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Appendix A | Appendix B | Appendix C | Glossary | Index | Legal Stuff | License


Chapter 20 - The Audio Tab

Audio Codec | Frequency | Depth | Channels | Volume

The Audio tab lets you set the parameters that control the audio in the final output movie, such as the codec, frequency, bit-depth, and more.




Audio Codec

Media Cleaner supports all available audio codecs, which may be selected with the "Codec" pop-up. Your codec choice will substantially change the settings available for a given audio track, because many codecs only work with particular bit depths, channels, etc.

See Appendix B and our WWW site for more tips on selecting audio codecs. As of the ship date of Media Cleaner Pro 2.0, there were not many available other than IMA, but some looked probable for release in mid 1997.

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Frequency

Frequency, or sample rate, is the number of samples per second used for audio. Higher frequencies give higher quality sound, but the resulting audio takes more space. A common choice for CD-ROM content is 11.025 kHz.

If you select a frequency that is different from your original movie, Media Cleaner will resample your soundtrack to the new frequency. Media Cleaner automatically uses a high quality sine-algorithm resampling method. Media Cleaner will not resample audio if your output frequency is identical to your source movie's audio frequency.

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Depth

The depth, or sample size, is the accuracy with which a sound sample is recorded. Media Cleaner supports either 8-bit or 16-bit samples. The latter is more accurate and provides more dynamic range, but takes up more space. Many audio codecs, such as IMA, only work with 16-bit audio.

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Channels

Media Cleaner supports either one channel (mono) or two channel (stereo) sound. Unless the source movie has stereo audio, there is no reason to use the "Stereo" option, as it takes twice the bandwidth of a mono audio track.

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Volume

You can change the volume of your audio track with the "Adjust" slider. Numbers are percentages ­ greater than 100 increases the volume, less than 100 decreases the volume. Zero is silent.

You may select "Normalize" instead of "Adjust." The Normalize feature scans through the movie to find the loudest sound, and then determines the correct volume adjustment to make this sound the maximum volume. This volume adjustment is then applied to the entire movie.

NOTE: Audio Interleave - Media Cleaner automatically handles audio interleave. Under QuickTime 2.1 and later, all flattened movies are automatically set to an interleave of 1 second for the first second, and 1/2 second for the rest of the movie ­ QuickTime will override any other interleave factor, so Media Cleaner defaults to this 1/2 second interleave.

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