Ministry of Innovation / Business of Technology

Google submits VP8 bitstream to IETF, but not as a standard

Google is working to have the VP8 video codec specification published by IETF …

Earlier this month, Google submitted a document describing the bitstream specification for its VP8 video compression algorithm for publication by the Internet Engineering Task Force (IETF). This isn't a step towards standardization, says Google, but a step towards creating a definitive reference for the technology.

IETF publishes Request For Comment (RFC) memoranda, used to describe various technologies used on the Internet. RFCs include IPv4, the Internet Protocol, SMTP, used for e-mail, and many others besides.

VP8 is the video codec used in Google's WebM specification, a royalty-free technology that Google has proposed for providing video over the web. The codec was developed by codec company On2, which Google bought last year.

The bitstream defines the structure of the final compressed data; in conjunction with a description of how to convert that encoded data into usable video, you have a complete description of the compression algorithm. The encoding process—how to turn video into that bitstream in the first place—is typically left unspecified: any process that produces a bitstream that conforms with the specification is acceptable as an encoder. This approach gives developers the ability to develop their own quality-enhancing optimizations even many years after the bitstream specification is published, while ensuring that the resultant file can still be played back by any compliant decoder.

The current draft was submitted on January 6. As it stands, the draft is not an authoritative description of the codec: it acknowledges that there may be discrepancies between the draft and the reference source code published by Google. If such discrepancies are found, the document states that Google's source is definitive and overrides the specification. Elsewhere, the specification relies on snippets of C source code rather than describing the structures and algorithms used.

This kind of issue would stand in the way of any eventual standardization should Google seek to go that route in the future, but indicates that the company is interested in providing a better specification that allows implementers to support VP8 without having to make reference to thousands of lines of source.

For the time being, however, the company has not indicated any intent to go the standards route with VP8. According to CNET, the company says that this move is "independent from a standards track": rather, it is to ensure that there is a "canonical public reference" for the document.

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