HTML and CSS Reference
In-Depth Information
Figure 7-10. The millions+ information in Apple's QuickTime Player
This keying technique knocks out all of the pixels with the color value in question, which is something you see
every day and may not even notice. In fact, did you happen to catch last night's weather report on the news? Well,
chances are that the meteorologist was standing in front of a green-screen and not an actual map. The big thing to
understand here is that this is a huge functional part of video in any medium and, of course, online media. Having
video, interactive or not, overtop a publisher page is a necessity in cutting-edge advertising campaigns. Some of the
most innovative home-screen takeovers have achieved great results by using alpha video.
However, in HTML5 video support, there are currently no cross-browser codecs/wrappers that support the alpha
channel—not H.264, VP8, or even Vorbis. Only VP8 shows promise that it can handle the support in its future, but it's
limited to work in certain browsers, and on top of that, Apple's Safari shows no signs of supporting it, which is a huge
miss in the whole market share on mobile. It's pretty obvious that this is a huge problem and one that will soon be fixed,
but in the interim, designers and developers will need to leverage HTML5's canvas element and write the bitmap data
from the video onto the canvas element during playback and key the pixels there. You can find a really great example
of this at or . While no true
HTML5 video codec supports the alpha information, the effect to the end user is essentially the same; however, keep
performance in mind because you're essentially doubling the load for the browser by combining two elements for
writing the video information to the canvas element. In the interim and until HTML5 video natively supports a codec
that handles the alpha information; you can always fail back to use Flash Player because it has supported this feature
since 2005 with the VP6 codec.
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