STV-974/552S-R01 STMicroelectronics, STV-974/552S-R01 Datasheet - Page 18

• Manufacturer Part Number: STV-974/552S-R01
• Description: KIT DEMO W/VS6552
• Manufacturer: STMicroelectronics

Specifications of STV-974/552S-R01

• Sensor Type: CMOS Imaging, Color (RGB)
• Sensing Range: VGA
• Interface: I²C
• Sensitivity: 30 fps
• Embedded: No
• Utilized Ic / Part: STV0974E, VS6552
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 497-3891

STV0974
4.4.5
4.4.5.1 JPEG markers
4.4.5.2 Runlength and Huffman encoding
Entropy coder
This block performs the following functions:
These markers are compliant with ISO DIS 10918-1 Annex B.
The output JPEG file includes markers defined in
Table 7: JPEG markers included in
Encoding of DC coefficient
The so-called DC coefficient is the first coefficient of each DCT data block. This DC coefficient is
coded through its DPCM difference with its previous value, which is huffman encoded. This is
described in ISO DIS 10918-1 Annex A - Section F.1.2.1. The DC Huffman tables are described in
ISO DIS 10918-1 Annex A - Section K.3.
Figure 10: Encoding of DC coefficient
In the example from
DC coefficient is 12 (DC coefficient of Block Y1). The DPCM value is 4-12 = -8 and the encoded
value will be Huffman (-8). The code that is generated is Code = DC Huffman (-8).
Encoding of AC coefficients
The 63 left coefficients of each DCT block are called AC coefficients. They are encoded using run-
length and Huffman encoder. The run-length encoding consists in counting the number of zero
values between each non-zero coefficient. When a non zero coefficient is found, the Huffman code
of the pair (number of preceding zero, Number value) is Huffman encoded. If a run contains more
than 15 zeros, a specific number called ZRL is Huffman encoded.
If all the values up to the end of the block are equal to zero, a specific code called EOB is Huffman
encoded.
Start of image
Define Quantization Table
Start of frame for baseline DCT
Define Huffman Tables
Start of Scan
End of image
●
●
●
insertion of JPEG Markers
runlength encoding
Huffman encoding
Marker Function
DC
12
1
2
4
Block Y1 data values
Figure 10
16
3
4
77
, the DC coefficient in Block Y2 is equal to 4, the previous Luminance
AC
STV0974
SOI
DQT
SOF
DHT
SOS
End of image
DCT coefficient numbers in zigzag order
0
63
1
output data stream
Name
64
0
Table 7
DC
1
4
, in order of appearance.
2
5
Block Y2 data values
22
3
FFD8
FFDB
FFC0
FFC4
FFDA
FFD9
10
4
Functional description
AC
Value
63
0
64
0
18/61