RM0082
LS_JPEG codec
Doc ID 018672 Rev 1
563/844
.
●
Vi
This value defines the vertical sampling factor for the color component I; value can
range from 1 to 4.
●
Hi
This value defines the horizontal sampling factor for the color component I; value can
range from 1 to 4.
●
Nblocki
Number of data units (i.e. 8 x 8 blocks of data) of the color component I contained in a
MCU, minus 1. The range of possible values for Nblocki is 0-15, because 4 bits are set
aside for this field. However, it is important to note that according to the ISO
specification, in the case of the baseline algorithm, the following relation must hold:
●
QTi
This value defines the quantization table to be used for the color component i. Since
four quantization tables are possible, 2 bits are sufficient for this field.
●
HAi
This value defines the Huffman table to be used for the encoding of the AC coefficients
in the data units belonging to the color component i. Since only two AC tables are
allowed in the baseline algorithm, 1 bit is sufficient for this field.
●
HDi
This value defines the Huffman table to be used for the encoding of the DC coefficients
in the data units belonging to the color component i. Since only two DC tables are
allowed in the baseline algorithm, 1 bit is sufficient for this field.
25.4.8
JPGC control status register
This register contains the status of the codec controller. The bit 0 (interrupt bit) is
automatically set when a coding process has finished.
Table 477.
JPGCreg4-7 register bit assignments
Bit
Name
Reset
Value
Description
[31:16]
Reserved
-
[15:12]
-
Vertical sampling factor for component
i
.
[11:08]
-
Horizontal sampling factor for component
i.
[07:04]
-
Number of data units of the component
I
contained in a MCU,
minus 1.
[03:02]
-
Quantization table used for component
i.
[01]
-
AC Huffman table used for component
i
.
[00]
-
DC Huffman table used for component
i.
Σ
Nf
i
0
Nblocki
1
+
(
)
=
10
≤