Windows媒体 Is Alive and Well
In 2008, 微软 finally got off the “our encoder is best” bandwagon and announced support for H.264 in Silverlight at the International Broadcasting Convention in Amsterdam. 多年来, Windows媒体 and 微软 had been the enemy of any standards body or industry group, such as the Internet 流媒体 Alliance or the MPEG Industry Forum. 现在他们将成为朋友. H.264 is today as important to 微软 as Windows媒体 was a few years ago—maybe more so, since the primary responsibility for codecs was moved from the server group (Windows) to the tools group (Visual Studio, 表达式).
就在大约一年之前, 微软 had taken its codec to SMPTE as a proposed standard, and after a lot of puts-and-takes, Windows媒体 was approved as SMPTE VC-1. To help market what most people know as Windows媒体, 微软 positioned Windows媒体 as its implementation of the SMPTE VC-1 standard, which is sort of like getting your date pregnant then marveling at how much the baby looks like you.
幕后，AT&T was working on rolling out its U-verse service to consumers. U-verse is a private IP-based network to deliver voice, data, and video to consumers provisioned over an xDSL rather than a radio frequency-based cable system. Designing a system for national rollout takes time, and there are enormous consequences to selecting which codec to put into millions of set-top boxes and what sort of delivery infrastructure you need. 自然, MPEG-2是首选, as it is still the primary codec for conventional digital cable TV systems. But as a new IPTV service where bandwidth might be tight, AT&T同时选择H.264和Windows媒体.
真的? AT&T does not talk much about Windows媒体, and even the Wikipedia post says U-verse is based on H.264. But for the thousands of public, 教育, 还有政府渠道(是的, including your local equivalent of Wayne’s World), 都是Windows媒体, aka VC-1 delivered over a single T1 line from the TV station to AT&T的网络操作系统. Actually, the T1 is a commodity business internet access line that allows AT&T to pull the Windows媒体 stream from the TV station at about 1.5Mbps, which gives an acceptable quality level. AT&T then distributes the stream to local subscribers via IP multicast, which gives them scale. 效果很好.
Many local TV stations cry foul, not because of quality issues, but because AT&T has segregated municipal channels to a special area of its user interface—you have to navigate there rather than finding it through random channel surfing. In other words, it’s more like web streaming than cable TV, or more like Roku. Or Boxee. Or 网飞公司 or Hulu. The under-30 crowd won’t have a problem with this, and there are several benefits. 第一个, in the conventional cable world, a local TV channel would only reach to the edge of the town that the cable franchise served. With U-verse, you can watch any channel within your state, so the potential audience grows. 第二个, because the TV station has an encoder, it typically uses the same technology to simulcast its live content on the public internet. That internet stream is usually in the same format that goes to U-verse: Windows媒体. Thus, your local TV station is viewed on the web via Silverlight or Windows媒体 Player. 多亏了实时转码, those same feeds are often also available via Flash Player; on iOS devices, Android设备, and Blackberries; and on Roku boxes via a live H.264 stream, even though the source originates, as it must, in Windows媒体 Format.
Windows媒体, 如mpeg - 2, 拥有庞大的安装基础, and we won’t see technology updates until the existing equipment and infrastructure are fully depreciated, and then only if there is a business case to do so. 与此同时, Windows媒体 is surprisingly alive and well, and we see new systems going in every month.
This article was originally printed in the April/May 2012 流媒体杂志.
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