Information Technology Reference
In-Depth Information
The composition of MPEG-4 coding is shown in Fig. 33.
2
C
(
u
)
C
(
v
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y
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x
1
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y
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cos
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2
N
2
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D
B
8
㬍
8 block DCT
Error
tolerance
tools
X
A
Y
DCT/
Quant.
Macroblock
Inv.Quant./
IDCT
Intra prediction
Quantized
coefficients
Entropy
coding
㪇
Reference picture
MC
Motion
information
Intra / Inter
(
㶎
)
24
8
2
1
0
0
0
0
6
0
0
0
0
0
0
0
16
4
0
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0
0
0
0
0
1
0
0
0
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2 3
16
Zero-run
Non-zero value
Last
Motion
prediction
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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0
0
0
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0
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½-pel, ¼-pel MC
Unrestricted MC
䋴
MV
3D
VLC
(
㶎
) “Foreman” (MPEG standard image)
Fig. 33
MPEG-4 Visual coding
3.3.3 AVC/H.264
The AVC/H.264 standard is specified as MPEG-4 Part 10 by ISO/IEC as well as
Recommendation H.264 by ITU-T. The improvement in coding efficiency is taken
into consideration as the top priority when AVC/H.264 standardization was per-
formed. It has been reported that AVC/H.264 has the twice as much compression
efficiency of MPEG-2. In AVC/H.264, a multi-directional prediction in the spatial
domain (pixel domain) is adopted as Intra Frame Prediction in order to reduce the
amount of video information. Several prediction methods are defined for lumi-
nance and chrominance signals; 16x16 and 4x4 intra predictions for luminance are
introduced below. Intra 16x16 prediction for luminance is a method which
chooses either of four prediction modes shown in Fig. 34 per macroblock to pre-
dict a 16x16 pixel macroblock.
On the other hand, Intra 4x4 prediction for luminance divides a 16x16 pixel
macroblock into 16 blocks which consist of 4x4-pixel blocks and chooses one of
nine prediction modes as shown in Fig. 35 per block.
Moreover, an adaptive block size partition is adopted for Motion Compensated
Prediction of AVC/H.264. Since seven block size partitions including 16x16, 16x8,
8x16, 8x8, 8x4, 4x8, and 4x4 are defined for Motion Compensation “Prediction, the
size of prediction can be chosen per macroblock (16x16) or subblock (8x8). In addi-
tion, subblock partitioning can be used for four 8x8 blocks independently.
