Contents

Introduction

Back to Top

Usage Scenarios

When Do I Use the Windows Media Screen Codec?

• You can capture and encode content directly from the screen by using Windows Media Encoder and the Windows Media Screen codec.
• You can capture content by using other screen-capture programs, and then convert that content to Windows Media Format by using Windows Media Encoder.

Capturing Directly with Windows Media Encoder

Using Third-Party Tools with Windows Media Encoder

Should I Use Version 7 or Version 9 of the Windows Media Screen Codec?

Back to Top

Best Practices

Adjusting Audio and Video Settings Before Screen Capture

• Set the screen resolution.
  First determine the screen resolution at which the majority of your users will view the content. Then, on the computer where you will capture the content, set that same screen resolution in Control Panel in the Display Properties dialog box. For example, if most users will view the content in an 800x600 window, capture your content at a resolution of 800x600 or lower.
  When you capture content at a lower resolution than users are viewing on their screens, Windows Media Player displays a border, the controls are visible, and the content is legible. If you capture the content at a higher resolution than users are viewing on their screens, the streaming content will be resized to fit the Player window, and the quality and legibility of the content may be seriously degraded.
  The Windows Media Screen codec will accept screen resolutions from 32x32 pixels to 2048x2048 pixels. However, note that using the screen codec with other applications may not provide the same resolutions as indicated. Capturing content at a 1024x768 resolution yields more data than capturing at 640x480, so use a lower screen resolution whenever possible. A resolution of 800x600 or lower is recommended.
  Also note that the screen resolution that you select is not the same as the frame size that you use to capture the screens. For example, you might set your screen resolution to 800x600, and then capture a frame size of approximately 640x480 pixels.
• Do not use a background image.
  Having an image in the background of your screen capture increases the amount of data, so it is recommended that you turn off the screen's background image. In Control Panel in the Display Properties dialog box, choose None for the background.
  This same recommendation also applies when you capture a window of PowerPoint® slides. To reduce the amount of data that must be encoded, sent, and decoded, avoid elaborate graphical backgrounds on your slides.
• Decrease the color quality.
  Decreasing the color quality reduces the amount of data that the graphics card must process. In Control Panel in the Display Properties dialog box, set the color quality to 8-bit or 16-bit color. Many modern graphics cards do not have an 8-bit color quality option, and in many cases, 32-bit color will be captured at higher capture frame rates than 16-bit color.
• Turn off font smoothing.
  Fonts that have the edges smoothed do not compress well. In Control Panel in the Display Properties dialog box, use the Effects options on the Appearance tab to turn off font smoothing.
• Turn off hardware acceleration.
  Hardware acceleration can decrease the video quality because it moves some video data processing to the graphics card, which accelerates the CPU processing but slows the ability of the Windows Media Screen codec to read the video data. By turning off hardware acceleration, the video data is stored in main memory and processed by the CPU; therefore, the data can be read faster by the Windows Media Screen codec. In Control Panel in the Display Properties dialog box, use the Advanced options on the Settings tab to turn off video hardware acceleration.
• Use a Windows Classic theme to avoid dithering effects.
  To avoid the dithering effects of the standard Windows XP display appearance, in Control Panel in the Display Properties dialog box, change the theme to Windows Classic.
  Alternately, if you want to maintain the Windows XP appearance, do the following:
  1. In Control Panel in the Display Properties dialog box, click Appearance, and then click Advanced.
  2. On the Advanced Appearance dialog box, for Item, click Active Title Bar, and then for Size, type 21.
  3. For Color 1 and Color 2, select the same color. To do so, set Color 1 as a custom color, and then set Color 2 to that same custom color.
  4. Repeat steps 2 and 3 for each item that you need to adjust.
• Close all other applications.
  Before you capture content, close all other applications that you are not using so that they do not affect the availability of system resources while you are capturing screens.
• Maximize the audio quality.
  If you plan to capture and compress data from a computer screen directly (as opposed to creating an .avi file), and you plan to use audio, take steps to maximize the audio quality. For example, use a high-quality microphone, and consider using a room designed to minimize background noise.

Setting up Producer

• Create a custom template and profile.
  If you want to use Producer to capture screens at resolutions higher than 800x600, create a custom template and profile to capture the screen images at these higher resolutions. For more information about creating a custom template and profile, see Producer Help. You can download Producer from the Producer 2003 page.
• Use a remote desktop connection.
  The recommended configuration for screen capture is to run Producer on your primary desktop, and then capture screens from a remote computer. This configuration distributes the workload between the two computers. You can set the capture properties, including the display size and color depth of the remote computer, by using the Display tab in Remote Desktop Connection options.

Preparing Hardware

• Use a fast processor and graphics card.
  Capturing screens is a performance-intensive process that requires a powerful CPU and a fast graphics card. For the best results, use the fastest processor you can obtain or better yet, use a computer with multiple fast processors. The graphic card also makes a significant difference in the screen-capture performance. Use a graphic card with a very fast bit block transfer (BitBlt) in order to quickly retrieve the frame buffer from video RAM (VRAM) to system memory. For more information about the recommended computer configuration for capturing screens, see Recommended Configuration.
• Check the hardware interrupts.
  Check the interrupts to make sure that the audio and video cards are not using the same interrupt request (IRQ). This issue is common for laptop computers.
• Uninstall unnecessary audio cards.
  Uninstall the motherboard audio and any other audio cards that you are not using. Multiple cards compete for resources, including the IRQs, even if the cards are not actively being used.
• Use one monitor only for capturing content.
  If you have a multiple-monitor system, make any necessary adjustments so that you can capture all screens from the primary monitor only.

Capturing Content

• Make sure that your screen capture and encoder settings are in sync.
  If you are using another software program to capture your content, and then you are encoding that content using Windows Media Encoder, make sure that the settings of the two programs are in sync. For example, you do not need to capture content at 30 frames per second (fps) if you are going to encode that content at a peak bit rate of 4 Kbps and a frame rate of 5 fps. In fact, this scenario may overload the bit rate with the frame rate and cause the Windows Media Screen codec to miss scene changes within the content. Therefore, capture and encode your content using the same bit rate and frame rate.
• Capture content for .avi files in uncompressed format.
  If you are using other screen-capture, editing, or post-production programs, make sure that your content is captured and edited in an uncompressed format. The goal is to keep the content in uncompressed format from when it is captured until it is ready to be compressed in Windows Media Encoder. Many programs have default settings that automatically compress content, and this compressed format may degrade the quality of the encoding content in Windows Media Encoder.
• Avoid capturing the entire screen display area.
  Capture only the application window or applicable region of the screen, choosing the smallest area possible.
• Minimize the number of graphics.
  Minimize the number of graphics in the capture area. For example, do not capture unnecessary advertising frames and associated graphics on Web pages.
• Use the lowest frame rate possible.
  Consider the average frame rate for users' computers that will be downloading the content, and capture content using the lowest frame rate possible. You may have to experiment with the setting to determine the frame rate that meets your needs.
• Reduce the number of on-screen activities.
  Consider the types of screen activities that can be accommodated by your average frame rate. For example, a frame rate of 3-5 fps will accommodate basic mouse activity and limited typing. To improve video quality, avoid or minimize the occurrence of the following screen activities, which can be difficult to compress or require additional bandwidth:
  • Opening and closing windows. As with camera video, the quality of application video degrades with excessive motion. Whenever possible, avoid rapidly opening and closing windows.
  • Dragging windows across the desktop. Dragging windows might result in dropped frames, because this type of movement makes it impossible for the codec algorithms to have a consistent frame of reference to compute data. If dragging windows is necessary, in Control Panel in the Display Properties dialog box, use the Effects options on the Appearance tab to turn off the visibility of windows contents when you drag.
  • Zooming in and out. This activity can cause content to blur, which is difficult for the Windows Media Screen codec to capture and reproduce. Content will look best when it is captured at 100% of its original size.
  • Scrolling up or down on a Web page. Scrolling makes it difficult to maintain a consistent reference point, resulting in dropped frames. This issue underscores the importance of creating content at the appropriate resolution. Using the PAGE UP or PAGE DOWN keys may be an acceptable alternative.
  • Displaying images containing great variation in color depth. It is difficult to compress an image when there is significant variation in color from one pixel to the next. The result may be dropped frames of data.
  • Using the Windows Media Screen codec to capture a screen that includes a window in which camera video is playing. Compression of camera video and compression of application video are two very distinct techniques. Using the Windows Media Screen codec to compress camera video can result in less than optimal results. You should use a video codec, such as the Microsoft Windows Media Video codec, to compress camera video.
• Capture short segments of content.
  Consider the screens that you intend to capture. Users often have better retention of short segments of task-oriented content rather than longer product overviews. Ideally, your content will be 5 minutes or less in length.

Encoding Content

• Use single-pass VBR to encode content from other sources.
  If you are using Windows Media Encoder to encode an uncompressed .avi file, choose one-pass VBR video with a quality level of 93 or higher.
• Use the highest bit rate possible for your deployment scenario and content.
  After you determine your target bit rate, review the total bit rate on the Compression tab in Windows Media Encoder. The encoder adds an overhead value to the audio and video bit rates, so the total bit rate number will actually be higher that the combination of the audio and video bit rates. Therefore, you may need to adjust the audio and video bit rates in order to meet your target bit rate.
  If your audio content is speech-only, and it is recorded under good conditions, an audio bit rate of 4 or 5 Kbps can be acceptable. If the recording also contains other sounds, noises, or music, a higher audio bit rate may be necessary.
• Set the output frame size to the same value as the source.
  Do not use Windows Media Encoder to resize the source video. Doing so will severely degrade the image quality and may make text illegible.
• Increase the buffer size.
  You may want to set the buffer to a higher value, such as 10,000 milliseconds. A larger buffer can accommodate a better image quality, but the user must wait longer for the video to start, as a player waits to play until its buffer is filled.
• Increase the key frame rate.
  You can potentially increase the maximum number of seconds between key frames because there is often less movement between screen frames than with traditional video. For example, often nothing changes between screens for 10 seconds or more except movement of the cursor. A key frame has much more data in it than the average I-frame. Therefore, processing more key frames than you need for your content may decrease the quality.
  Increasing the number of seconds between key frames means that less data is required to create an image over a period of time. This setting depends on the type of screen captures you are doing, so test the setting to determine the key frame rate that works best for your content. You may want to experiment with key frame rate settings of 6, 10, and even 20 seconds. Also note that the Windows Media Screen codec automatically inserts a key frame at each scene change regardless of the key frame rate setting.
• Set Windows Media Encoder to run in 256-color mode.
  To further improve the CPU usage, you can set the Encoder to run in 256-color mode. To do so, right-click the executable file, click Properties, click the Compatibility tab, and then select the Run in 256 colors check box.
  Keep in mind that running in 256 colors can introduce a palette change when switching between programs that have different color schemes. The Encoder does not support palette changes for real-time screen capture. Therefore, you should use 16-bit colors or capture to an .avi file first, and then use the Encoder to convert the file to Windows Media Format.

Back to Top

Recommended Configuration

Back to Top

Playback Considerations

Back to Top

For More Information

Back to Top