Sound
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.
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
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.
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.
W760r/VA76r Media Guide | Page 33 |