Re: [rtcweb] Resolution negotiation - mandatory / advisory resolutions

"Roni Even" <ron.even.tlv@gmail.com> Thu, 19 April 2012 08:20 UTC

Return-Path: <ron.even.tlv@gmail.com>
X-Original-To: rtcweb@ietfa.amsl.com
Delivered-To: rtcweb@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 8242C21F858F for <rtcweb@ietfa.amsl.com>; Thu, 19 Apr 2012 01:20:16 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -3.479
X-Spam-Level:
X-Spam-Status: No, score=-3.479 tagged_above=-999 required=5 tests=[AWL=0.120, BAYES_00=-2.599, RCVD_IN_DNSWL_LOW=-1]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id o2Xj8al6kpkt for <rtcweb@ietfa.amsl.com>; Thu, 19 Apr 2012 01:20:11 -0700 (PDT)
Received: from mail-we0-f172.google.com (mail-we0-f172.google.com [74.125.82.172]) by ietfa.amsl.com (Postfix) with ESMTP id 35B1921F8565 for <rtcweb@ietf.org>; Thu, 19 Apr 2012 01:20:10 -0700 (PDT)
Received: by werb10 with SMTP id b10so6422886wer.31 for <rtcweb@ietf.org>; Thu, 19 Apr 2012 01:20:09 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:references:in-reply-to:subject:date:message-id:mime-version :content-type:content-transfer-encoding:x-mailer:thread-index :content-language; bh=U1H66F4lr2q+ShTNdT4rkR7gQabV1dk8A8Xs4GSqEho=; b=GRH1HTnX6kHtqIkQ6YetyZxNWsm4HDynC4gUBObdaxzcIxUUY9KfbYL5bJNdYxxQ2y XMiUpfLq6RsefXKGT5bpxvr+7O9X5EkoKcGUkAQO4JBWhQU4ZMQdMIo0Va/D+V1ruzaL 2jc4/wIY3NdCkOto8vl/nYMdxPXe2zeAkbssXCfee/zStO4uwvvQ67GnxwXJM68emzuY M3XLiGVPJ1VDdxd1cqMpf6FFIelfkZvPAbCtfgGYIV0rZV5HcnkBPWeTWqzkIc/yjj7D Y6y4PCLT8xT4luOlKmOJTgWzj5/I1nrSDhcecou3eFxLxwtB1zZRjfcXtNy/TM5JK9XJ 7x/A==
Received: by 10.216.205.93 with SMTP id i71mr731530weo.51.1334823609328; Thu, 19 Apr 2012 01:20:09 -0700 (PDT)
Received: from windows8d787f9 ([109.65.204.117]) by mx.google.com with ESMTPS id gg2sm5853462wib.7.2012.04.19.01.20.07 (version=TLSv1/SSLv3 cipher=OTHER); Thu, 19 Apr 2012 01:20:08 -0700 (PDT)
From: "Roni Even" <ron.even.tlv@gmail.com>
To: "'Harald Alvestrand'" <harald@alvestrand.no>, <rtcweb@ietf.org>
References: <4F869648.2020605@alvestrand.no> <4F8FC2E0.60701@alvestrand.no>
In-Reply-To: <4F8FC2E0.60701@alvestrand.no>
Date: Thu, 19 Apr 2012 11:18:33 +0300
Message-ID: <4f8fcab8.c268b40a.7fe1.ffffb433@mx.google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
X-Mailer: Microsoft Office Outlook 12.0
Thread-Index: Ac0eAJOsIQudWrn3Qru2QYVYap6e+wAA+jWQ
Content-Language: en-us
Subject: Re: [rtcweb] Resolution negotiation - mandatory / advisory resolutions
X-BeenThere: rtcweb@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Real-Time Communication in WEB-browsers working group list <rtcweb.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/rtcweb>
List-Post: <mailto:rtcweb@ietf.org>
List-Help: <mailto:rtcweb-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 19 Apr 2012 08:20:17 -0000

Hi Harald,
The reason for the language was that this is really what the receiver wished
to receive. The issue is that at least for H.264 there is no mandatory
requirement for the encoder to support all resolutions within the supported
level. The receiver must be able to crop and scale.
 
Roni Even

> -----Original Message-----
> From: rtcweb-bounces@ietf.org [mailto:rtcweb-bounces@ietf.org] On
> Behalf Of Harald Alvestrand
> Sent: Thursday, April 19, 2012 10:47 AM
> To: rtcweb@ietf.org
> Subject: Re: [rtcweb] Resolution negotiation - mandatory / advisory
> resolutions
> 
> When discussing the issue of resolution negotiation locally, we found a
> quandary:
> 
> We have two different negotiation needs:
> - Maximum resolution that's possible to use in a given context
> - The preferred resolution for a given context
> 
> The current imageattr= spec (RFC 6236) doesn't specify clearly whether
> the result of the negotiation is to be considered mandatory or advisory
> (it uses the term "wishes" a lot), but the description reads most
> consistently if one assumes that it is a "MUST" type request.
> 
> One interpretation is that the highest functionality available in the
> spec is the "limit", while the highest q value is the "preference",
> thus:
> 
> recv [x=320,y=200,q=1.0] [x=200:1024,y=160:768,q=0.1]
> 
> would indicate that the receiver is capable of 200x160 to 1024x768, but
> wants 320x200.
> 
> This maps reasonably to the capabilities spec's talk about "mandatory"
> vs "optional" capabilities.
> 
> Does this interpretation make sense?
> 
>                        Harald
> 
> 
> On 04/12/2012 10:46 AM, Harald Alvestrand wrote:
> > Hello folks,
> >
> > after the IETF, I've attempted to gather together information about
> > resolution negotiation and what we might need to do there.
> >
> > I pulled together the paragraphs below - this may want to be
> > incorporated in an I-D on "SDP usage in RTCWEB", or it may want to go
> > somewhere else. Chairs' guidance is appreciated.
> >
> > At the moment, I have it in xml2rfc format, so it should be easy to
> do
> > cut-and-paste on it, but don't want to push it as a separate I-D
> > unless that's what the chairs desire.
> > Note - there are some QUERY sections in there - I'm unsure what those
> > should be resolved to.
> >
> > Comments?
> >
> >                          Harald
> >
> > 2.  Requirements
> >
> >    The relevant requirement for video resolution negotiation from the
> >    RTCWEB use cases document
> >    [I-D.ietf-rtcweb-use-cases-and-requirements] is:
> >
> >    o  F25 The browser SHOULD use encoding of streams suitable for the
> >       current rendering (e.g. video display size) and SHOULD change
> >       parameters if the rendering changes during the session.
> >
> >    The resulting need is:
> >
> >    o  To negotiate a maximum spatial resolution for all videos at
> call
> >       setup time
> >
> >    o  To negotiate a maximum temporal resolution ("frame rate")
> across
> >       all videos at call setup time
> >
> >    o  To indicate the desire of the recipient for a particular
> spatial
> >       or temporal resolution on a particular video source
> >
> >    o  To indicate the intent of the sender to send a video source in
> a
> >       particular spatial or temporal resolution
> >
> >    This document does not mention other requirements.
> 
> _______________________________________________
> rtcweb mailing list
> rtcweb@ietf.org
> https://www.ietf.org/mailman/listinfo/rtcweb