基于CX25858设计的8路音视频译码方案

CX25858集成了用作监视的PCIe接口的8路音视频译码器,包括有8路高质量的NTSC/PAL视频译码器和10位ADC以及5路梳状滤波器,可以获得最高质量数字视频输出和尽可能最低噪音. CX25858还包括8路高质量单声道音频A/D和I2S输出.本文介绍了CX25858主要特性,方框图,以及多路音/视频译码器评估板主要特性和方框图.

The CX25858 8-Channel Audio/Video Decoder with Integrated PCIe Interface was designed for surveillance applications. The CX25858 contains eight high quality NTSC/PAL video decoders with 10-bit A/Ds and 5-line comb filtering, to generate the highest quality digital video output with the lowest possible noise. This creates not only the best image quality for viewing, but enables lower bitrates for compression devices using the output of the CX25858.

The video decoders within the CX25858 are optimized to lock to inputs with low signal levels as well as line-locked cameras, both of which are common in surveillance systems. Each video decoder may be scaled independently and the CX25858 supports BT.656 as well as a variety of other interleaved digital video output formats.

The CX25858 also contains eight high-quality mono audio A/Ds with I2S outputs.

CX25858主要特性:

PCIe Bridging

The CX25858 contains a PCIe 1.1 compliant x1 interface. It is ideal for ”capture card” applications in systems where eight channels of high-quality, uncompressed video must be digitized and transmitted via PCIe for viewing, compression, and/or analytics. The CX25858 can downscale digital video from 4:2:2 format to 4:1:1, reducing bandwidth requirements from 16 bits per pixel to 12.

Additionally, the CX25858 supports the bridging of up to four channels of digital video and audio from PCIe, and can output these streams over pins in BT.656 or I2S-style interfaces, respectively.

Direct-Connection to Multi-Channel H.264 CODECs

The CX25858 supports byte, line, or frame-interleaved digital video outputs at 27, 54, or 108 MHz. Byte and line interleaved outputs are supported entirely within the CX25858. Frame-interleaved outputs require that the CX25858 interface with external DDR2 memory. The CX25858 supports I2S and multiplexed I2S audio outputs.

The CX25858 contains an interface for Maxim H.264 CODECs that permit the CX25858 to bridge compressed data from Maxim devices to the PCIe bus.

This simplifies the Bill of Materials (BOM) and reduces costs in PCIe systems.

Distinguishing Features

Eight High-Quality NTSC/PAL video decoders:

- Anti-alias filters

- 10-bit A/Ds

- 5-line comb filtering

- Independent scaling

Eight Mono audio A/Ds

- Variable sample rates

- I2S outputs

Flexible digital video output formats at 27, 54, and 108 MHz

- Byte-interleaved

- Line-interleaved

- Frame-interleaved (requires external DDR2 memory)

PCIe 1.1 x1 interface

Interface to Maxim CODECs for bridging of compressed data to PCIe

Tiling and cascading functions (requires external DDR2 memory)

Programmable Motion Detection

48 GPIO pins

Additional Features

There are two variants of the CX25858 offered ― one with the external DDR2 interface, and one without the interface. When equipped with DDR2, the CX25858 supports frame-interleaved video outputs, as well as a 2x2 CIF tiling mode, in which four CIF
images are tiled into a single D1 stream.

The CX25858 may be cascaded with the CX25838 to create a 16-channel system for sending video and audio data over PCIe. The CX25858 includes programmable motion detection logic, which can trigger flags or PCIe interrupts when motion is detected on incoming analog video streams.

The CX25858 contains 48 GPIO pins, which maximize flexibility and allow customization to a variety of applications and designs. I2C interfaces and the Maxim interface are supported via GPIOs.


图1.CX25858 方框图