LS_JPEG codec
RM0082
568/844
Doc ID 018672 Rev 1
When decoding with header processing, this table is automatically programmed by the
codec core, while in the case of ECS only decoding, the HuffSymb table must be
programmed before starting the codec core.
25.4.19 JPGCDHTmem
memory
Together with the HuffEnc table, this is one of the two Huffman tables required by the codec
core when it acts as an encoder.
As specified in the ISO documentation, in the case of the baseline algorithm, up to two
tables for encoding DC coefficients and two tables for encoding AC coefficients can be used.
the memory map is shown in
The standard specifies that the Huffman table values be 8 bit words and in the following
format:
DC tables and AC tables:
Li
: number of huffman codes of length
i
: this specifies the number of huffman codes for each
of the 16 possible lengths that the specification allows. This represents the first 16 bytes of
each DC table and AC table address block in the JPGCDHTMem memory.
Vi: value associated with each Huffman code: this specifies the value associated with each
Huffman code of length
i
. This
mt
=
L1
+
L2
+ … +
L16
bytes following the 16 length values.
25.4.20 JPGChuffenc
memory
Together with the HuffDHTMem table, this is one of the two Huffman tables required by the
codec core when it acts as an encoder.
As specified in the ISO documentation, in the case of the baseline algorithm, up to two
tables for encoding DC coefficients and two tables for encoding AC coefficients can be used.
the memory map is shown in
162
173
SYMB DC 0 and 1values
174
335
SYMB AC 1 value
Table 487.
JPGC huffsymb memory map (continued)
First address
Last address
Table
Table 488.
JPGCDHTmem memory map
First address
Last address
Table
0
27
DC Huffman table 0
28
205
AC Huffman table 0
206
233
DC Huffman table 1
234
411
AC huffman table 1