
What DV standards call
level
is
the magnitude (i.e., absolute
value) of the AC coefficient.
Sign is coded separately.
When a DV VCR is in shuttle mode, it is quite likely
that a single CAA will be recovered individually, without
any of the other four CAAs of its segment. Overflow data
for the macroblock is quite likely to be missing.
However, overflow data is limited to high-frequency AC
coefficients. In shuttle playback, missing overflow coef-
ficients are replaced by zero. This causes loss of picture
detail in the reconstructed picture; however, the
absence of these coefficients