Re: [rtcweb] Asymmetric codecs

Christer Holmberg <christer.holmberg@ericsson.com> Mon, 25 November 2013 07:25 UTC

Return-Path: <christer.holmberg@ericsson.com>
X-Original-To: rtcweb@ietfa.amsl.com
Delivered-To: rtcweb@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 6A20D1AC7F2 for <rtcweb@ietfa.amsl.com>; Sun, 24 Nov 2013 23:25:16 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.95
X-Spam-Level:
X-Spam-Status: No, score=-1.95 tagged_above=-999 required=5 tests=[HELO_EQ_SE=0.35, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_MED=-2.3, SPF_PASS=-0.001] autolearn=ham
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 1JAqsvBTFGTE for <rtcweb@ietfa.amsl.com>; Sun, 24 Nov 2013 23:25:13 -0800 (PST)
Received: from mailgw7.ericsson.se (mailgw7.ericsson.se [193.180.251.48]) by ietfa.amsl.com (Postfix) with ESMTP id 2BF9F1AC43E for <rtcweb@ietf.org>; Sun, 24 Nov 2013 23:25:11 -0800 (PST)
X-AuditID: c1b4fb30-b7f228e000003e6c-75-5292fb4002aa
Received: from ESESSHC008.ericsson.se (Unknown_Domain [153.88.253.125]) by mailgw7.ericsson.se (Symantec Mail Security) with SMTP id E9.6A.15980.14BF2925; Mon, 25 Nov 2013 08:24:49 +0100 (CET)
Received: from ESESSMB209.ericsson.se ([169.254.9.73]) by ESESSHC008.ericsson.se ([153.88.183.42]) with mapi id 14.02.0328.009; Mon, 25 Nov 2013 08:24:01 +0100
From: Christer Holmberg <christer.holmberg@ericsson.com>
To: "Mo Zanaty (mzanaty)" <mzanaty@cisco.com>, Martin Thomson <martin.thomson@gmail.com>, "Paul Giralt (pgiralt)" <pgiralt@cisco.com>
Thread-Topic: Asymmetric codecs
Thread-Index: AQHO6YOHQHY8Un59WEC1K24yFUskgZo1iRZw
Date: Mon, 25 Nov 2013 07:24:00 +0000
Message-ID: <7594FB04B1934943A5C02806D1A2204B1C55441B@ESESSMB209.ericsson.se>
References: <CEB676E0.1ED44%mzanaty@cisco.com>
In-Reply-To: <CEB676E0.1ED44%mzanaty@cisco.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [153.88.183.18]
Content-Type: multipart/alternative; boundary="_000_7594FB04B1934943A5C02806D1A2204B1C55441BESESSMB209erics_"
MIME-Version: 1.0
X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrELMWRmVeSWpSXmKPExsUyM+Jvra7j70lBBlP3m1tcO/OP0eLFgzlM FjcbHjNarP3Xzu7A4jHl90ZWj52z7rJ7LFnykymAOYrLJiU1J7MstUjfLoErY3FjaMHx2opT N68yNjC25nUxcnJICJhItH3ZywJhi0lcuLeerYuRi0NI4BCjxJ0dp5ghnMWMEn/2XADKcHCw CVhIdP/TBomLCLQzSsw51sIO0s0soC5xZ/E5MFtYQE6i8fMiRhBbREBe4vaNO6wQtpHElw+n wLaxCKhKLJi6AGwmr4CvxLtFOiBhIQE9iQnTHzKB2JwC+hLLV6wFK2cEOu77qTVMEKvEJW49 mc8EcbSAxJI955khbFGJl4//sULYihIfX+1jhKjPl3i39AcbiM0rIChxcuYTlgmMorOQjJqF pGwWkjKIuI7Egt2f2CBsbYllC18zw9hnDjxmQhZfwMi+ipE9NzEzJ73cfBMjMN4ObvltsINx 032xQ4zSHCxK4rwf3joHCQmkJ5akZqemFqQWxReV5qQWH2Jk4uCUamCUuyRdfHlFcM7iM7f0 G5jlNllZhtxi5tX5pWZ5MzG98HJ2UrpUauDSQ0qade9ivt3Qyqn+ezjl7pqbTPPsW4xO7vba 5P9UL//U6QdmMSc4r19bVFz3Ml62YVb/wV0XG+v2TlvdUrTOdOPGS/9XryntYFywZdaXN1L2 D2pf3mfuLVwYJ17dvklIiaU4I9FQi7moOBEAYl8IyoUCAAA=
Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Asymmetric codecs
X-BeenThere: rtcweb@ietf.org
X-Mailman-Version: 2.1.15
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: Mon, 25 Nov 2013 07:25:16 -0000

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]
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<mailto: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<mailto: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<mailto:martin.thomson@gmail.com>> wrote:
The bidirectional thing in O/A is the strange way to do things.  Two lines is pretty intuitive.