[M4IF Technotes] What's low complexity about AAC LC

[Ivan Dimkovic]

Ben,
> Ivan,
>
>     Spot on, thanks.
>
>     Given that the quality difference is so slight, why prediction anyway?
>

Prediction has some advantages on certain types of signals - Signals that
have strong tonal character are easy to predict, but this is not the case
with many natural signals. However, if the maximum possible quality is
required then the prediction is useful. There are some other problems with
prediction as well, backward adaptive prediction (used in Main profile) has
very long sequences of frames and each frame needs all frames after the last
prediction reset. That could be very tricky in wireless/internet real-time
communication (signal could become distorted if some of the frames with
prediction data is missing), and it also makes seeking very tricky. This is
one reason more not to use prediction for many applications. Portable
devices also use LC profile because their decoding circuits need to be as
cheap as possible.
Regards,
*************************************************
Ivan Dimkovic, Technical Manager
PsyTEL Research
Multimedia Coding Solutions
Belgrade Yugoslavia
phone:  +381 64 11 40 600
fax:    +381 11 32 25 275
email:  dim   psytel-research.co.yu
www:  http://www.psytel-research.co.yu
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