Terms - Page 2

Here are some terms that need to be defined before we can discuss Windows Media specifically and streaming media in general.

• Streaming: The real time delivery of digital video or audio to an end user without needing to download the content to the local hard drive before playing. Data is delivered just in time for it to be played back in the media player.

• Bandwidth: Data capacity. The amount of data that can be pushed through a data connection in a certain amount of time. Dial up connections are generally 56kbits/sec. DSL and cable modem connections are 256 kbits/sec or greater, T1 lines in an office are 1500 kbits/sec (1000 kbits = 1 Mbit).

• Encoding: The compression of a digital video file into a specific format using a video codec. With streaming media it refers to taking either an analog tape, such as VHS, or a digital AVI file and processing this using the Windows Media, Real, or Quicktime codecs to create a compressed digital video file. Encoding to a streaming format allows the file to be played as it downloads. With earlier Quicktime and AVI files the whole file had to be downloaded before playback could begin. Encoders accept live or stored content.

• Codec: Codec is short hand for Compression/Decompression. A mathematical algorithm that allows media files to be compressed in size. The Windows Media codec compresses the video to such a degree that it is suitable for delivery over the Internet. In the Media Player the video is then decompressed for playback. Codecs are linked to processor speed, this is why codecs have been able to compress more efficiently as computers have gotten faster.

• On-Demand Encoding: When video is encoded from a stored file such as an AVI then it is being encoded on-demand.

• Live Encoding: Live encoding is taking a video signal from a live event and encoding it as fast as it happens. Even in a real time event there may be some delay (as much as 18 seconds) this is called near real time encoding. If the delay remains constant and doesn't increase this is still considered Live encoding.

• Real Time: Real time and near real time mean that the encoder processes the video as fast as it is happening. This is especially important for live events where the encoder would get further and further behind if it was not doing real time encoding. Only within the last two years have computer processor and encoding software gotten to the point where they can encode fast enough to keep up with live video.

• Multicast: Like a broadcast, a multicast replicates information from one source to multiple recipients on a network. Multicasting saves bandwidth, but due to the current configuration of the Internet it is not possible to do a multicast to all users on the Internet. Multicasting works best on closed networks. UUNet has multicast enabled portions of their network as does Excite@Home's cable modem services. Currently multicasts are best done on closed corporate networks or over satellite using service providers such as Loral Cyberstar. As an example, if one 300kbit/sec multicast was done to 300 people on a corporate 10 base-T LAN then only 300kbit/sec would be used on the LAN and all 300 people could see it. If unicast were used then only 33 people could see it before all the bandwidth was used. Multicast is best for large events.

• Unicast: When one user watches one video stream. Thus a new connection must be established for each additional user. Very bandwidth intensive for large events.

• Media Player: The media player is the software on the client computer that decompresses the streaming video or audio using a codec and plays it back on the computer screen. The media player can be used as a stand alone application or embedded in a Web page to create a video application interacting with HTML content.

Why Streaming?

Why use Windows Media streaming video and not distribute on videotape or closed circuit TV? For users and companies taking their first steps into video Windows Media is the cheapest solution. The Windows Media Server is bundled for free with Windows NT 4 and Windows 2000 Server. The software tools that enable encoding are also free and freely downloadable from Microsoft's Site. I'll talk more about these tools later in the article. Cost is only one factor; there is also the near ubiquity of the Windows Media Player and the Web browser on user desktops.

If creating and hosting the service internally requires more staff than is acceptable then outsourcing may be an option. Services such as Akamai and Yahoo provide streaming over the public Internet. For a limited number of low quality streams this can be a good solution. If you want to provide high quality streams that can be multicasted across your network to save bandwidth then you need to look to a satellite provider such as Loral Cyberstar.

Windows Media Player is bundled with Windows 98, 98SE, ME, NT 4 and 2000. If a user has an older version the player will initiate a download of the latest version. The Media Player combined with a Web browser on every desktop means that the playback mechanism is present on nearly every corporate and consumer desktop. Combine this with the Windows Media Server bundled on the Windows Server and you have both ends of a video broadcast system.

With older video distribution the user had to go to a room with a closed circuit TV or VHS player. Now the user can view the video at their desktop. Using the Internet the user can be monitored to see how long they viewed the video and give feedback on its usefulness and quality. These services are just starting to become available through services providers such as Loral Cyberstar over satellite and Akamai via terrestrial links.

Windows Media: Encoding
Windows Media: Encoding
Shooting Streaming Video - Page 3