Appeal No. 96-2696
Application 08/167,415
The quantizing circuit is responsive to the amount of data in
the send buffer (Spec. at 5, lines 7-12).
As shown in appellants' Figures 2(a) to 2(c), each frame
of image data is divided into N slices, each of which contains
M macroblocks (also referred to as macro blocks), each of
which in turn consists of luminance data Y1 to Y4 and color-
difference signal data Cb and Cr (Spec. at 3, lines 13-23).
Appellants' specification explains that prior art systems have
inserted "invalid codes" into the data stream at the
transmitting end in order to prevent an underflow of data:
[S]ince the image data is transmitted as the variable
length code, when a simple stationary image, for example,
continues for a comparatively long[] period, the data to
be transmitted becomes shortage [sic]. In this case, in
view of preventing missing . . . transmission data, an
invalid code can be added to the data to be transmitted.
This invalid code can also be added, for example, in
units of [a] slice or macroblock shown in Figs. 2(a) to
2(c). [Spec. at 13, lines 4-12.]
Examples of such invalid codes are described as follows with
reference to appellants' Figures 3 and 4:
Fig. 3 illustrates an example where an invalid code
(invalid data) is added in units of [a] slice. Each
slice is provided with a slice start code at its leading
area. This slice code is formed by a synchronous code
and an attribute code. The synchronous code is formed by
the data of two bytes where each bit is all [sic] set to
logic 0 and the data of one byte (three bytes in total)
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