records program execution information. NetShow also fully supports Windows NT connectivity, including network environments such as IP, IPX, 14.4/28.8 POTS, ISDN, Ethernet, and others. Sharing the same user interface, APIs, services, and tools means that end users and computer professionals do not have to learn different interfaces or tools. An integrated solution offers easier management, better connectivity, and lower support costs, and because NetShow and Microsoft Internet Information Server are designed to work together, they combine to deliver a complete, well-tested, and high-performance system for broadcasting multimedia.

Server scalability. Because NetShow has been designed specifically for Windows NT Server, it is fully optimized to take advantage of Windows NT Server's high scalability to provide both small-scale implementation, and easy upgradability to higher performance systems. NetShow can easily adapt to an organization's growth. NetShow scales to very high-performance, enterprise-class multiprocessor systems with many gigabytes of memory and terabytes of storage, and exploits the ability of Windows NT Server to run on leading-edge microprocessors such as Intel Corporation's Pentium and Pentium Pro, and Digital Equipment Corporation’s Alpha. Microsoft internal tests have shown that a NetShow server can handle over 1000 streams of data at 28.8 kbps on an industry standard Pentium Pro-based uniprocessor computer with 64 MB of RAM, with no impact on the quality of the content and services delivered to clients.

Server Content distributionpropagation. NetShow 2.0 enables the server to be partitioned into several components that can be installed on different Windows NT Server based computers. This feature allows the delivery of a higher number of streams, to provide services to an otherwise unserviceable number of clients, and also optimizes the server infrastructure used to distribute content to clients. This optimization enables the installation of a geographically distributed array of NetShow servers, to optimize how content is distributed from the source to clients, and also enables an array of less powerful and expensive computers to be deployed, rather than a smaller number of more powerful and costly platforms. The server infrastructure can consist of a geographically distributed array of NetShow servers, to optimize how content is distributed from the source to clients. The array, in turn, can consist of many small, inexpensive computers, rather than just a few powerful but costly platforms.

Server administration and management. NetShow 2.0 provides a very flexible way of deploying audio and video broadcast services over the Internet or within a corporate intranet. NetShow server can run on single or multiple computers, and has a Web-based administration interface for complete monitoring and remote administration. This rich, robust functionality, in addition to easy-to-use setup routines and tight integration with Windows NT Server, makes NetShow 2.0 a powerful yet easy system for broadcasting. Customers will benefit from faster deployment of custom solutions as well as reduced training and support costs.

NetShow administration is provided through an intuitive Web-based interface, which enables both local and remote administration. This lets administrators manage server installations, and make configuration changes, without having to physically access each server. Administrators can also set the maximum content throughput per file and per server, to control network bandwidth utilization. NetShow administration runs on both Windows NT and WindowsÒ 95 operating systems.

NetShow has been designed to utilize Windows NT 4.0 server administration features such as the Event Log and Performance Monitor, which indicates the number of streams going out from the server, the percentage of CPU time being taken by the NetShow services running, and other performance related data. An additional advantage here is integration with tools that developers are already familiar with.

Monitoring and logging events. NetShow includes tools for monitoring and logging events: the Monitor Events Log is used to display events and the NetShow Server Event Log is used to store events in a database. Both tools allow you to filter events by type: server, client, administrative, and alert. Server events indicate server status; for example, whether a server is online or offline. Client events are logged, for example, when a client connects or disconnects. Administrative events are logged when configuration settings are modified; for example, when the maximum number of clients or maximum bandwidth is modified. Alerts are logged when server configuration settings are exceeded; for example, when the maximum number of clients is exceeded.

Content management. Content can be stored on a hard drive, and whenever that data is published to a Web server and to clients, virtual directories can be created. This is especially helpful when content is being added and removed on a daily, or even more frequent, basis. And, as noted earlier, it is possible to place limits on the throughput of a server, or limit the bandwidth available for streaming certain files, for example. These are functions corporate network managers will require before deploying a server on their intranets.

NetShow 2.0 opens a new set of opportunities for Web-based broadcasts similar to current TV broadcasts. NetShow 2.0 enables content to be configured and scheduled for later delivery, and allows the generation of announcements to users of upcoming and in-progress sessions. The content scheduling mechanism is based on a channel metaphor users are familiar with, and the system is designed to allow a server to have multiple channels. By way of analogy, a cable company manages multiple channels, such as CNN, NBC, and others, which are organized in a numeric sequence to make television surfing easy. In this example, CNN might be channel 3, NBC channel 5, and so on. Each channel also has time-based programs, such as the 10:00 PM news, or a movie at 11:00 PM. Users can easily find their favorite programs, because they know when and where to look. Following this same paradigm, NetShow 2.0 makes it possible to organize audio and video content into separate channels, each of which has scheduled programs, in addition to announcements of current or upcoming sessions.

Server Administration Software Development Kit (SDK). The NetShow Server SDK supports the creation of NetShow Channel Manager administrative applications using the Channel Manager ActiveX control and the creation of NetShow Unicast administrative applications using the Unicast ActiveX control. Independent software vendors and Solution Providers can build customized administration utilities using this software development kit.

Restricting access to NetShow Server. It is possible to control client and server connections to NetShow Server and the Real-Time Encoder based on the IP addresses of the clients or servers attempting to connect. Access is controlled by creating a list of addresses in the Windows NT registry. By default, all connections are allowed.

Networking services: transport protocols. NetShow supports a variety of network transport protocols, including UDP/IP, TCP/IP, HTTP, RTP, and IP multicast. Support for these standards facilitates integration with low-level network technologies, resulting in better delivery of multimedia content. Because NetShow supports HTTP, clients behind firewalls can receive NetShow broadcasts without compromising the firewall security features. The client software automatically selects appropriate settings upon installation, and selects the proper protocol for use by the server. This eliminates the need for system administrators to manually specify the mechanism to be used.

Managing network transport: intelligent fail-over. The broad range of network transport protocols supported by NetShow allows content providers to choose the protocol most effective for delivery of their content, depending on the application scenario and network infrastructure available. NetShow allows content to be delivered using IP multicast, UDP/IP, TCP/IP, RTP, and HTTP, thus supporting a wide range of deployment scenarios. In addition, NetShow is optimized to reduce content delivery losses due to changes or obstacles in the network infrastructure. For example, NetShow exploits the benefits of IP multicast on multicast-enabled networks, automatically falls back to unicast UDP/IP traffic if necessary, then to unicast TCP/IP and finally to HTTP traffic if unicast UDP/IP cannot be delivered by any means. This powerful feature allows content providers to use NetShow to broadcast content using either unicast or multicast techniques without worrying about the nature of the available network infrastructure. NetShow will automatically fail-over from multicast to unicast mode, and from UDP/IP to TCP/IP and HTTP transmission to ensure content delivery. This feature also allows content to be sent through firewalls, allowing corporate users to view NetShow content as easily as other users.

Firewall support. To prevent unauthorized access to their networks, corporations deploy firewalls. Most firewalls are based on packet filtering. In packet filtering, the computer examines the source and destination IP addresses of a packet and forwards only those packets for which access has been granted. The content streamed from Microsoft NetShow can stream through a number of firewalls from vendors such as Ascend Communications Inc., CheckPoint Software Technologies Ltd., Cisco Systems, Computer Software Manufacture, Cycon Technologies, LanOptics Inc., Firewall System, Microsoft Corporation, Milkyway Networks, Secure Computing, and Technologic Inc. In addition, several additional vendors are working to add support for NetShow 2.0 to their products. The NetShow Web site lists the firewall products currently supported. This page will be updated periodically as additional firewall vendors announce support for NetShow.

Content type: audio, video, and illustrated audio. NetShow can deliver both audio and video content at different bit rates, starting from audio optimized for 14.4 kbps dial-up connections to stereo quality audio optimized for ISDN connections, and from video optimized for 28.8 kbps connections up to video optimized for 6 Mbps delivery. The ability to deliver illustrated audio content is also critical for optimizing content delivery and using network bandwidth efficiently. Illustrated audio allows ideas and information to be shared on narrow-band networks. Illustrated audio is similar in concept to an on-line slide show, where audio is synchronized with specific images such as Microsoft PowerPoint slides to create an interesting and effective interactive multimedia presentation. When working with video material, a content author can use illustrated audio to select key frames to illustrate and augment a sound track, while avoiding the problem of random frames often seen with slow-scan or reduced frame rate systems. As more bandwidth becomes available, the content author can increase the frame rate, image size, and quality of the individual images. This trade-off between the bandwidth available on a given network and demands for quality and performance determines how content authors should develop their illustrated audio content.

Rich, synchronized multimedia experience. NetShow 2.0 provides live and on-demand streaming of audio, illustrated audio, and video synchronized with pictures (JPEG, BMP, GIF files) as well as script (Jscript and ActiveX script), URLs and text. The result is a compelling mixed-media experience. Content providers can now generate sophisticated productions in which graphics, slides, photographs, and URLs can all be synchronized with audio and video streams.

File format. The Active Streaming format (ASF) is an open, standards-based multimedia file format, which allows content and tool developers to work to a shared specification that supports the authoring, combining, archiving, annotation, and indexing of synchronized media objects without regard to original media formats or underlying transports. Active Streaming format allows multiple types of data—for example, audio objects, video objects, still images, URLs, and HTML pages—to be combined into a single synchronized multimedia stream that can be stored on a variety of servers and transmitted over a range of networks.

As files stream across a network, it is possible for packets of information to be lost, particularly on the Internet. When packets are lost, the viewer can experience choppy play, loss or gaps in the audio, and even loss of entire images. If packets stop being delivered, the NetShow player stops rendering until it can rebuild its buffer. To improve performance when packets of information are lost during transmission, it is possible to use NetShow error correction and concealment facilities included in the file format. For example, the ASF Editor and ASF Real-Time Encoder can optionally include this redundant error-correction data in the stream, which enables the NetShow player to correct for certain levels of packet loss. If there is extreme packet loss (to the point where error correction is not possible), the player masks the errors. For audio masking, the player uses neighboring audio information to conceal the loss of data. For image masking, NetShow supports conversion of images into loss-tolerant .jpg images, which the NetShow player can then utilize to minimize the lost of data packet, as opposed to discarding the entire image.

ASF files can be stored on traditional file servers, HTTP servers, or specialized media servers. The lack of data communications dependencies within ASF allows ASF data to be carried over a wide variety of transport protocols, including TCP/IP, RTP, ATM, and UDP/IP.

Broad variety of audio and video compression. NetShow 2.0 provides a wide range of audio and video compression models to satisfy the needs of different forms of content at different network bandwidths and bit rates. NetShow provides a basic and an enhanced approach to compression. The basic approach provides the default compression technologies so that content providers can start streaming content immediately. This means high quality audio and video content, but a smaller download and fewer codecs to choose from, to benefit those who are new to developing streaming content. The enhanced approach allows more experienced content developers to select the codec that best suits the content they are working on. This approach means a wide variety of codecs to choose from, but does mean a larger download for the client.

• Basic approach. The basic approach includes the following standard base audio and video codecs.

• Enhanced approach. The satisfaction of the viewer with the network experience depends greatly on compression technology. NetShow includes over 20 audio and video codecs to satisfy the needs of the great majority of content providers. In addition, any codec that is compatible with the Audio Compression Module (ACM) or Video Compression Module (VCM) interface can be used with NetShow, providing even greater flexibility for content compression and authoring.

A partial listing of the audio codecs supported in NetShow 2.0 is described in the following table.

The following video codecs are installed with Microsoft NetShow.

NetShow authoring tools. In order to choose the correct tool, users should understand the basic types of NetShow content. NetShow authoring tools take source information (either in live or stored form) and turn it into the Active Streaming format that NetShow Server can easily stream. Live information can be anything you can feed into your audio or video card, including a CD player, microphone, VCR, or video camera. Stored information can be .avi, .wav, .jpg, or .bmp files. Once the media has been converted to the Active Streaming format, you can deliver it to NetShow Server for streaming either as a stored .asf file or as a live ASF stream.

• On-Demand Content. Microsoft's primary content creation tools are the ASF Editor, VidToAsf, WavToAsf, and Publish to Asf. The NetShow ASF Real-Time Encoder is primarily a tool for creating live content; however, it can also be used to generate on-demand content. In addition to the growing number of Microsoft NetShow content creation tools, there are also an increasing number of third-party tools that output .asf files. The following list briefly describes the Microsoft NetShow tools.

• ASF Editor. Provides a graphical interface for combining and synchronizing audio and image files. The ASF Editor can display a simulation of what an ASF file will look like before it is created. The ASF Editor also helps create ASF files for restricted network bandwidth and adds error correction. The ASF Editor can include URLs and other types of script commands in the ASF file.
• VidToAsf. A command-line utility that converts AVI or MOV files into ASF files. Using a command-line option, users can also specify script files that will add markers, invoke URLs, and execute script commands.
• WavToAsf. A command-line utility that converts WAV files into ASF files. Using a command-line option, users can also specify script files that will add markers, invoke URLs, and execute script commands.
• Publish to ASF. A PowerPoint add-on tool (shipped with Office 97) that saves PowerPoint slides and accompanying audio clips together as a single ASF file. Using the Narration tool in PowerPoint, users can create an audio clip for each slide in their presentation. At any time, users can create an ASF file from a current presentation by using the Publish to ASF tool.
• PowerPoint Internet Assistant. A PowerPoint add-on tool (for use with the version of PowerPoint shipped with Office 95) that turns all slides in a presentation into .jpg images. Users can then create an ASF file using ASF Editor.
• ASF Real-Time Encoder. The Real-Time Encoder turns any live source (such as output from a microphone or a video camera) into an ASF stream or ASF file. The Real-Time Encoder can also be used to convert an AVI or WAV file to an ASF file.
• ASFChop. ASFChop is an ASF file-editing tool. Use ASFChop to trim time from the start or end of an ASF file.

In addition, third-party tools vendors such as Vivo, Sonic Foundry, and Digital Renaissance and others have value-added authoring tools designed to work with NetShow 2.0, giving customers a choice from a wide variety of tools for content creation.

• Live Content – The NetShow Real-Time Encoder. The Real-Time Encoder encodes live or stored audio and video into an ASF stream, an ASF file, or both. The Real-Time Encoder is an extremely useful NetShow content creation tool. It combines real-time audio, video and/or text into a single stream according to the bandwidth requirements specified.

To make it simple to set up and run the Real-Time encoder, NetShow 2.0 ships with a large selection of preconfigured encoder settings. These are represented by Active Stream Description files, or ASDs. These settings make it as simple as double-clicking to begin encoding for a talking-head broadcast for the Internet, CD-quality audio for the intranet, and so on.

For the advanced content author, the NetShow Real-Time encoder supports an OLE automation interface. Content authors and developers can embed the encoder into their applications and completely circumvent the encoder’s GUI. Developers can use Visual Basic or Visual C++ development systems to control the Real-Time Encoder.

• NetShow Presenter. NetShow Presenter is a Microsoft PowerPoint 97 add-on tool that helps users simulate live streaming of a PowerPoint presentation. For example, workers in Chicago link to a company Web page to watch their CEO, in Los Angeles, deliver a speech and PowerPoint slide presentation. The workers in Chicago are able to see the CEO deliver his speech on the NetShow player embedded in a frame in the Web page. In a different frame in the Web page, the slides will appear. As the CEO switches slides, the slides switch in the Web page. This is made possible by combining the Real-Time Encoder, NetShow Server, an FTP and HTTP server, PowerPoint 97, and NetShow Player. NetShow delivers an integrated mechanism to support this scenario.

Running the NetShow Player. There are two ways of using NetShow Player to play content:

• As a stand-alone player. When you use NetShow Player as a stand-alone application, you can decide how you want to access the NetShow content. If you play the NetShow content file locally, you are not streaming the file. NetShow Player reads the content file from the hard drive and then plays it. If you play a content file from a remote location, it will stream to your computer. You can launch the stand-alone player from a link in a Web page.
• Embedded in a Web page, Visual Basic script application, or other ActiveX container application. An easy way of providing NetShow Player to people who don't already have it on their computers is to embed the player in a Web page. When a user accesses the page, the player is optionally downloaded. The script commands used to embed the player can identify the NetShow content to play as well as how to play it. The player's properties can even be set to check the version of the player on the computer. If the player is outdated, the computer downloads the newest version.

Client Software Development Kit: rich programmability. The NetShow player is built on ActiveX technology. The NetShow client ActiveX control provides an extraordinarily rich set of client APIs, which enable clients to harness the power of a comprehensive set of broadcast applications. Web masters, systems integrators, and developers can quickly and easily use the NetShow ActiveX control functionality to create custom business solutions using a variety of visual programming tools. Because the Player control is an ActiveX control, a developer can create applications in Microsoft Visual Basic, Microsoft Visual Basic Scripting Edition, Microsoft Visual C++, Microsoft Visual J++Ô or any language that will work with ActiveX controls. The Software Development Kit for the NetShow player is included in NetShow 2.0 and is also part of the Internet Explorer 4.0 Software Development Kit (SDK).

Client cross-platform support. Support for cross-platform clients is a key customer requirement for NetShow. The current beta of NetShow 2.0 provides client support for both the Windows 95 and Windows NT operating systems, and the client software has been enhanced to further facilitate cross-platform portability. The NetShow client for Windows 3.1, Macintosh, and UNIX platforms is scheduled to be available within two months of the NetShow 2.0 release.

Integration with Microsoft Internet Explorer 4.0. The NetShow player is now an integral part of Internet Explorer 4.0. While installing the Internet Explorer 4.0 enhanced or full configurations, the NetShow player is installed automatically as part of the browser. NetShow brings the power of broadcasting to Microsoft Internet Explorer, enabling it to receive a new class of innovative interactive content. NetShow enables the synchronized streaming of audio and video with other Web page elements, such as URLs, to increase the impact of content delivery. The NetShow client can forward the received URL addresses to Internet Explorer, allowing a new Web page to be displayed in either the browser window or a frame contained within the page currently being viewed. Image and video hotspots can also be created. While hyperlinks and image maps are a common concept in Web pages, they have been limited to text or a static image. NetShow enhances hyperlinks and image maps by associating user interactivity with defined regions on dynamically changing images, or even video. Additionally, Visual Basic or JavaÔ scripts can be combined with NetShow content to enhance broadcasting with a multitude of Visual Basic and Java capabilities. The retrieval of live data will facilitate the development of specialized programs and generally enhance the user experience by providing a new class of interactive content.

NetShow plug-in for Netscape Navigator. NetShow 2.0 includes a Netscape Navigator plug-in that enables Web surfers using Navigator to view Web-based NetShow content.

Support for Intel’s MMX processor. NetShow receives a significant performance enhancement from the Pentium II processor. MMX optimization enhances the performance of the NetShow player by up to 40 percent and the NetShow Real-Time Encoder by up to 90 percent. For example, an executive using an MMX technology-equipped laptop can now deliver live video coverage of his or her product presentation to an audience of thousands on the Internet. The performance boost for NetShow is possible because the MPEG-4 codec included with NetShow is optimized for MMX technology.

This document is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS OR IMPLIED, IN THIS DOCUMENT.

© 1997 Microsoft Corporation. All rights reserved. Microsoft, ActiveX, Jscript, NetShow, PowerPoint, Visual Basic, Visual C++, Visual J++, Jscript, Windows, and Windows NT are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. Java is a trademark of Sun Microsystems, Inc. Other product and company names mentioned herein may be the trademarks of their respective owners.