Apple Compressor 2 - Manual (Page 170)

170 Chapter 12 Creating QuickTime Movie Output Files
The Sound Settings dialog contains the following items, with various choices for each,
depending on the audio codec you choose in the Format pop-up menu.
 Format: Choose the audio codec you want to add to your setting.
 Channels: Choose the type of channel output, such as mono, stereo, or some type of
multi-channel output, depending on the codec.
 Rate: Choose the sample rate you want to use for your media file. The higher the
sample rate, the higher the audio quality, but the larger the file. Downloading a
larger file takes longer and requires more bandwidth.
 Options: This button remains dimmed unless the codec you selected from the
Format pop-up menu offers options. It is recommended that you contact the
manufacturers of these codecs directly for more information about the additional
options they offer.
QuickTime Audio Sample Sizes and Rates
If you have the disk space and bandwidth, it is best to leave your audio uncompressed.
Uncompressed audio normally uses 8-bit (phone quality) or 16-bit (CD quality) samples.
Compressor 2 supports up to 64 bits per sample floating point and a maximum sample
rate of 192 kHz.
Choosing an Audio Codec
AAC is a good general purpose audio delivery codec and it is compatible with a wide
variety of playback devices. For low-bandwidth audio on faster computers, the
QDesign Music codec (QDMC) is good for most material, while Qualcomm PureVoice is
the best choice for speech-only material. For slower computers, CD-ROM, and kiosk
situations, IMA is a better choice, because it is less computer intensive, thus allowing
the computer to focus on the more challenging video stream. See “
QuickTime Audio
Codecs ” on page 175 for more information about audio codecs.