Autodesk 64006-051108-9001 User Guide - Page 104

Sample Rate, Data Rate, Variable Bitrate VBR, Constant Bitrate, Speed vs. Quality, Normal, Highest

Page 104 highlights

96 Chapter 7: Formats Sample Rate The Sample Rate is the number of audio samples per second that are contained in the final file. Higher sample rates produce better quality audio with correspondingly larger files. The MP3 default sample rate is 44.1 kHz, which is also the sample rate of audio CDs. Other common sample rates for MP3 are 22.050 kHz and 11.025 kHz for lower bitrate files (below 64 kbits/sec) and 44.1 kHz for higher bitrates (64 kbits/sec and above). Data Rate The main parameter controlling the quality of the MP3 file is the bitrate. The higher the data rate, the better the sound quality and the larger the final file. A bitrate of 128 kbits/sec is a widely used standard for high-quality MP3 files. Variable Bitrate (VBR) Variable bitrate encoding can decrease the size of MP3 files by using the requested data rate for the hardest sections of the file and lower data rates for easier sections. This maintains the sound quality of the final file, while making it smaller than its constant bitrate counterpart. However, the file size of VBR MP3s can vary greatly depending on the complexity of the original uncompressed file. Check the Variable Bitrate option to enable VBR MP3 encoding. Constant Bitrate Leaving the Variable Bitrate option unchecked creates constant bitrate MP3 files. Constant bitrate MP3s use the same amount of data per second throughout the entire file. Speed vs. Quality This menu controls the trade-off between faster encoding operations and the best sound quality: •Normal - with most material, you should get excellent results with this setting. •Highest - produces the best possible results, but takes longer to encode. This is only necessary with very difficult material. •Fastest - Encodes the fastest of all the options, but you may sacrifice overall sound quality. This is best used if time is a bigger consideration than quality. A few other factors besides the encoding speed pop-up menu also influence the speed of the encoder. Fewer channels encode faster, so a mono output will encode at twice the speed of a stereo output. Higher frequencies also take more time - 22.050 kHz output encodes faster than 44.1 kHz.

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Chapter 7: Formats
96
Sample Rate
The Sample Rate is the number of audio samples per second that are contained in the final file.
Higher sample rates produce better quality audio with correspondingly larger files. The MP3
default sample rate is 44.1 kHz, which is also the sample rate of audio CDs.
Other common sample rates for MP3 are 22.050 kHz and 11.025 kHz for lower bitrate files
(below 64 kbits/sec) and 44.1 kHz for higher bitrates (64 kbits/sec and above).
Data Rate
The main parameter controlling the quality of the MP3 file is the bitrate. The higher the data
rate, the better the sound quality and the larger the final file. A bitrate of 128 kbits/sec is a
widely used standard for high-quality MP3 files.
Variable Bitrate (VBR)
Variable bitrate encoding can decrease the size of MP3 files by using the requested data rate for
the hardest sections of the file and lower data rates for easier sections. This maintains the sound
quality of the final file, while making it smaller than its constant bitrate counterpart. However,
the file size of VBR MP3s can vary greatly depending on the complexity of the original
uncompressed file.
Check the Variable Bitrate option to enable VBR MP3 encoding.
Constant Bitrate
Leaving the Variable Bitrate option unchecked creates constant bitrate MP3 files. Constant
bitrate MP3s use the same amount of data per second throughout the entire file.
Speed vs. Quality
This menu controls the trade-off between faster encoding operations and the best sound
quality:
Normal
— with most material, you should get excellent results with this setting.
Highest
— produces the best possible results, but takes longer to encode. This is only
necessary with very difficult material.
Fastest
— Encodes the fastest of all the options, but you may sacrifice overall sound quality.
This is best used if time is a bigger consideration than quality.
A few other factors besides the encoding speed pop-up menu also influence the speed of the
encoder. Fewer channels encode faster, so a mono output will encode at twice the speed of a
stereo output. Higher frequencies also take more time — 22.050 kHz output encodes faster than
44.1 kHz.