4K smart camera based on UVC protocol

Abstract: This paper designs a 4K smart camera based on UVC protocol. The main control adopts Rockchip RV1126 and the sensor adopts SmartSens SC8238. The camera is directly connected to the TV via USB interface to achieve 4K high-definition presentation. It supports UVC protocol and has pedestrian tracking function.

0 Introduction

With the popularity of 4K TVs and the demand for home video conferencing, home entertainment and fitness, this paper develops a 4K smart camera based on the UVC (USB Video Class) protocol. By directly connecting to a 4K TV via a USB cable, end-to-end 4K ultra-clear presentation can be achieved from camera to TV, as shown in Figure 1.

Figure 1 Camera application system block diagram

The 4K smart camera based on UVC protocol developed in this paper is simple to operate, easy to carry, cheap, and has good application and development prospects. This paper focuses on the development of the main circuit of the camera hardware and the implementation of UVC protocol.

1 Hardware Design

The system main control uses Rockchip RV1126, and the sensor uses SmartSens SC8238. The camera collects image information through the sensor and transmits the collected image information to the main control through the MIPI signal. The main control encodes and decodes the image and sends the image information to the TV through the USB interface. The TV displays the image information collected by the sensor, thus realizing 4K ultra-clear presentation from the camera to the TV. The camera video signal flow is shown in Figure 2.

1.1 RV1126 Introduction

RV1126 supports 4K (3 840×2 160) H.265 30 fps video encoding, quad-core Arm Cortex-A7 architecture, and integrates 2.0 Tops NPU. NPU supports INT8/INT16 mixed operations and can easily switch between TensorFlow, MXNet, PyTorch, and Caffe. Each core of RV1126 contains a 32 KB I-cache, 32 KB D-cache, and a shared L2 cache of 512 KB. The chip content integrates HDR (High Dynamic Range Imaging), 3A functions (AE, AF, AWB), LSC, 3DNR, 2DNR, sharpening, dehaze, fisheye correction, gamma correction, feature point detection and other algorithm accelerators. The chip integrates MIPI (Mobile Industry Processor Interface) interface and is directly connected to the sensor through MIPI signal.

1.2 SC8238 Introduction

SmartSens SC8238 supports a maximum transfer rate of 4K (3 840×2 160) and is an industry-leading digital CMOS (Complementary Metal Oxide Semiconductor) image sensor that outputs raw format images with an effective pixel count of 3 872×2 180 and can read and write registers through a standard I2C (Inter-Integrated Circuit) interface. It uses 1.5 μm back-illuminated pixel technology and has the lowest power consumption among similar products at a sensitivity of 1 160 mV/Lux·s.

1.3 Hardware Design

The hardware circuit mainly includes power module, clock reset circuit, main control, sensor, USB (Universal Serial Bus), DDR (Double Data Rate) and Flash, etc. The hardware circuit block diagram is shown in Figure 3.

The power of the whole system is provided by USB, the clock and reset ensure the normal operation of the system, Flash is used to store programs, DDR is a random access memory, the system collects image data through SmartSens sensor chip SC8238, encodes and decodes the image data with Rockchip RV1126 chip, and finally sends the image data to the TV through USB2.0.

The RV1126 clock circuit consists of an internal feedback circuit and an external 24 MHz crystal oscillator circuit; when the system clock uses an active crystal, the clock amplitude is 1.8 V±10%. The chip resets when the chip reset pin is low for more than 4 μs. A 100 nF capacitor is placed in parallel with the chip reset pin to enhance the anti-interference ability of RV1126 and prevent false triggering from causing system reset. DDR adopts a T-type design. The DQ and DQS bidirectional signals can be directly connected. A 49.9 Ω termination resistor is connected in series at the end of the differential clock signal. The spacing between different signal lines in the DDR4 group and the spacing between two adjacent signal lines between groups must use the "3W" principle; the single-line characteristic impedance is controlled at 50 Ω±10%, and the differential pair impedance is controlled at 100 Ω±10%. The PLL power supply includes PLL_AVDD_0V8 and PLL_AVDD_1V8, which must be powered separately and placed close to the corresponding pins with a coupling capacitor. This can improve the stability of the system when DDR works at high frequency. The core power supply voltage is 0.8 V, and a separate DC-DC power supply must be used, and the power supply capacity must not be less than 1 A. The NPU power supply voltage is 0.8 V, and a separate DC-DC power supply must be used, and the power supply capacity must not be less than 2 A. The chip USB controller uses a 200 Ω reference resistor with an accuracy of 1%. This resistor affects the quality of the USB eye diagram. Since this design uses USB to transmit video streams, this resistor is very critical; an electrostatic protection device must be placed on each USB signal line, and the parasitic capacitance of the device must not be greater than 1 pF. The device should be as close to the USB as possible during ESD PCB layout.

SmartSens sensor chip SC8238 includes three power supplies: DOVDD (1.8 V), AVDD (2.8 V) and DVDD (1.2 V). The filter capacitor must be placed close to the pin; at 4K frame rate, DVDD must be designed to be 1.2 V. The chip's VREFN, VREFN2, VREFH and TXVDD are connected to the ground through capacitors, which can filter out the high-frequency and low-frequency parts of the power ripple. The MIPI signal differential line impedance is controlled at 100 Ω, with an error of less than ±10%; MIPI signals cannot be routed straight, otherwise signal reflection will occur, affecting the high-speed video transmission performance, and there must be a complete ground reference layer under the MIPI signal, which cannot be split.

2 UVC Protocol

UVC is short for USB Video Class, which is a protocol standard jointly launched by Microsoft and other manufacturers for USB video capture devices. UVC devices include a video control interface (VC Interface) and a video stream interface (VS Interface); the video control interface is mainly used for configuration operations to allow UVC devices to enter different functional states, and the video stream interface is responsible for the video data stream transmission of UVC devices. The topology of UVC includes video stream input/output, camera video stream transmission control, switching and selection control of image data acquisition sources, and processing of image-related parameters.

3 Conclusion

The 4K smart camera based on UVC protocol designed in this paper can be directly connected to the TV through the USB interface to give users a perfect 4K ultra-high-definition presentation. This camera is easy to use, economical, and has good video effects. It can be widely used in home video conferencing and home entertainment and fitness.

References:

[1] N KHALID, GOCHOO M, JALAL A, et al. Modeling twoperson segmentation and locomotion for stereoscopic action identification: A sustainable video surveillance system[J]. Sustainability, 2021,13.

[2] SJURSEN AD, FRIIS M, RNNING L, et al. Monitoring of anadromous salmonids in the fjrevassdraget watercourse, Nordland[C]. Results from the video surveillance in 2020- 2021.

[3] MOSAIF A, RAKRAK S. A new system for real-time video surveillance in smart cities based on wireless visual sensor networks and fog computing[J]. Journal of Communications, 2021, 16(5):175-184.

[4] SHAHBAZ A, JO K H. Dual camera-based supervised foreground detection for low-end video surveillance systems[J]. IEEE Sensors Journal, 2021,PP(99):1-3.

[5] SEVCIK J. A special peripheral component interconnect express card for video surveillance systems in alarm applications[J]. Przeglad Elektrotechniczny, 2021, 1(5):30- 35.

[6] PANDAS K, SAHU S K. Design of IoT-based real-time video surveillance system using raspberry Pi and sensor Network[M].2021.

[7] HUANG H, SAVKIN AV, NI W. Online UAV trajectory planning for covert video surveillance of mobile targets[J]. IEEE Transactions on Automation Science and Engineering, 2021, PP(99):1-12.

[8] KUMAR P. Development of a thermal-visible video surveillance system based on fractional order tvmodel[J]. Journal of Physics Conference Series, 2021, 1950(1):012026.

[9] ISAEVA O, BORONENKO M, BORONENKO Y. Making decisions in intelligent video surveillance systems based on modeling the pupillary response of a person[C]. 2021 IEEE 6th International Conference on Computer and Communication Systems (ICCCS). IEEE, 2021.

[10] ZHANG J, JIA X, J Hu, et al. Moving vehicle detection for remote sensing video surveillance with nonstationary satellite platform[J]. IEEE Transactions on Pattern Analysis and Machine Intelligence[J].2021,PP(99): 1-1.