NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
- 1046 -
Revision V1.30
NUC97
0
T
E
CHNIC
A
L
RE
F
E
RE
N
CE
MA
NUA
L
complete, the JPEG engine will issue an interrupt to host. The status register DYUVMODE reports the
image color format (4:4:4, 4:2:2, 4:2:0, or 4:1:1) that has been decoded. The register JDECWH reports
the original width & height of the decoded JPEG image. The register JPRIWH should be written the
real size image width & height after scaling or not for packet format. The programmer can also get the
quantization-table of the decoded JPEG bit-stream by reading the registers JQTAB0~JQTAB2. For
RGB555 packet output, set ORDER (JITCR[14]) to 1 in the register JITCR.
For 4:4:4 color format images, if the original width is not multiple-of-8, the decoded image will be
padded to multiple-of-8. For 4:2:2 and 4:2:0 color format images, if the original width is not multiple-of-
16, the decoded image will be padded to multiple-of-16. For 4:1:1 color format images, if the original
width is not multiple-of-32, the decoded image will be padded to multiple-of-32.
The JPEG decoder supports the programmable Huffman-table function and can decode the bitstream
that is coded by the user-defined Huffman-table. The programmer can choose to turn-on the
programmable Huffman-table function or directly use the default Huffman-table to decode the JPEG
bitstream by setting the register bit PDHTAB (JITCR[0]).
The JPEG decoder supports 1/2, 1/4 and 1/8 planar format down-scaling in horizontal and vertical
direction to adjust the decoded image size. The programmer can specify the register JPSCALD for
image planar format down-scaling function. The JPEG decoder also supports 1~16X arbitrarily packet
format down-scaling in horizontal and vertical direction. For planar format down-scaling mode, the
programmer needs to specify the down-scale ratio by registers JUPRAT.
The JPEG decoder supports specified window decode mode. This function allows user to specify a
sub-window region within the whole image to be decoded as shown in the following figure. Only the
specified window region image will be decoded and stored to frame memory. This function can be
enabled by setting register bit WIN_DEC (JMCR[6]), and the window region can be specified in
registers JWINDEC0~JWINDEC2.
Planar YUV
bit-stream
DRAM
full image in bit-stream
window region
to be decoded
Figure 5.29-6 Specified window decode mode
When the “header decode complete wait” bit DHEND (JITCR[5]) is set, JPEG will enter the pending
state after the header information has been decoded, and will resume the decode operation after the
interrupt status is cleared.