Technology for high-efficiency encoding (encoding/decoding) of video continues to progress. At NAB2005, the video technology show held in Las Vegas from April 16 to 19, 2005 there were a number of new coding technologies presented. The major entry was H.264/Moving Picture Coding Experts Group Phase 4 Advanced Video Coding (MPEG-4 AVC), or just H.264 for short. Broadcasting, communications and next-generation optical discs using the new coding technology are expected to enter mainstream commercial use in 2005 as development accelerates.
Competition is focused on the compression ratio, in two different areas of processing: non-realtime processing, intended for use in on-demand video distribution; and realtime processing, for relay and similar applications. According to Bob Wilson, chairman and CEO of Modulus Video, Inc of the US, a firm developing H.264-compliant high-efficiency encoding technology, "Carriers want to pump three or four programs through a single communication line into the home at once, and want at least one of them to be HDTV." The higher the compression ratio, the more channels it becomes possible to cram into a given capacity.
1080p via ADSL
NTT Cyberspace Laboratories of Japan offered one of the highest compression ratios for non-realtime processing. By investing about 10,000 times the duration of the original video they can pack a 1080/60p image, the high-definition television (HDTV) format with the most data, small enough to run at 1.8Mbps (Fig a). While it takes 1,600 hours or more to encode a 10-minute video clip, once it is compressed it becomes possible to distribute HDTV imagery through asynchronous digital subscriber line (ADSL) or wireless services running at only a few Mbps.
The technology encodes the same video clip several dozen times, determining the optimal parameters and boosting precision. Parameters include things like encoding mode and quantization characteristics.
At the show, engineers offered a comparison with the quality standard image joint model (JM) developed by the International Standards Organization (ISO) and International Telecommunication Union (ITU). The NTT Cyberspace technique took about ten times as long as the JM source code, but the result offered about the same image quality at only two-thirds the size. Researchers say their next target is to hit half the encoding data rate of JM, or about 1.3Mbps.
1080i at 5.5Mbps
In realtime processing, the ME6000 H.264-compliant encoding system from Modulus showed a high compression ratio, achieving a bit-rate of 5.5Mbps for a 1080i HDTV signal (Fig b).
The ME6000 consists of a microprocessor and three field programmable gate arrays (FPGA). The FPGAs handle processing such as image scaling, inter-frame prediction and motion prediction. FPGA internal pipelining minimizes the number of external memory accesses required, contributing to lower encoding times.
Even though H.264 has left the lab, existing broadcast services will continue using MPEG-2 for some time to come, and Media Excel, Inc of the US interprets this as an opportunity. The firm demonstrated its transcoding utility, capable of converting MPEG-2 HDTV imagery into H.264 SDTV imagery in real time.
The transcoding system from Media Excel operates six TMS320DM642 digital signal processors (DSP) in parallel, directly converting MPEG-2 HDTV into H.264 SDTV image streams, according to the company. The DSPs require an operation frequency of about 20MHz to handle conversion to SDTV, as compared with over 1GHz for HDTV.
by Takahiro Kikuchi
(July 2005 Issue, Nikkei Electronics Asia)
Nikkei Electronics |
Nikkei Monozukuri |
Nikkei Automotive Technology |
|---|---|---|
 |
 |
 |
| The magazine for electronics designers and managers. | Design You Won't Regret - How to Reduce the Risk of Accidents | The comprehensive automotive technology magazine. |
Copyright © 1995-2010 Nikkei Business Publications, Inc. All rights reserved.
All editorial content and graphics on this Web site may not be reproduced in whole or in part without the express permission of the copyright owner.
