The H.264 Basics

You hear a lot about H.264, especially in conjunction with HTML5 video, but are you sure you know what it means? To help you get a basic understanding of this video standard, we spoke to Abhik Majumdar, the technical lead for the video transcoding team at Ooyala. Majumdar was happy to sort through some simple questions so that you'll know exactly what people mean when they talk about H.264.

What is H.264?
While some might disagree, says Majumdar, it's the best overall video compression standard for a wide range of applications.

Is it a format or a codec?
It's a codec. It often gets treated like a format, since it's compared to WebM, a format used in HTML5 video. Keep in mind that a video format is a container file that holds a video codec and an audio codec. WebM uses the VP8 video codec. When H.264 is used in HTML5 video, it's part of an MP4 container, so MP4 is the format. The audio codec is AAC. (We're simplifying this a bit. There are variations. For example, you'd use the MPEG TS format to stream live video to an Apple iOS device, and that format also uses the H.264 video codec).

What software can view H.264?
H.264 video is widely supported, says Majumdar. On Macs and Apple mobile devices, QuickTime can decode it. On Windows systems, the Windows Media Player can handle it, if you have the correct plug-in. Flash and Silverlight players can both work with it. Internet Explorer 9 will support it, and Microsoft will offer a plug-in to add H.264 support to the Chrome browser (it's already done so for Firefox). Apple's Safari browser supports it.

Why are we hearing so much about H.264?
Google has been pushing the VP8 codec, since it's license-free. Microsoft and Apple both side with H.264. Both are license holders for the codec (they're members of the MPEG-LA H.264 licensing pool), although both pay more in fees to the pool then they get in profits.

Should video content owners be concerned with H.264 compatibility?
There's a lot of fragmentation in the market now, says Majumdar, because of the HTML5 turf battles. If you're streaming on the Web, H.264 files can work with Flash and Silverlight players, even on Chrome browsers with the right plug-in. He also notes that a good online video platform (OVP), such as his employer Ooyala, will help reduce the confusion of making sure your videos play on a wide variety of platforms.

How does H.264 quality compare to WebM?
"That's a very fraught questions," Majumdar says with a laugh, before choosing to pass on this one. We can tell you, though, that most experts, including our own Jan Ozer, find H.264 slightly superior in video quality.

How does a content owner start using H.264?
There are several software or hardware encoders around, such as x264 which is open source; commercial tools from Sonic, DivX, and others; and hardware tools from companies like Inlet. QuickTime can do it. Alternatively, you could choose an OVP or online encoding service that does the work for you.

Troy Dreier's article first appeared on OnlineVideo.net