Appeal No. 2003-2092
Application 09/046,285
Appellants’ specification. The figure is a block diagram of an
MPEG encoder. See page 6 of Appellants’ specification. With
prior art MPEG encoders, each 8 x 8 block of coefficients is
encoded by the VLE unit 34 and sent to the compressed output
interface as part of the encoded bitstream. Each encoded
coefficient is variable in length. The variable-length code is
selected based on the value of a given quantized DCT coefficient
and its distance from the previous non-zero coefficient in the
block as determined by a predefined block scanning order.
Therefore, the actual encoded size of an 8 x 8 block, in terms of
number of bits, is unknown until after each coefficient’s
variable-length code has been determined within the VLE unit.
See pages 8 and 9 of Appellants’ specification. In accordance
with Appellants’ invention, a digital video picture is encoded to
an exact size by calculating and setting a bit limit per block in
the VLE unit 34. As represented by block 50, the VLE unit 34
accumulates a sum of the total number of bits per block while
receiving the quantized DCT coefficient as input and outputting
of the variable length code. The VLE unit represented by block
52 compares the accumulated number of used bits with the block
limit value set by the microcode, and the VLE terminates its
output of variable-length code for a given block when the
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