95 What's this Macroblock stuffing, dammit ?: (MPEG-2)
Description
This article is from the MPEG FAQ, by Frank Gadegast phade@cs.tu-berlin.de with numerous contributions by others.
95 What's this Macroblock stuffing, dammit ?: (MPEG-2)
A genuine pain for VLSI implementations, macroblock stuffing was
included in MPEG-1 to maintain smoother, constant bitrate control for
encoders. However, with normalized complexity/activity measures and
buffer management performed a priori (before coding of the macroblock,
for example) and local monitoring of coded data buffer levels now a
common operation in encoders, (e.g. MPEG-2 encoder Test Model), the
need for such localized bitrate smoothing evaporated. Stuffing can be
achieved through slice start code padding if required. A good rule of
thumb is: if you find often yourself wishing for stuffing more than
once per slice, you probably don't have a very good rate control
algorithm. Nonetheless, to avoid any temptation, macroblock stuffing
is now illegal in MPEG-2 (A general syntax restriction brought to you
by the Implementation Studies Subgroup!)
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