Extra Information

Chapter 10: MPEG-4 Options and Settings
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Tab Description
— AAC (Advanced Audio Coding)
A standardized, lossy compression and encoding scheme for digital audio.
AAC achieves better audio quality than MP3, a Motion Picture Experts
Group (MPEG) standard.
— AMR (Adaptive Multi-Rate)
An audio data compression scheme optimized for speech coding.
3GPP adopted AMR as the standard speech codec; it is widely used in GSM.
You can either AMR narrow band (AMR-NB) or AMR wide band (AMR-
WB).
NOTE: When you select AMR Encoder for audio, the audio automatically
encodes using 8 kHz mono for playback on cell phones.
Figure 137. MPEG-4 Audio Encoder Options
• The Audio Typesetting (Figure 138) only relates to AAC Encoding.
• If you select AMR in the Encoder field, the system does not use this setting.
• The Audio Type field provides a drop-down box with two choices:
— Low Complexity (LC)
The simplest and most widely used and supported AAC audio format
— Main Profile (MAIN)
The same format as LC (above) with an added backward prediction.
NOTE: Depending on the player where you intend to hear the resulting stream,
either choice uses a specific set of tools to encode the audio stream.
You should make your choice based on the requirement of the playback
software or device.
The most widely supported format is LC profile.