Compaq ProLiant 1600 Video Streaming Technology - Page 15

ECG068/0798 WHITE PAPER (cont.) 1...5 Step 1. Capture: As this diagram shows, the first step in the process of creating streaming video is to "capture" the video from an analog source such as a camcorder or VHS tape, digitize it and store it to disk. This is usually accomplished with an add-in analog video capture card and the appropriate capture software. Newer digital video sources such as digital video camcorders can be captured straight to disk with a "Firewire" capture board without the analog-to-digital conversion step. The capture card may also support the delivery of "live" video in addition to "stored" video. Step 2. Edit/Author: Once the video is converted to digital and is stored on disk it can be edited using a variety of non-linear editing tools. At this stage, as described below, an authoring tool may also be used to integrate the video with other multimedia into a presentation, entertainment, or training format. Step 3. Encode: After the video is edited and is integrated with other media it may be encoded to the appropriate streaming file format. This generally involves using the encoding software from the video-streaming vendor and specifying the desired output resolution, frame rate, and data rate for the streaming video file. When multiple data rates need to be supported, multiple files may be produced corresponding to each data rate. As an alternative, newer video streaming technologies create one file that has "dynamic bandwidth adjustment" to the needed client data rate. Step 4. Serve: The video server manages the delivery of video to clients using the appropriate network transport protocols over the network connection. The video server consists of a hardware platform that has been optimally configured for the delivery of real-time video plus video server software that runs under an operating system such as Microsoft Windows NT that acts as a "traffic cop" for the delivery of video streams. Video server software is generally licensed by the "number of streams." If more streams are requested than the server is licensed for, the software rejects the request. Network connections in the Enterprise are generally 10/100BaseT switched Ethernet or Asynchronous Transfer Mode (ATM), while over the public Internet they are IP-based packet-switched networks using dial-up modems, ISDN, or T1 lines. Step 5. Play: Finally, at the client station the video player receives and buffers the video stream and plays it in the appropriate size window using a VCR-like user interface. The player generally supports such functions as play, pause, stop, rewind, seek, and fast forward. Client players can run stand-alone or can be ActiveX controls or browser plug-ins. They can decode video using software or using hardware add-in decoder boards. Network Considerations Not all networks are well suited to the transmission of video. The high bandwidth time-critical nature of video imposes unique demands on network infrastructure and network protocols. Three of the most important characteristics of networks for video transmission are: 1. High Bandwidth 2. Quality of Service (QoS) 3. Support for Multicasting High Bandwidth-Digital video can come in many different bit rates. Generally, High-Bit-Rate (HBR) video is 1.5Mbps-the rate of MPEG-1-or above, and Low-Bit-Rate (LBR) video is 64Kbps-a single ISDN channel-or less. HBR video needs a high bandwidth network such as a corporate Intranet as a delivery vehicle, while LBR video can go over a network such as the public Internet.