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Creating High-Quality Content with MS Windows Media Encoder 7
Published: July 1, 2000
Summary: This document is a brief tutorial on how to use the new features in Windows Media Encoder 7 to create high-quality video content from television, film, and screen sources. This article assumes that you have a basic understanding of streaming, compression, and audio/video production. (6 printed pages)
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Microsoft® Windows Media™ Encoder 7 is a powerful, easy-to-use, production tool that enables content developers to convert both live and prerecorded audio, video, and computer screen images to Microsoft® Windows Media™-based content for live and on-demand delivery. Windows Media Encoder enables new capabilities for the type and quality of audio and video content you can create for the Web.
Producing audio and video for the Web is as much art as it is science. While this document is not meant to clear up all of the mysteries of content creation, it does provide a very targeted, step-by-step introduction to this version of Windows Media Encoder and will get you started on some of the new capabilities available in Microsoft® Windows Media™ Technologies.
This document covers the following topics:
Capturing and Encoding Screen Content
The screen capture feature of Windows Media Encoder enables you to capture your entire desktop, individual windows, or a region of the screen and broadcast them or encode them to files just as you would any other content. In addition, the encoder enables you to use the Windows Media Screen codec version 7.0 to convert existing files for efficient Web delivery.
You can use the encoder to:
Note: Artifacts can be introduced when an analog signal is run through a scan converter and converted to the National Television Standards Committee (NTSC) standard. These artifacts are amplified during encoding and can degrade the quality of the encoded video.
The encoder enables you to capture directly to a Windows Media file or to broadcast your session live. The session can be broadcast and archived simultaneously.
Because of the amount of data being manipulated and the CPU power necessary to compress it quickly, capturing screen images is a performance-intensive process. Therefore, the power of your computer, the size of the screen being captured, the color depth of the display (256 colors, 16-bit, and so on), and the specified frame rate all have an effect on performance. Also, the quality of your encoded screen images can be affected by the amount of motion that occurs during the encoding process. The Windows Media Screen codec is designed specifically for capturing large areas that involve little movement. Using this codec to capture a motion video, for example, will not give good results.
To ensure that the screen you capture will encode and play well:
If you are capturing to a file, the main encoder window is minimized while the screen is being captured so you can monitor the encoding statistics and the input and output images. Restoring the window to its regular size stops the encoding session. If you do not want the encoder window to minimize while a screen is being captured, on the Tools menu, click Options, click the General tab, and then clear Minimize main window to capture screen.
Note: If you are capturing a screen for broadcast and have selected a broadcast port, the encoder window does not minimize while the screen is being captured. Broadcasting a screen capture session overrides the Minimize during screen capture session, then stop on restore setting on the General tab.
Windows Media Encoder includes three system profiles that make use of the Windows Media Screen codec. Use them when capturing a screen directly from the encoder or when sourcing from files (such as .avi) that contain screen capture content. The three screen capture profiles are:
To Capture and Encode a Screen Using New Session Wizard
To Encode an .AVI File Containing Screen Content Using New Session Wizard
Using Video Optimization Filters
What most of us know as "video" is defined by the National Television Standards Committee (NTSC), which requires that analog data be interlaced and broadcast at 30 fps (or 25 fps for Phase Alternate Line (PAL) video). Interlaced video displays an image using a half-resolution video image known as a field, and uses two video fields to make a single frame of video. Each field of video is made up of every other line. Field one displays all the odd numbered lines, then field two goes back and displays all the even numbered lines. Interlacing saves bandwidth when the video is transmitted over the air or on cable, but the video quality suffers when interlaced content is transferred to a digital format. This affect comes into consideration for many different content sources, such as DV cameras, VHS tapes, 8mm, and TV sources such as cable. The Windows Media Encoder can de-interlace the content, filtering the alternate fields into a single frame to achieve a smoother result.
Film is normally shot at 24 fps. When transferred to another medium, such as DVD and videotape, extra fields are added to the content to achieve the standard 30 fps required by NTSC using a sequence called 3:2 pulldown. The extra frames are added in a telecine room, where the film to video transfer takes place. Windows Media Encoder can remove the added fields of video and encode the image at 24 fps, resulting in a smaller file size and higher quality image. The process of removing the extra frames is called inverse telecine. PAL video does not need these extra fields of video as the frame rate is close enough that the film is just transferred at 25 fps.
To Deinterlace Video
To Convert Film-Based Content From 30 FPS to 24 FPS (Inverse Telecine)
Encoding High-Motion Content at 60 FPS
Windows Media Encoder contains several high-motion profiles that enable you to encode high-motion content, such as a sporting event at 60 fps and 320 x 240 resolution. High-motion content is content that contains a lot of movement but few scene changes.
To produce content at 60 fps, begin with a source that is interlaced at full-height resolution. Full height for NTSC is 480 pixels. The resolution must be full height so the encoder can capture all the interleaved fields.
During the encoding process, you deinterlace the content to produce two half-height 30 fps frames that are joined together into a single frame and played at 60 fps.
To Encode High-Motion Content
For More Information
To learn more about Windows Media Encoder, see Windows Media Encoder Help. To learn more about encoding configuration and hardware requirements, and to download the Encoder 7, see the Windows Media Encoder page on the Windows Media product site ( http://www.microsoft.com/windows/windowsmedia/WM7/encoder.aspx ).