Re: [rtcweb] Asymmetric codecs
Justin Uberti <juberti@google.com> Mon, 25 November 2013 20:21 UTC
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References: <CEB676E0.1ED44%mzanaty@cisco.com> <7594FB04B1934943A5C02806D1A2204B1C55441B@ESESSMB209.ericsson.se> <5292FD9D.3020207@bbs.darktech.org> <7594FB04B1934943A5C02806D1A2204B1C554536@ESESSMB209.ericsson.se> <52938846.3040803@bbs.darktech.org>
From: Justin Uberti <juberti@google.com>
Date: Mon, 25 Nov 2013 12:21:15 -0800
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To: cowwoc <cowwoc@bbs.darktech.org>
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Subject: Re: [rtcweb] Asymmetric codecs
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SDP is just a serialization format, a clumsy yet somehow popular one. Nothing we decide here on codecs will impose any mandate on what serialization format is used in WebRTC 2.0. On Mon, Nov 25, 2013 at 9:26 AM, cowwoc <cowwoc@bbs.darktech.org> wrote: > > <cough> told you so <cough> :) > > So folks, what happens when we try removing any mention of SDP from the > 2.0 spec? :) Are you saying this is no longer possible? > > Gili > > > On 25/11/2013 2:43 AM, Christer Holmberg wrote: > > Hi, > > > > I’m afraid that SDP has become is a little more than an implementation > detail :) > > > > Regards, > > > > Christer > > > > *From:* rtcweb [mailto:rtcweb-bounces@ietf.org <rtcweb-bounces@ietf.org>] *On > Behalf Of *cowwoc > *Sent:* 25. marraskuuta 2013 9:35 > *To:* rtcweb@ietf.org > *Subject:* Re: [rtcweb] Asymmetric codecs > > > > > SDP is supposed to be an implementation detail. Let's figure out whether > asymmetric codecs solve our problems and wedge it into SDP later. > > I suspect that this approach reduces the IPR risk, but H.264 royalties > still apply, do they not? > > Sadly this means we're stuck with: "MUST decode at least two of [VP8, > H.264, H.261] and MUST encode at least one of them". > > Gili > > On 25/11/2013 2:24 AM, Christer Holmberg wrote: > > Hi, > > > > First, from a pure MTI codec perspective, the question is whether usage of > asymmetric codecs would solve the issues that people have. > > > > Second, from an SDP OA/BUNDLE perspective, I don’t think we can mandate > *usage* of BUNDLE. And, even if we did, in the initial Offer you still > need to assign unique port values for each m- line (as agreed in Vancouver). > > > > …unless, of course, you assign an SDP ‘bundle-only’ attribute to all m- > lines with asymmetric codecs. > > > > Regards, > > > > Christer > > > > *From:* Mo Zanaty (mzanaty) [mailto:mzanaty@cisco.com <mzanaty@cisco.com>] > > *Sent:* 25. marraskuuta 2013 4:11 > *To:* Christer Holmberg; Martin Thomson; Paul Giralt (pgiralt) > *Cc:* rtcweb@ietf.org > *Subject:* Asymmetric codecs > > > > I started a draft on how to standardize support for asymmetric codecs back > in September. The primary motivation was decoding H.264 and H.265 while > only encoding H.264. A secondary motivation, for rtcweb, was decoding H.264 > and VP8 while only encoding one of them, as Stefan mentioned. I thought it > would be a trivial thing to write up by the Oct. 6 deadline for MTI > proposals. The draft is still incomplete and unpublished because all > solutions are ugly and overly complex for something so seemingly trivial, > just like bundle and unified plan. I now sympathize with Christer and Adam > for how they arrived at those (not exactly elegant) solutions, and agree > with Martin that a pair of (bundled) m-lines is the most viable (although > not exactly elegant) solution for asymmetric codecs. > > > > RFC 4317 drafts originally included asymmetric codecs until they were > removed in draft 02: > > > http://tools.ietf.org/rfcdiff?difftype=--hwdiff&url2=draft-ietf-mmusic-offer-answer-examples-02.txt > > > > They were removed for fear of issues with shared ports: > > http://www.ietf.org/mail-archive/text/mmusic/2003-09.mail > > > > Now that we (almost) have bundle, can we resurrect asymmetric codecs with > separate sendonly and recvonly m-lines? Are folks ok with a dependency on > bundle? I would be happy to complete a draft in that direction. (That is, a > general mmusic draft on asymmetric codecs, not a rtcweb draft on MTI > asymmetric codecs. I will move the discussion to mmusic after getting > rtcweb opinions first.) > > > > Some may consider this a bizarre corner case. However, for hardware > codecs, it is the norm not the exception to have asymmetric encoder and > decoder formats. Especially for new formats, which usually appear in > hardware decoders well before hardware encoders are available. This > happened for H.264, H.265, VP8, and virtually every popular codec format in > virtually every popular chipset. > > > > Mo > > > > On 11/23/13, 9:09 AM, Christer Holmberg <christer.holmberg@ericsson.com> > wrote: > > Like some others, I think the must-decode-both-must-endcode-one > alternative as such sounds interesting (whether it has any impact on the > licence/IPR issues I'll leave to others to speak for). However, I have big > concerns over the proposal to indicate sendrecv for a codec even if an > entity is only able to receive/decode it. … Usage of unidirectional, > sendonly/recvonly, m- line would of course solve this, and you might know > that it is one option we are discussing in CLUE (for other reasons than MTI > codec, though). > > > > On 22 November 2013 16:20, Paul Giralt (pgiralt) <pgiralt@cisco.com> > wrote: > > I gave this as an example of a possible way to do it, but that means you > need two separate m= lines - one for send and one for receive. Seems > strange to do this for something that you really want to be a single > bi-directional stream. > > > > On 11/22/13, 8:03 PM, Martin Thomson <martin.thomson@gmail.com> wrote: > > The bidirectional thing in O/A is the strange way to do things. Two lines > is pretty intuitive. > > > > > > > _______________________________________________ > > rtcweb mailing list > > rtcweb@ietf.org > > https://www.ietf.org/mailman/listinfo/rtcweb > > > > > > _______________________________________________ > rtcweb mailing list > rtcweb@ietf.org > https://www.ietf.org/mailman/listinfo/rtcweb > >
- [rtcweb] Asymmetric codecs Mo Zanaty (mzanaty)
- Re: [rtcweb] Asymmetric codecs Christer Holmberg
- Re: [rtcweb] Asymmetric codecs cowwoc
- Re: [rtcweb] Asymmetric codecs Christer Holmberg
- Re: [rtcweb] Asymmetric codecs Stefan Håkansson LK
- Re: [rtcweb] Asymmetric codecs Mo Zanaty (mzanaty)
- Re: [rtcweb] Asymmetric codecs Mo Zanaty (mzanaty)
- Re: [rtcweb] Asymmetric codecs cowwoc
- Re: [rtcweb] Asymmetric codecs Basil Mohamed Gohar
- Re: [rtcweb] Asymmetric codecs Justin Uberti
- Re: [rtcweb] Asymmetric codecs cowwoc