PRELIMINARY
S3C6400X RISC MICROPROCESSOR
MULTI-FORMAT VIDEO CODEC
21-46
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
Reordering coefficients
Reordering is performed based on scan types set by the BIT processor. The scan types are listed below.
y
H.264
The H.264 baseline profile uses only the zig-zag scan type.
y
MPEG-4/H.263P3
The MPEG-4/H.263P3 uses 3 scan types zig-zag, alternative horizontal, and alternative vertical scan
type. Which scan type is selected based on the AC/DC prediction flag and macroblock type. In case of inter-
macroblock type, only zig-zag scan type is used. For intra-macroblock, if AC prediction flag is ‘1’, the scan type is
dependent on the prediction direction of DC coefficient. If AC prediction flag is ‘0’, only zig-zag scan type is
applied.
Accessing the coefficient memory
The BIT processor reads or writes coefficient in the coefficient memory by specifying the block index, scan type,
and the corresponding coefficient index. Figure 21.36 illustrates how the BIT processor accesses the coefficient
memory.
―
block index : In case of the MPEG-4/H.263P3, each 8x8 block has its own index in range from 0 to 6.
For the H.264, the range for the block index- the size of block is 4x4- is from -1 to 25. The assignment of
the index is based on the standard.
―
scan type : The BIT processor does not have to consider it should write or read coefficient to which
position of the coefficient memory for both encoding and decoding. The coefficient memory interface
writes or reads coefficients after reordering them based on the specified scan type.
F[0][0]
Coeff[0][0]
Coeff[0][1]
Coeff[0][63]
Coeff[1][0]
Coeff[1][1]
Coeff[0][63]
F[0][1]
F[0][63]
F[1][0]
F[1][1]
F[1][63]
Coeff[5][63]
F[5][63]
0
15
Block Index (0~5)
Coeff. Index(IPB
Address
Bus[7:2]) (0~63)
Address Generator & Reordering
Scan type
Coefficient memory I/F registers
Reordered
coefficient or
concatenated
flags for specified
block
(in case of
encoding)
Decoded
coefficient (in
case of decoding)
IPB read data bus
IPB write data bus
Figure 21.36 Coefficient memory access