This article is from the MPEG FAQ, by Frank Gadegast phade@cs.tu-berlin.de with numerous contributions by others.
A . Despite the fact that a comprehensive worldwide standard now exists
for digital video, many areas remain wide open for research: advanced
encoding and pre-processing, motion estimation, macroblock decision
models, rate control and buffer management in editing environments,
implementation complexity reduction, etc. Many areas have yet to be
solved ... (and discovered)..
 
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