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The Moving Picture: Concerning Codecs
Posted Nov 30, 2007 Print Version     Page 1of 1

As videographers, we really don’t have to be experts in streaming, though online distribution plays an ever-increasing role in the video we produce, how we show and deliver it, and how our clients share it. Streaming used to be a two-horse race—Windows Media and Real Video—but the streaming world has changed so much in the last few months that you need a scorecard to keep track of the players. Consider this your scorecard.

Let’s start with MPEG-4/H.264/AVC. Back in early 2004, I penned a column called MPEG-4 is Dead. With several years in the rearview mirror, I can confidently say that I was right, and wrong, and right, and wrong. This is not a misprint, but recognition that MPEG-4 is many things, including a vision, a container format for audio and video, and several video codecs, some of which have succeeded, some of which haven’t.

MPEG-4 is a well-defined standard that has realized significant success and has great momentum. The standard has many "parts," including Part 2 for the MPEG video codec, Part 3 for the Advanced Audio Coding (AAC) audio codec, Part 10 for the Advanced Video Coding (AVC) codec, and Part 14 for a container format or "wrapper" for all of the above. MPEG-4 the codec (Part 2), which was the actual focus of my 2004 column, failed because video quality never approached the quality that Microsoft or Real offered. Few, if any, websites ever streamed MPEG-4 video, and even QuickTime-based movie trailers generally favored the Sorenson Video 3 codec over MPEG-4.

However, MPEG-4 the video codec was supplanted by the AVC codec (MPEG-4 Part 10), which delivered near visual parity with Real and Windows Media, and is the first video codec supported by the International Telecommunication Union (ITU) and the International Organization for Standardization (ISO). The ITU called the standard H.264, while the ISO dubbed it AVC. Blatantly ignoring the wisdom of my column, Apple subsequently made MPEG-4 and AVC the only two supported video codecs for the iPod. More recently, when Adobe announced that it would support MPEG-4/AVC playback in Flash, it cemented AVC’s importance in the streaming space. More on that in a moment.

Interestingly, since MPEG-4 Part 14 was largely based on Apple’s QuickTime, the two formats are kind of joined at the hip. With most encoding tools, you can create a QuickTime (.MOV) or MPEG-4 (.MP4) file with the MPEG-4/AVC video codec and AAC audio codec. Most players, including QuickTime and the iPod, will play files with either extension interchangeably, though MOVs seem more prevalent for streaming and desktop playback and MP4s more widely used for devices.

For the most part, the MPEG-4 video codec (Part 2) is "dead," since the AVC/H.264 codec (Part 10) is superior in almost every application. The sole exceptions are low-powered devices like the iPhone or iPod, though all versions of the iPod can play AVC files. For most video produced for streaming, progressive download, or desktop playback, AVC is preferred. Let’s turn our attention to Flash. Flash video appeared on the radar using the Sorenson Spark codec, but it achieved prominence with the introduction of On2’s VP6 codec, which delivered quality on par with Real, Windows Media, and AVC. However, since Flash video uses MP3 audio compression, it trailed behind the quality offered by Real and Windows Media. In addition, since VP6 was a proprietary codec, it lacked hardware support for real-time encoding or the compression acceleration that is enjoyed by standards like MPEG-4.

By incorporating MPEG-4 files into Flash, Adobe resolved both issues, getting access to more powerful encoding and boosting compressed audio quality. The forthcoming update to the Flash player will play MP4 and MOV files containing MPEG-4 audio and video codecs. Most producers will wait until the new player has been widely disseminated to start using MPEG-4 formats.

Finally, there’s Microsoft, which made two major codec-related announcements in 2007. The first was that SMPTE adopted Windows Media Video (WMV) 9 as a standard, calling it VC-1. VC-1 first appeared as a mandatory video standard in HD DVD and Blu-ray players (along with H.264 and MPEG-4), though few authoring tools support it. The second announcement was Silverlight, an architecture and development environment that competes with Flash. This player war will rage for the next few years. Silverlight allows WMV producers to create a customized, branded skin for their videos, much like you can do with Flash. Silverlight is also a much smaller Mac/Windows plug-in than the Windows Media Player; it has greater compatibility in the Mac environment.

Silverlight is not a codec upgrade, however, and it uses the same WMV/VC-1 codec as before, so it doesn’t deliver better video quality. Still, its new look and Mac compatibility are compelling, and if you’re currently producing Windows Media—given all the viable choices currently available—you should download a trial version of the Expression Encoder to see the new look.

Jan Ozer is a frequent contributor to industry magazines and websites on digital video-related topics and the author of DV 101: A Hands-On Guide for Business, Government & Educators, published by Peachpit Press.

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