Subject: [rtcweb] Video Open issue #4: VP8 filters

From: Adam Roach <[email-masked]>
Date: Thu, 12 Feb 2015 14:48:54 -0600

In Toronto, there was a claim that specification that "bilinear" and 
"none" filters is superfluous, as they are already required as part of 
the VP8 spec. Since that time, I have repeatedly asked for a concrete 
pointer to the text that would make this unnecessary.

No one has come forth with such a pointer. Given the harmless nature of 
redundantly specifying this requirement on implementations and the lack 
of concrete evidence for its removal, I am leaving the text as-is and 
removing the open issue from my list.

/a

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From: Harald Alvestrand <[email-masked]>
Date: Thu, 12 Feb 2015 22:00:45 +0100

On 02/12/2015 09:48 PM, Adam Roach wrote:
> No one has come forth with such a pointer. Given the harmless nature 
> of redundantly specifying this requirement on implementations and the 
> lack of concrete evidence for its removal, I am leaving the text as-is 
> and removing the open issue from my list.

Please. This is not harmless.

The text under consideration is

6.1.  VP8

    For the VP8 codec, defined in [RFC6386], endpoints MUST support the
    payload formats defined in [I-D.ietf-payload-vp8].  In addition they
    MUST support the 'bilinear' and 'none' reconstruction filters.

The problem with the text is not that it specifies that one MUST support 
the "bilinear" and "none" filters.

The problem with the text is that in order for it to make any sense at 
all, one must believe that you can be conformant with RFC 6386 without 
the ability to decode all the specified reconstruction filters - that 
is, in order for the second sentence to make any sense at all, one must 
believe that filters are optional.

There is no hint in any place in RFC 6386 that a conformant decoder can 
be conformant without the ability to decode bitstreams using all the 
filter types. Filters are not optional for the decoder.

This is the point I'm objecting to.

Harald

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From: Bjoern Hoehrmann <[email-masked]>
Date: Thu, 12 Feb 2015 22:05:55 +0100

* Adam Roach wrote:
>Given the harmless nature of redundantly specifying this requirement

I do not see how that could be harmless, whatever the requirement.
-- 
Björn Höhrmann · mailto:[email-masked] · http://bjoern.hoehrmann.de
D-10243 Berlin · PGP Pub. KeyID: 0xA4357E78 · http://www.bjoernsworld.de
 Available for hire in Berlin (early 2015)  · http://www.websitedev.de/

---

From: Mohammed Raad <[email-masked]>
Date: Thu, 12 Feb 2015 23:25:30 +0200

Hi,

Why not remove the second sentence? It clearly introduces an implied
interpretation to RFC 6386 that is incorrect.

Mohammed

On Thu, Feb 12, 2015 at 11:00 PM, Harald Alvestrand <[email-masked]>
wrote:

>> "none" filters is superfluous, as they are already required as part of the
>> VP8 spec. Since that time, I have repeatedly asked for a concrete pointer
>> to the text that would make this unnecessary.
>>
>> redundantly specifying this requirement on implementations and the lack of
>> concrete evidence for its removal, I am leaving the text as-is and removing
>> the open issue from my list.
>>
>
> all, one must believe that you can be conformant with RFC 6386 without the
> ability to decode all the specified reconstruction filters - that is, in
> order for the second sentence to make any sense at all, one must believe
> that filters are optional.
>
> There is no hint in any place in RFC 6386 that a conformant decoder can be
> conformant without the ability to decode bitstreams using all the filter
> types. Filters are not optional for the decoder.
>
> _______________________________________________
> rtcweb mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/rtcweb
>

-- 
Mohammed Raad, PhD.
Partner
RAADTECH CONSULTING
P.O. Box 113
Warrawong
NSW 2502 Australia
Phone: +61 414451478
Email: [email-masked]

---

From: Adam Roach <[email-masked]>
Date: Fri, 13 Feb 2015 11:10:02 -0600

Well, I guess fifth time asking is the charm.

Consensus seems to be to remove this sentence -- so it's gone.

/a

On 2/12/15 15:00, Harald Alvestrand wrote:
>> "none" filters is superfluous, as they are already required as part 
>> of the VP8 spec. Since that time, I have repeatedly asked for a 
>> concrete pointer to the text that would make this unnecessary.
>>
>> lack of concrete evidence for its removal, I am leaving the text 
>> as-is and removing the open issue from my list.
>
> The problem with the text is not that it specifies that one MUST 
> support the "bilinear" and "none" filters.
>
> is, in order for the second sentence to make any sense at all, one 
> must believe that filters are optional.
>
> There is no hint in any place in RFC 6386 that a conformant decoder 
> can be conformant without the ability to decode bitstreams using all 
> the filter types. Filters are not optional for the decoder.
>