Re: [rtcweb] Resolution negotiation - mandatory / advisory resolutions
Harald Alvestrand <harald@alvestrand.no> Thu, 19 April 2012 08:47 UTC
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Date: Thu, 19 Apr 2012 10:47:40 +0200
From: Harald Alvestrand <harald@alvestrand.no>
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To: Roni Even <ron.even.tlv@gmail.com>
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Cc: rtcweb@ietf.org
Subject: Re: [rtcweb] Resolution negotiation - mandatory / advisory resolutions
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On 04/19/2012 10:18 AM, Roni Even wrote: > Hi Harald, > The reason for the language was that this is really what the receiver wished > to receive. The strength of his wish may be the issue here.... > 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. I couldn't parse that. Does the sender have to (MUST) send a resolution within the boundaries of the "recv" spec, or can he send something outside it? (ie if the receiver sends recv [x=320,y=200], can the sender send something with x=320,y=240, or is he completely constrained?) What does the receiver have to be able to do? Harald > > 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 >
- [rtcweb] Resolution negotiation - a contribution Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - a contribut… Timothy B. Terriberry
- Re: [rtcweb] Resolution negotiation - a contribut… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - a contribut… Marshall Eubanks
- Re: [rtcweb] Resolution negotiation - a contribut… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - a contribut… Stephan Wenger
- Re: [rtcweb] Resolution negotiation - a contribut… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - a contribut… Stephan Wenger
- Re: [rtcweb] Resolution negotiation - a contribut… Harald Alvestrand
- [rtcweb] VP8 payload, decoder processing capabili… Stephan Wenger
- Re: [rtcweb] [payload] VP8 payload, decoder proce… Yuepeiyu (Roy)
- Re: [rtcweb] Resolution negotiation - mandatory /… Roni Even
- Re: [rtcweb] Resolution negotiation - mandatory /… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - mandatory /… Roni Even
- Re: [rtcweb] Resolution negotiation - mandatory /… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - mandatory /… Harald Alvestrand
- Re: [rtcweb] Resolution negotiation - mandatory /… Roni Even
- [rtcweb] Alternative Proposal for Dynamic Codec P… Magnus Westerlund
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Harald Alvestrand
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Timothy B. Terriberry
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Bernard Aboba
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Harald Alvestrand
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Justin Uberti
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Magnus Westerlund
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Harald Alvestrand
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Magnus Westerlund
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Justin Uberti
- Re: [rtcweb] Alternative Proposal for Dynamic Cod… Magnus Westerlund
- Re: [rtcweb] [payload] VP8 payload, decoder proce… Cullen Jennings (fluffy)
- Re: [rtcweb] [payload] VP8 payload, decoder proce… Harald Alvestrand