Image Processing Reference
In-Depth Information
Try to avoid sourcing 3GPP material from already compressed, Web-based content.
Noisy VHS tapes are also a bad source format, and anything that's been produced for TV
consumption must be looked at carefully because it is probably not ideal for mobile devices.
When streaming to GRPS, 3G, and dial-up modems, use Frame Skip
Probability—this sets the priority to sustain the bit rate, sacrificing the frame
rate in return.
When encoding content for use on mobile devices whose screens are very small, consider
the following points:
Compose the shots so the picture is framed tightly on the action.
Avoid cuts between scenes.
Use large, clear text.
Make the packages short.
Use mono audio.
Pre-emphasize the audio for small speaker size.
Gamma-correct video for the display characteristics.
Typical size for packages used to be 90 KB, but this has increased to 300 KB now that the
networks can transfer downloads more quickly.
Encoding Formats
Encoding formats for 3GPP include H.263, AMR, MPEG-4 Simple Profile—Level 0, and
AAC audio. Make sure to check on the kind of packetizing that the network requires.
For 3GPP2, H.263 is okay with audio in QCELP format. AMR, MPEG-4 Simple
Profile—Level 0, and AAC are also fine.
Also check out the Kinoma codec and player. They have been designed with mobile
applications in mind, although they are aimed more at PDA users than mobile phone
3GPP Versus 3GPP2
The differences between the two 3G file formats are subtle and are best shown in a tabu-
lar form. Table 28-1 enumerates the various properties of both standards.
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