A method and an apparatus to encode a series of quantized coefficients of
a transform of a block of image data. The method includes forming modes
for each encountered non-zero amplitude and forming events for the modes
in the mode-modified series formed by setting to zero all non-zero
amplitudes other than the amplitude defining the mode. An event for modes
for amplitudes greater than 1 is a run of none or more zero-valued
coefficients followed a non-zero amplitude in the mode-modified series. A
first mode is defined for amplitude 1 wherein an event is a run of none
or more zero-valued coefficients followed the amplitude 1 coefficient in
the mode-modified series. In another embodiment, a first mode is defined
for amplitude 1 wherein an event is a run in the mode-modified series of
none or more zero-valued coefficients followed by a run of one of a
predefined set of sequences, each sequence in the set being a sequence of
l's and 0's starting with a coefficient of amplitude 1.