Contents

Introduction

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Capturing Quality Content

• Capturing to an AVI File. For the best quality, avoid combining the capturing and encoding processes. Instead, capture to an AVI file first, and then encode.
• Comparing Audio and Video Sources. Keep in mind that some audio and video sources are better than others. For the best quality, capture SDI video and digital audio.
• Setting Proper Audio and Video Levels. Set your video and audio levels properly before you start capturing.
• Optimizing Your Computer. Check that your computer is optimized.
• Capturing to Optimal Pixel Formats. Capture to a YUY2 pixel format to avoid color conversions during encoding.
• Capturing Optimal Resolutions. Capture video at either a resolution of 320×480 or 640×480.

Capturing to an AVI File

• Removes any issues related to the processor falling behind the capture process, and enables the encoder to optimize all calculations.
• Enables the use of editing programs to perform steps such as trimming the start and end times of the file, or doing color correction.
• Simplifies batch encoding when you source from an AVI file.

• Requires additional steps to capture and encode.
• Involves higher system storage requirements.

Comparing Audio and Video Sources

• Serial digital interface (SDI) video. Used for digital video cameras and camcorders. Because the content stays in a digital format throughout the capturing and encoding processes, this results in the least amount of data translations, and results in the best-quality video.
• Component video. Used when sourcing from DVDs. With this source, the video signals are separated, for example, into the RGB or Y/R-y/B-y format. Results in good-quality video.
• S-Video. Used for S-VHS, DVD, or Hi-8 camcorders. The video signal is divided into luminance and chrominance. Results in good-quality video.
• DV video. Used with DV devices, such as MiniDV digital camcorders connected through an IEEE 1394 video port. Results in good-quality video.
• Composite video. Used for analog cameras, camcorders, cable TV, and VCRs. Composite video should only be used as a source as a last resort. With composite video, luminance and chrominance components are mixed, which makes it difficult to get good-quality video.
• Audio. If possible, capture digital audio. If you must capture audio from an analog source, balanced audio connections are better than RCA.

Setting Proper Audio and Video Levels

• Adjust your video monitor using SMPTE color bars, and then adjust your computer monitor to match, using a high-resolution bitmap of the SMPTE bars.
• Adjust your video capture card levels (hue, saturation, and brightness), so that the picture matches the video monitor.
• Check and normalize all audio levels in your system. Use a professional-grade audio card, such as the Echo Layla24 or the M-Audio Delta Series.
• If possible, use a digital waveform monitor.

Optimizing Your Computer

• Defragment your hard disk.
• Turn off network and file sharing.
• Close all other programs, especially if a program accesses the hard disk.
• Monitor system resources, making sure that the computer is sufficiently powerful to keep pace with the data feed.
• During the capture, watch for frame dropping. It should be possible to capture an entire movie with no dropped frames.
• Watch for direct memory access (DMA) buffer conflicts between the capture card and the SCSI card, which can result in frame dropping. This is less likely to occur now than in the past. If conflicts occur, one solution is to use a dual PCI bus motherboard configuration, in which the capture card and the SCSI card are on different buses.

Capturing to Optimal Pixel Formats

Capturing Optimal Resolutions

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Encoding Techniques

• Optimizing Video
• Preserving Nonsquare Pixel Output
• Selecting an Encoding Mode
• Compression Settings

Optimizing Video

• Film-originated content. Standard motion picture film is shot at 24 frames per second (fps). Before it can be broadcast on television, it must be converted to videotape and put through a telecine process where frames are added that convert it to the 29.97 fps required by the NTSC standard. It is recommended that you apply the inverse telecine filter to remove the extra frames added during the telecine process. This removes redundant data and improves the quality of the encoded video.
• Video-originated content. It is recommended that you either deinterlace or maintain the interlacing in the source video, depending on the playback device you are targeting. Deinterlace for playback on progressive-scan devices such as computers, but maintain interlacing for playback on interlaced devices such as televisions. If you deinterlace the video, Windows Media Player 9 Series or later can detect whether the computer's graphic card supports hardware deinterlacing during playback. If it does, the codec will pass all of the information to the card for deinterlacing. If the graphic card does not support hardware deinterlacing, then deinterlacing is handled by the codec.
• Mixed film and video content. If the source video is 640×480 and 30 fps, deinterlacing is recommended. The encoded video will still have the telecined frames, but interlacing artifacts are removed. Or, you can maintain the interlacing.

Preserving Nonsquare Pixel Output

Selecting an Encoding Mode

• One-pass CBR. Use when capturing live content, when broadcasting, or when you are targeting older players or devices.
• Two-pass CBR. Use when capturing from files, when encoding to a file, and when you want to set up an on-demand streaming scenario.
• Quality-based VBR (one-pass). Use when you want to ensure a constant quality level, for example, when you are archiving content. Maintains consistent quality throughout; spikes bit rate arbitrarily to maintain quality.
• Bit rate-based VBR (two-pass). Use when you want to achieve the best-quality level while staying within a predictable average bandwidth. Use this mode when you are planning to create files that can be downloaded before being played, or when you want to control the size of the output file.
• Peak bit rate-based VBR (two-pass). Use when you want to create content that will be played back on a device that has a constrained reading speed, such as a CD or DVD player. Similar to bit rate-based VBR encoding, except that you also specify the peak bit rate.

Compression Settings

• Key frame. A key frame is a point in encoded video where the data for the entire frame is transmitted, rather than just the changes. Key frames are generally inserted when there is a scene change; they are also inserted at regular intervals to improve seeking. The key frame setting is the minimum time between points where the encoder will insert key frames (they may be inserted more often automatically, if necessary). Decreasing the distance between key frames can improve the quality of the video, but also significantly impacts the overall file size. If you plan to edit the encoded video, reduce the distance between key frames to improve edit quality. If you want to minimize the file size, increase the key frame value, for example, to 20 seconds. If you use a longer key frame distance, additional key frames are inserted when necessary; for example, when a scene changes. Keep in mind, though, that a long key frame distance will affect both the ability to seek within the video and the amount of time a user may need to wait for video in a multicast scenario.
• Buffer size. The bit rate and quality of content fluctuate within the confines of the buffer size. A larger buffer size enables more bits within the buffer range to be allocated to complex scenes. For example, if you set the buffer size to 10 seconds, the codec may choose to allocate x number of bytes to the first 8 seconds, and the rest during the last 2 seconds. This allows for the more complex parts of the video to have more bits allocated within the buffer. Typically, increasing the buffer will improve overall quality. However, it also increases the delay between the time when the user requests the content, and playing starts. For download-and-play scenarios, increasing the buffer size has little impact on this delay. For lower bit rates, it is recommended to increase the buffer size. For higher bit rates, increasing the buffer size has a smaller impact on quality.
• Video smoothness. Video smoothness determines the tradeoff between sharp images and smooth motion. Video appears smooth when objects move easily from one position to another on the screen, and the edges of objects are not jagged. Video appears clear when images and motion are well-defined and clearly delineated. The bit rate setting determines the number of bits that can be allocated over a period of video. Based on this setting, the codec can choose to include more frames, which results in the images appearing smoother because there are more frames. However, each frame uses fewer bits. With a higher video smoothness value, the codec may include fewer frames. This increases the number of bits allocated per frame, resulting in sharper images; however, because there were fewer frames, the image may not appear as smooth. The video smoothness setting only comes into effect when there are not enough bits to encode at the specified frame rate, and a tradeoff must be made. At higher bit rates, this value can be increased. If you are dropping frames during encoding, consider decreasing video smoothness.

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For More Information

• Windows Media Developer Center
• Windows Media Technologies page on the Microsoft Web site
• Windows Media Encoder 9 Series Help on this Microsoft Web page
• Windows Media Technologies and Windows Media Encoder discussion lists

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