Google tackles VP8 video quality question

Some believe Google's new Web video technology doesn't match the existing H.264 in quality. Google is offering some rebuttal.

Google has begun answering concerns that VP8, the compression technology it hopes will invigorate and liberate Web video, isn't as good as a rival.

Which is better at compressing video, H.264 or VP8? Some sites such as Quavlive offer comparisons.
Which is better at compressing video, H.264 or VP8? Some sites such as Quavlive offer comparisons. Screenshot of Quavlive by Stephen Shankland/CNET

Nobody questions that VP8 is superior to Theora, the encoding-decoding "codec" that also has been available without royalties. But some have concluded that it's not as good as H.264, aka AVC, today's dominant but definitely not royalty-free codec.

VP8, combined with the Vorbis audio codec, form the guts of the open-source, royalty-free WebM project Google launched two weeks ago. Google attracted many allies for the project, but it's got some more convincing to do, too.

StreamingMedia.com's Jan Ozer posted one VP8 vs. H.264 comparison. "In higher motion videos...H.264 seems superior," he said, then concluded, "I'd say H.264 still offers better quality, but the difference wouldn't be noticeable in most applications."

A stronger criticism came from Jason Garrett-Glaser, a developer of the x264 encoder for H.264 video. In his VP8 technical analysis, he said, "Overall, VP8 appears to be significantly weaker than H.264 compression-wise." He also criticized the maturity of the specification itself.

But VP8 is new technology, and Google already has begun trying to teach people more about its inner workings on the WebM project blog.

Take one of Garret-Glaser's big concerns. "The lack of B-frames in VP8 is a killer," he said, referring to a technique to cut down on data transfer burdens by sending instructions on how to reconstruct a frame of video based on the preceding and following frames. It's a technique used to cope with limited data-transfer rates and processing power in a decoder.

Google had a specific response, though.

"The lack of B frames in VP8 has sparked some discussion about its ability to achieve competitive compression efficiency. VP8 encoders, however, can make intelligent use of the golden reference and the alternate reference frames to compensate for this," said Google codec engineer Yaowu Xu in the blog post that details some of the technology. He also pointed interested parties to the WebM project's detailed descriptions of VP8 parameters that can be used when encoding video.

Another set of still-frame comparisons can be found at Quavlive, a company developing streaming-video server software.

 

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