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Recommendation H.261
(03/93)
9
T1 5142 30-93/ d0 5
PSC
T R
PT YPE
PSPA RE
PE I
PEI
GOB data
FIGURE 5/H.261
Structure of picture layer
FIGURE 5/H.261...[D05] = 3 CM
4.2.2
Group of blocks layer
Each picture is divided into groups of blocks (GOBs). A group of blocks (GOB) comprises one twelfth of the CIF or one
third of the QCIF picture areas (see Figure 6). A GOB relates to 176 pels by 48 lines of Y and the spatially corresponding 88
pels by 24 lines of each of CB and CR.
Data for each group of blocks consists of a GOB header followed by data for macroblocks. The structure is shown in Figure
7. Each GOB header is transmitted once between picture start codes in the CIF or QCIF sequence numbered in Figure 6, even
if no macroblock data is present in that GOB.
12
1
34
3
56
5
7
8
QCIF
910
11
12
CIF
FIGURE 6/H.261
Arrangement of GOBs in a picture
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