
Philips Semiconductors
PNX15xx Series
Volume 1 of 1
Chapter 21: MPEG-1 and MPEG-2 Variable Length Decoder
PNX15XX_SER_3
Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Product data sheet
Rev. 3 — 17 March 2006
21-12
MPEG-1 Parsing
For each MPEG-1 macroblock parsed by the VLD, four 32-bit words of macroblock
header information will be output from the VLD. Refer to
Figure 1.
The elds described in
Figure 3 may or may not be valid depending upon the MPEG-
1 video standard. See
Table 7 for more details on the macroblock header data
MV Field Sel[0]0] to
MV Field Sel[1][1]
Undened
Section 6.2.5 and 6.2.5.2
Motion Code[0][0][0] to
Motion Code[1][1][1]
Undened
Section 6.2.5.2.1 and Table B-10
Motion Residual[0][0][0]
to Motion
Residual[1][1][1]
Undened
Section 6.2.5.2.1; the corresponding rsize bits are extracted from the bitstream
and stored as left justied; to get the nal value shift the given number by (8 -
corresponding rsize). The rsize values are stored in MP_VLD_PI register
Start Code
-
dmvector[1] and
dmvector[0]
Undened
Section 6.2.5.2.1 and Table B-11; signed 2-bit integer from Table B11.
CBP
-
Section 6.2.5, 6.2.5.3 and Table B-9
Quant Scale
-
Section 6.2.5; 5 bits from bitstream; use Table 7-6 to compute the quant scale
value.
Table 6: References for the MPEG-2 Macroblock Header Data …Continued
Item
Default Value
References from MPEG-2 Video Standard, IS 13818-2 Document
Figure 3:
MPEG-1 Macro Block Header Output Format
Esc Count
MBA Inc
MB Type
Motion Code [0][0][1]
Motion Residual [0][0][0]
Motion Residual [0][0][1]
Motion Code [0][0][0]
Motion Code [0][1][1]
Motion Residual [0][1][0]
Motion Residual [0][1][1]
Motion Code [0][1][0]
quant scale
CBP
31
First Forward Motion Vector
First Backward Motion Vector
0
1
2
3
4
6
11
17
25
7
15
23
29
30
31
13
7
15
23
29
30
31
13
4
10
12
14
31
w1
w2
w3
w0
MB1
MB2
First MB
slice_start_code
23
16
Shaded areas represent bits not implemented in the MPEG-1 specification.
These bits are written as zeros.