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NXP Semiconductors
PNX15xx/952x Series
Volume 1 of 1
Chapter 21: MPEG-1 and MPEG-2 Variable Length Decoder
PNX15XX_PNX952X_SER_N_4
NXP B.V. 2007. All rights reserved.
Product data sheet
Rev. 4.0 — 03 December 2007
21-661
The DCT coefcients associated with the macroblock are output to a separate
memory area. Each DCT coefcient is represented as one 32 bit quantity (16 bits of
run and 16 bits of level). For intra blocks, the DC term is expressed as 16 bits of DC
size and a 16 bit value whose most signicant bits (the number of bits used for DC
level is determined by DC size) represent the DC level. Each block of DCT
coefcients is terminated by a run value of 0xff.
Run-Level Output Data
The DCT coefcients associated with the macroblock are output to a separate
memory area and each DCT coefcient is represented as one 32-bit quantity (16 bits
of run and 16 bits of level). For intra blocks, the DC term is expressed as 16 bits of
size and a 16-bit value whose most signicant bits represent the DC level. The
number of bits used for DC level is determined by the DC size)‘. Each block of DCT
coefcients is terminated by a run value of 0xFF.
3.3.3
Restart the VLD Parsing
The restart of the parsing command at the last decoded symbol position is done
through the use of the VLD_BIT_CNT register to count the number of bits from the
main memory VLD buffer that have been consumed. The VLD_BIT_CNT register can
be initialized to zero by issuing the VLD_INIT command. It counts up when bits are
shifted out of the VLD. This counter wraps around after reaching its maximum value.
3.4 Error Handling
The VLD can generate two types of errors. The VLD_MC_STATUS register has two
VLD error ags.The VLD errors are 1) bitstream parsing error and 2) run-level
overow error. See
Table 8 for details on the VLD error handling procedure.
Table 7: References for the MPEG-1 Macroblock Header Data
Item
Default value
References from IS 11172-2 document
Esc Count
0
Section 2.4.3.6
MBA Inc
-
Section 2.4.3.6
MB Type
Undened
Section 2.4.3.6 and Tables B-2a to B2d
First MB
0
Set to ‘1’ for the rst macroblock of a slice
Motion Code[0][0][0] to
Motion Code[0][1][1]
Undened
Section 2.4.2.7 and Table B-4
Motion Residual[0][0][0]
to Motion
Residual[0][1][1]
Undened
Section 2.4.2.7;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
-
CBP
-
Section 2.4.3.6 and Table B-3
Quant Scale
-
Section 2.4.2.7