ginngi engineering

An embedded video encoder was developed that accepts analog video at its input, and implements a RTP compliant video and audio streaming Ethernet server using H.264 compression and proprietary deinterlacing techniques. In addition a full HTTP server was implemented to provide remote configuration and monitoring using a custom HTTP API library.

Analog video provided by a standard definition camera was fed into the system via a video decoder A/D chip that provided digitized 4:2:0 video. In addition, audio was provided via a standard audio A/D chip. A custom FPGA was developed to perform deinterlacing of the input video to convert it to progressive format which was then compressed using a H.264 core using the baseline standard. The compressed video was then transferred to a Davinci DSP that performed both real-time streaming of the video and audio streams using the RTP standard.

The hardware design consisted of a base board and a processing engine board. The base board provided simple low frequency functions such as physical interfaces, drivers, clocks and power supplies and so its layout was rather simple except for the USB and Ethernet traces that required special care to ensure proper impedance matching.

The processing engine consisted of a mezzanine card that implemented the high speed digital blocks of the system including the Davinci DSP and the Xilinx FPGA. Three DDR memory systems were implemented, one for the FPGA deinterlacer, one for the FPGA based H.264 compressor and one for the Davinci DSP.

Since the width of the mezzanine board was only 1 mm we were limited to ten layers. PCB layout was carefully planned to meet the requirements of each of the blocks. In particular, the DDR memories required both impedance matching, and length matching, clocks were shielded, and cross talk was minimized by separate critical layers with ground planes. Some very critical nets, such as the 480 Mhz USB and the 100Mhz Ethernet were carefully laid out using balanced-shielded techniques.

To reduce the decoupling capacitor requirements a pair of power/ground planes were placed in such a way as to take advantage of their inherent capacitance at the high frequencies.

Creative use of buried and micro vias were used to optimize routing.