Re: [rtcweb] Proposal for H.263 baseline codec

"Kevin P. Fleming" <> Fri, 20 April 2012 21:50 UTC

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Date: Fri, 20 Apr 2012 16:50:39 -0500
From: "Kevin P. Fleming" <>
Organization: Digium, Inc.
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Subject: Re: [rtcweb] Proposal for H.263 baseline codec
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On 04/20/2012 04:19 PM, Gregory Maxwell wrote:
> wrote:
>> On 03/29/2012 09:53 AM, Stephan Wenger wrote:
>>> The other issue, though (the fact that the license grant extends only to
>>> the VP8 implementation as provided by google, and does not extent to
>>> derivative works such as hardware implementations) should be moderately
>> This is concerning, even for us open source software distributors. In
>> fact, a similar situation existed some time ago with iLBC; the license
>> that GIPS offered covered only the code as distributed as part of the
>> RFC (although the language stating this was quite poorly constructed),
> Stop. All of you are confused.
> Maybe I can help—
> There are _two_  VP8 patent license grants:
> One for the specification:
> One for the software:
> These grants are subtly different in the scope of what they cover.
> There are important licensing drafting reasons for a construction
> which distinguishes "an implementation" and "any implementation".
> In particular, the license drafter writing this kind of a royalty free
> license has a tricky time making sure that the permission is broad
> enough to include all the correct coverage,  but not so over-broad that
> a malicious implementer could (e.g.) add a search engine to their VP8
> encoder and claim that the VP8 license entitles them to search patents.
> So, the drafter says something like— "those patent claims [...] that
> are necessarily infringed by implementation of this specification",
> which achieves the desired limited scope— and that is _all_ you get
> with the MPEG-LA pool patent licenses. This is what the Google bitstream
> spec license provides.
> But, if we're to be serious and honest about making a royalty free format
> and implementation that permission isn't quite sufficient: The reference
> implementation might practice some VP8 related techniques which are not
> "necessarily infringed"— they're helpful performance enhancements,
> they could simply be one option out of many ways of doing the same thing,
> or could just be something that was incidentally included (or even a
> malicious patent trap snake in the grass)— and so it's important that
> everything in the reference software also be licensed— even if its not
> "necessarily infringed" by the specification.   But since it's not a
> goal to also license unrelated things that a downstream user may cram in
> (e.g. a search engine), that license must be limited in scope to things
> which are actually in the reference implementation: "This grant does not
> include claims that would be infringed only as a consequence of further
> modification of this implementation." (this language is actually almost
> identical to the language for this purpose in the GPL, FWIW)
> So, in summary:
> You are licensed, via the bitstream license, for anything Google controls
> which is necessary to implement the specification— in hardware,
> software, home grown, or reference implementations.  This is pretty
> much as strong a grant as you can find anyone offering for any other
> format specification.
> You are also licensed, via the additional rights license, for any
> use of the VP8 reference implementation including modified versions,
> limited to the extent that the modifications don't expand the scope of
> the coverage. (Exactly as the GPL explicit patent grant does)
> This has already been clarified by Google on this list:
> "Google confirms that the VP8 patent grant applies to both
> third-party hardware and software implementations of VP8."
> I admit that the fact that there are two similar but distinct licenses
> is a little confusing, but I don't understand why we have to go over
> it again and again on this list.  I would think that the prior Google
> comment would have been sufficiently definitive.

Well, I apologize, somehow I missed that while catching up on this list. 
Your explanation certainly covers my concerns; the patent grant allows 
us to distribute modified versions, as long as they don't infringe on 
any patents that aren't necessarily infringed by the reference 
implementation. Thanks for the clue-bat :-)

Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
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