Conexant CX25853多路视频参考设计

Conexant 公司的CX25850/1/3是多路视频译码器,包括了特别适合于视频监测市场的快速锁定和小信号锁定特性. CX25850 和 CX25851集成了4个模拟视频译码器,每个译码器有高性能的10位ADC,可单独缩放.整个译码器是全10位数据通路. CX25853集成了8个相同质量的译码器和16个复合视频输入. CX25850/1/3还包括两个模拟视频编码器和一个数字监视器输出,并支持BT.656数字视频接口, 而CX25851还支持同步象素接口(SPI)数字视频接口.本文介绍了CX25850/1/3的主要特性,方框图以及采用CX25851/3和Maxim公司MG3500的8/16路PCIe捕捉卡参考设计方框图.

Multi-Channel Video Decoder CX25850/1/3

High Quality Integrated Video Surveillance System Front-End

The CX25850/1/3 multi-channel video decoder devices contain fast locking and low signal locking features designed specifically for the video surveillance market. The CX25850 and CX25851 both integrate four analog video decoders, each with a high-performance 10-bit ADC, full 10-bit data path through the decoder, and independent scaling. Eight composite video inputs allow the user to multiplex between two cameras on each video decoder input. The CX25853 integrates eight of the same high quality decoders and sixteen composite video inputs. The CX25850/1/3 also contains two analog video encoders and a digital monitor output port. All three devices support BT.656 digital video interfaces. The CX25851 also supports Synchronous Pixel Interface (SPI) digital video interfaces. All devices are designed for PC-based and embedded/stand-alone security Digital Video Recorders (DVRs).

Flexible Architecture

With two composite input ports per decoder, the CX25850/1 supports direct connections for eight cameras, and the CX25853 supports sixteen cameras.

This eliminates the need for external video multiplexers in systems where two cameras share a video decoder. Additionally, the CX25850/1/3 contains two on-board, high quality analog video encoders with dedicated BT.656 input pins.

Alternatively, these encoders may be driven by streams internal to the device. These encoders provide surveillance DVR manufacturers with a convenient way of driving external monitors. When connected to the monitor output port, the CX25850/1/3 offers users the opportunity to “scroll” between decoder outputs at fixed intervals and/or switch to view a specific decoder output.

Ease of Use

The CX25850/1/3 requires minimal programming for startup using an I2C serial protocol. The devices are preconfigured in a default mode for development, verification, and fast prototyping. The fast locking and low signal locking features were developed and  optimized specifically for the video surveillance market. Fast locking ensures that each decoder within the CX25850/1/3 will lock to a new/switched input within one field, a feature that is useful in multiplexed camera systems. Low signal locking ensures that each decoder within the CX25850/1/3 will lock to composite signals as low as 100 mV

peak-to-peak, a feature that helps in systems where cameras and feeds are not perfectly terminated.

Integrated Filters

All video inputs have integrated anti-alias filters, eliminating the need for external filter components. These filters help improve the video decoding process by removing aliasing artifacts prior to the digitization process.

Conexant employs a proprietary method of luma-chroma separation of the composite video sources to ensure optimum video quality.

Distinguishing Features

Integrated NTSC/PAL video decoding and encoding

10-bit ADCs and DACs

Analog composite video interfaces

Multiple video decoders with 2 analog composite inputs per decoder

Fast locking (<1 field) and low signal locking (100mVp-p)

Independent scaling on each video decoder path

BT.656/VIP digital interfaces

Dedicated monitor output programmable to switch between decoder paths and/or

cascade multiple devices together

Integrated anti-alias filters

On-chip voltage regulator

20mm X 20mm eTQFP package and 13mm x 13mm fpBGA package (CX25850)

28mm X 28mm eLQFP package (CX25851)

28mm X 28mm eLQFP package and 19mm x 19mm fpBGA package (CX25853)



图1.CX25850/1/3方框图

基于Conexant CX25851/3和Maxim MG3500的视频解决方案

Solution based on Conexant’s CX25853, CX25821, and Maxim’s MG3500

Conexant Systems and Maxim Integrated Products have jointly developed this PCIe-based reference design for PC-based video surveillance products with Digital Video Recording (DVR) capabilities. The reference design enables a complete solution for video surveillance DVR applications and provides up to 16 channels of H.264 compression at D1 resolution. This comprehensive hardware and software design platform gives video surveillance product manufacturers a powerful, cost-effective solution to quickly deliver products to market.

The solution is made possible with Conexant’s CX25853 Multi-Channel Video Decoder, CX25821 PCI-Express Media Bridge, Maxim’s MG3500 HD H.264 Video Codec, and Lattice FPGAs.

Conexant’s CX25853 is the world’s first eight-channel video decoder. The chip enables multiple analog video streams to be captured and compressed simultaneously. The decoder features a high-performance 10-bit ADC, full 10-bit data path through the decoder, independent scaling, two analog video encoders, and digital monitor output port. The decoder supports BT.656/VIP digital video interfaces and provides high-quality eight-channel integrated NTSC/PAL decoding with 5-line comb filtering. Key features include the capability to lock to low-level video signals, horizontal and vertical scaling, and hue, brightness, saturation, and contrast controls. The chip’s high-density architecture lowers per-channel decoder costs by as much as 35 percent, and substantially reduces board space requirements compared to using two separate four-channel devices. This reference design uses two CX25853 devices to provide up to 16 channels of real-time video decoding.

Media bridging is handled with Conexant’s companion CX25821 device, which enables multi-channel, bi-directional digital audio and video transfers to a host computer via an integrated PCIe interface. The CX25821 bridges both uncompressed (from CX25853) and compressed (from Maxim MG3500) data in this design. The dual-path architecture allows system designers to optimize PC-DVR system architecture and resources. The uncompressed data may be used for real-time monitoring and/or video analytics, while the compressed data may be sent directly for storage and retrieved independently for playback.

Video compression is performed by Maxim’s MG3500 H.264 Video Codec, a highly integrated, low-power System-on-Chip (SoC), which increases recording capacity on DVRs. Each MG3500 supports up to four channels of low-latency full D1 video compression. Key technical capabilities include digital image stabilization, motion detection, object tracking, scene change detection, privacy region protection, and digital time stamps. The SoC performs de-interlacing, scaling, and tiling to produce high quality images with flexible displays and resolutions. This reference design also includes Lattice FPGAs, which perform key video format conversions.

The combination of the CX25853, CX25821 and MG3500 SoCs provide video surveillance product manufacturers with the perfect solution for PC-based DVR video surveillance applications and advanced security networks that require hardware-based compression.



图2.解决方案外形图

Distinguishing Features

Complete solution for real-time video surveillance DVRs

Low price per channel

Small PCB area

Integrated NTSC/PAL video decoding and encoding

Up to 16 channels of hardware-based H.264 compression and bridging to PCIe

Up to 16 channels of uncompressed video bridging to PCIe

PCIe 1.1 compliant

High quality images with flexible displays and resolutions

Windows and Linux drivers

Quick time to market

Conexant CX25853

Integrated eight-channel video decoder: Low price per channel and small PCB area

5-line comb filter: Excellent luma/chroma separation for best image quality and compression efficiency

Low-signal locking: Fewer amplifiers required in overall system Conexant CX25821

Multiple channels of BT.656 and I2S bridging to PCIe:

More cost-effective than Field-Programmable Gate Arrays (FPGAs)

MG3500 host-interface: Allows bridging of H.264 compressed data to PCIe

Windows and Linux drivers

Maxim MG3500

Multi-channel H.264 compression, up to four channels per device: Low price per channel and small PCB area

De-interlacing, scaling, and tiling: High quality images with flexible displays and resolutions

Compressed and Uncompressed outputs: Separate paths for recording and monitoring



图3.采用CX25851/3和MG3500的8/16路PCIe捕捉卡参考设计方框图