Motorola VA76R ユーザーズマニュアル
Sound
W760r/VA76r Media Guide
Page 33
MP3 Audio Guidelines
MP3 (MPEG Audio Layer 3) is an audio compression technology that is part of the MPEG-1 and MPEG-2
specifications. Developed in Germany in 1991 by the Fraunhofer Institute, MP3 uses perceptual audio
coding to compress CD-quality sound by a factor of 12, while providing almost the same fidelity. Because
MP3 audio is digitized, not synthesized, reproduction (disregarding speaker quality) is identical on all
devices. Therefore MP3 ring tones provide a near-CD quality audio experience for listeners as opposed
to their MIDI counterparts that differ greatly from device to device.
specifications. Developed in Germany in 1991 by the Fraunhofer Institute, MP3 uses perceptual audio
coding to compress CD-quality sound by a factor of 12, while providing almost the same fidelity. Because
MP3 audio is digitized, not synthesized, reproduction (disregarding speaker quality) is identical on all
devices. Therefore MP3 ring tones provide a near-CD quality audio experience for listeners as opposed
to their MIDI counterparts that differ greatly from device to device.
The following recommendations should be used when designing MP3 audio clips for use in the phone.
Technical Specifications for MP3:
• Bit Rate: 64kbps recommended
• Recommended file size: 30kb
• Maximum duration (NW dependent): 16-30 secs
• Recommended file size: 30kb
• Maximum duration (NW dependent): 16-30 secs
Available Sound Properties
Follow technical specifications outlined above.
Design Guidelines
Since ring tones need to be at a consistent audible level, compressing the original content to reduce the
peak-to-average ratio is necessary. After the audio is compressed, it is advisable to re-normalize the
audio to 0db before saving the compressed MP3 file.
peak-to-average ratio is necessary. After the audio is compressed, it is advisable to re-normalize the
audio to 0db before saving the compressed MP3 file.
NOTE:
Ring tones are generally between 15-20 seconds in length. Based on the recommended bit
rates, that duration would yield a file size of 75-150K per ring tone. It is advisable to keep file size less
than 100K to allow the end-user to download multiple tones, but file size is limited only by the total
free memory available on the device.
than 100K to allow the end-user to download multiple tones, but file size is limited only by the total
free memory available on the device.