Video settings

Use the following descriptions as guidelines for understanding the default video profile settings, and also guidelines for customizing those settings. As indicated, some settings are specific to Constant Bit Rate (CBR) or Variable Bit Rate peak (VBR peak constrained) encoding modes. To see some of these settings, you may have to click the Show/Hide advanced properties button .

• Video (check box)   Select this box to encode video.

• Video (menu)   Specifies the compression format and optimal playback scenario of the profile. Select the format that best matches your expected delivery method, or select Source profile to bypass encoding the video and retain the existing compression method. The VC-1 format represents most of the available compression formats. VC-1 creates high-quality encoded video at bit rates that may range from very low to very high. The VC-1 encoding format is considered a standard for professional broadcast and delivery and, additionally, is optimized for Silverlight playback scenarios. You can also choose other Windows Media Video (WMV) encoding formats, all optimized for other streaming scenarios.

• Frame Rate   Specifies the number of frames per second (fps) in the encoded file. Choose a frame rate from the list, or click Source if you want to retain the frame rate in the source footage. The frame rate you choose depends on whether you are encoding high-motion or low-motion video. High-motion video generally looks smoother if you use a higher frame rate, but a higher frame rate increases the amount of work the processor must perform. The setting you specify represents the maximum fps. Depending on factors such as the video size and codec quality setting, the actual fps you achieve might be lower.

• Key frame interval   Specifies the number of seconds between key frames. Key frames display the whole image, while the interval frames, or delta frames, only contain the differences between two key frames, and therefore are smaller. If you increase the time between key frames, the file size decreases. If you decrease the time between key frames, the file size increases. Enter a high interval for content with a static background. Enter a low interval for high-motion content, such as a sporting event.

• Profile   Specifies the type of codec used for encoding. All the profiles in the list create high-quality video for both streaming and downloading, and they all comply with the VC-1 standard. The Simple and Main profiles support a wide range of bit rates, and also two-pass and variable bit rate (VBR) encoding. (See Constant, variable, and multiple bit rate encoding for information about encoding methods and multiple-pass encoding). You should use Main profile to create content for playback on such devices as Zune and use Simple profile is used for playback on mobile devices. The Advanced profile, in addition to supporting the same features as the other two profiles, also supports interlaced content, and is transport-independent. Because this profile supports interlaced content, the codec does not first have to de-interlace the content before compressing it, thereby preserving quality. By using the transport independence feature, you can deliver video over systems that are not Windows Media–based, such as standards-based broadcast, wireless infrastructures, and DVDs.

• Mode   Specifies whether Microsoft Expression Media uses Constant Bit Rate (CBR) or Variable Bit Rate (VBR) encoding. The subsequent profile options that you have to choose from depend on the mode you choose here.

• Buffer window (CBR only)   Specifies, in seconds, the amount of content that you want to preload before playing back. Typically, the delay that occurs as the buffer loads matches the length of the buffer size value. However, if you plan to stream from a Windows Media server, you can take advantage of a feature in Windows Media Services, called Fast Start, which enables a player to fill its buffer faster than real time, assuming that there is sufficient bandwidth. In this scenario, you can set a larger buffer size. For more information about Fast Start, see Windows Media Services Help.

• Peak buffer window (VBR peak constrained only)   Specifies, in seconds, the maximum amount of content that you want the client to preload before playing back. If you are encoding for playback on a hardware device, type the peak buffer size that corresponds to the buffer size on that device.

• **Stream 1   **Specifies the stream. For Multiple Bit Rate (MBR) encoding, additional streams are added by clicking Add at the bottom of the dialog box.

• Width/Height   Specifies the dimensions that you want for the encoded file. Note that increasing the dimensions of a video image may cause distortion. To avoid distortion, either decrease the image size or keep the image at its source size.

• Bitrate (CBR only)   Specifies, in kilobits per second (Kbps) the bit rate of the file. Higher values create larger files and higher quality, but also require more bandwidth for streaming.

• Bitrate (average) (VBR peak and unconstrained only)   Specifies, in kilobits per second, the average bit rate that you want the stream to have. Actual bit rates will vary over the course of the encoded stream, depending on the range of complexity in the content, but the average rate will meet this figure.

• Quality (Quality VBR only)   Sets the bitrate based on a quality scale from 1 to 100.

• Peak bit rate (VBR peak constrained only)   Specifies, in kilobits per second, the maximum bit rate that the encoded stream will reach at any time during encoding. While encoding, Expression Media maximizes the image quality without exceeding this rate. If you are encoding for playback on a hardware device, such as a DVD player, type the reading speed of the hardware device.