Selecting audio and video codecs
Select the compression algorithms (codecs) that you want to apply to your audio and video content and specify a bandwidth for the annotation stream.
- Audio codec. Select the audio codec. By default, Microsoft Windows Media Audio codec version 7is selected because, in most cases, it produces the best sound quality. However, if you are creating a low-bandwidth stream (less than 20 Kbps) that has voice-only audio content, you may obtain better results by using the low-bitrate Sipro Labs ACELP codec. If you are creating an uncompressed profile, Pulse Code Modulation (PCM) is the only option available. PCM is used to capture high-quality audio, but results in large file sizes.
- Audio format. Select the quality level that you want to apply to the audio stream. A higher sample rate yields higher-quality audio, but requires more bandwidth. Ideally, you want to achieve the right balance between bit rate and sampling rate. Remember that the audio stream must share the available network bandwidth with any video or script streams.
- Video codec. Select the video codec. For most encoding scenarios, you should use the Microsoft Windows Media Video version 7.0 codec. If you are targeting an audience that uses Windows Media Player version 6.4, select the Microsoft MPEG-4 version 3.0 codec. If you are encoding content produced by many consumer electronics devices, such as digital video cameras and cell phones, select ISO MPEG-4 video codec version 1.0. For capturing screens, select the Windows Media Screen codec.
- Video size. This setting determines the size of the video window that users view in Windows Media Player. Select Same as source when capturing screens, which is only available if Microsoft Windows Media Screen codec is selected, to ensure that the size of the encoded screen matches the original. Quarter Common Interface Format (QCIF) and Common Interface Format (CIF) are predefined image standards that are supported by many codecs and video editing tools. CIF height and width are twice those of QCIF. The 160 x 120 and 320 x 240 options provide video sizes that are slightly smaller than QCIF and CIF, respectively. The slight decrease in size means that more bandwidth can be used for video frames and can improve quality in some scenarios. Use these options if video sharpness is more important than video size for your content. The 640 x 480 option provides the highest-quality video, but it also generates the largest bandwidth requirement. Use Custom to define a custom size. Video size should be between 32 and 1600.
- Advanced. Click Advanced to set a variable compression buffer size. The variable compression buffer is the amount of time that content is stored before encoding begins. A larger buffer results in better quality content, but requires more memory. When you encode content, the encoding process will be delayed by the amount of time specified in the buffer. The content will be delayed by the same amount of time when loaded into Windows Media Player. When streaming a live event, the content played in Windows Media Player runs behind the live event by the amount of time that you specify in the variable compression buffer.
- Scripts. Type the bit rate that you want to use for scripts. The script bit rate consumes a portion of the bandwidth shared with the audio and video streams. Valid bit rates are between 1000 and 9999.
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