在目前复杂的有线和无线网络环境中传输视频信号，带宽问题是最大的瓶颈，如何在低带宽下传输具有一定观看质量的视频信号，视频压缩算法的编码效率成为重中之重，而优秀的MPEG2编码甚至可以达到高级编解码算法的效率。本文是知名编码芯片厂商加拿大VIXS系统公司对编码ASIC设计师的技术建议。

Introduction

Audio and Video codecs (coder/decoder) have always attracted research activity from academia and the industry. These activities are driven by simple economics: better compression means smaller storage and less bandwidth; technical breakthroughs in encoding techniques are enablers of new applications that in turn push new products into the hands of consumers.

For the foreseeable future, moving pictures or Video will always have a significant place in personal entertainment devices -at all layers through the product chain. Furthermore, the major electronics companies will continue to invest in these products and the R&D required to create new products will continue vigorously in the future.

Today, we can view attempts to enable video devices with flash memory and High Definition, or more hours of content with standard DVD media, as further proof that attempts to squeeze more video quality out of fewer bits is still proceeding aggressively.
Even as the price of storage media decreases, it is clear that an average video enthusiast’s home archive is still much higher than commonly available portable flash media today.

Going Digital: Encoding

Today, video or television delivered to the home can be analog ordigital. For the most part, home video content distribution has essentially gone completely digital with DVD-Video accounting for the bulk of the media format. Regardless of the exact date of analog phase out for television, Digital Television is inevitable, and in all cases, companies who are able to provide more efficient encoding methods or solutions for content are going to have a measurable competitive advantage.

MPEG-2 is the pervasive codec for video distribution from DVDs to Digital TV, there are now two new major contenders H.264 (also known as MPEG4-AVC) and Microsoft’s Windows Media 9 (of which VC1 is the current name).

There are various video encoding standards, of which MPEG-2 will be the main focus of this paper.

The next major video distribution format is HD-DVD and/or Blu-Ray, and the content will move towards HD resolutions of 1920x1080i.

Besides MPEG2, both AVC and VC1 are deployed in HD-DVD and Blu-Ray Disk (BD)

This paper will concentrate on several main ideas :

. A brief discussion of determining video quality.
. A discussion on transrating and transcoding.
. A overview of potential pitfalls in concentrating on the simple codec considerations without sufficient attention to the entire video acquisition chain.
. The challenges of building efficient encoders from an algorithmic viewpoint.
. Technical challenges of building efficient encoders from an IC architecture perspective – and a sample solution based on ViXS System’s Xcode Family of ASICs.

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