Re: [codec] Comments on draft-ietf-codec-ambisonics-01
Jan Skoglund <jks@google.com> Mon, 13 March 2017 22:17 UTC
Return-Path: <jks@google.com>
X-Original-To: codec@ietfa.amsl.com
Delivered-To: codec@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id A6A80129415 for <codec@ietfa.amsl.com>; Mon, 13 Mar 2017 15:17:47 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2
X-Spam-Level:
X-Spam-Status: No, score=-2 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_MESSAGE=0.001, RP_MATCHES_RCVD=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=google.com
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 GtoexPt64cMq for <codec@ietfa.amsl.com>; Mon, 13 Mar 2017 15:17:45 -0700 (PDT)
Received: from mail-qk0-x229.google.com (mail-qk0-x229.google.com [IPv6:2607:f8b0:400d:c09::229]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 8194B129BBF for <codec@ietf.org>; Mon, 13 Mar 2017 15:17:30 -0700 (PDT)
Received: by mail-qk0-x229.google.com with SMTP id p64so234842953qke.1 for <codec@ietf.org>; Mon, 13 Mar 2017 15:17:30 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=ETxtTz9xGxd+albsOg25/xbZ9sjq8jspy2MnSxLt3Cw=; b=H7AMQ1hYJolacgTeswL2scgi5jnIpF2MdjVSpYsSLxLZ3LP+VlOHQkA2cI2Z9WGilQ y3iTy0vU5L5LUm0bs6oGv51UVQa5BiNZHq07ehJhQkLSC2ihGflmWioQvDIX1wXDoFlF ldw4Bbg8z6oU2cNi89PxL4yc3zVaf3wkotLfeytstAOkOvSN9eLsVkjTyNLruldqWe8d S81mo+pt9SD77kGIm0yjUSukmyLHHSNqg7k/q9oZpc2QKt29GRYwEJ5byYm2A1o8mTEU cYsVzyQ6lF0KWnlJIYdOMjy6k89B6nKXEepEXH3b4cDy8ekH3aCOtH5sSRfvlyKFzvXA kdyQ==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to; bh=ETxtTz9xGxd+albsOg25/xbZ9sjq8jspy2MnSxLt3Cw=; b=s4e14u+8n9aepnvzDXy2OcRFy5IQ+MbbEy1ktQkkfYPm9XrskXt/V24Qy1rILJqA/C JSoVQE1g88pLer5rmJLr9+Qt/HUTHRpe75ziwjIf0q0OVRECG8lfICRfrBOIor9kNC4r OA8SNkSRzLc9OIFY/VJgI42UwK8jouCk+VppjZTpqqV3yUUBiIQEOuRKqohQKTEPcGPg HCi1SbpDpcA660829JQuTQMFe+qqnJpWnf1xegsBICO9G6CuFS0FT3bkiC4PUY6iJXO/ WhGMifjFMsZk2sLaYDAi7TyuiXw+mf3QanUgF4fzYiHJozuiB6PV+I4hPFHqEqSGxmi6 w1hA==
X-Gm-Message-State: AMke39n18wpBlJv1vBRMjaPKTqprtAtf+jVqJcBIhqmm3K+8yT4qSIUpX9H/THW3VvZD/XMfEQ0RT3l61E11r0Vl
X-Received: by 10.55.80.135 with SMTP id e129mr32210849qkb.192.1489443449424; Mon, 13 Mar 2017 15:17:29 -0700 (PDT)
MIME-Version: 1.0
References: <2f534e1b-b1af-266a-50ef-36f1739d878b@jmvalin.ca> <CAMdZqKGzdndiwpdXsYcHS7+r8Ega5LcQmAvcjiuHTHJgtTUwDg@mail.gmail.com> <CA+KMCSXhS2m4Dkous=4RkOibYWuoi+V_zBrhi1+anm-c+syQ1Q@mail.gmail.com> <CAMdZqKFDtD684HMkoO9bXi-c+g+8R+ay9kPdWSQOtHFDbC3ZLA@mail.gmail.com> <CABQ9DcuD+Et6+rBG-rCnWX-Dk-9STZMeYs-6fQWTk1kyjigRhw@mail.gmail.com> <52f5a570-e9f4-ea49-515e-498f0ed4f1bb@mozilla.com> <CABQ9Dcu0JVuAFvThSOgiBzxa+QOD4-1zpLzX6i-RKG7SRJnkNg@mail.gmail.com> <CABQ9Dct0d4id7wnzyu4sQHU=HZFVjCOXHCTO_F5RHcfE7HdH1Q@mail.gmail.com> <17622007-e5ce-0a08-67df-98c30a51e5a8@mozilla.com>
In-Reply-To: <17622007-e5ce-0a08-67df-98c30a51e5a8@mozilla.com>
From: Jan Skoglund <jks@google.com>
Date: Mon, 13 Mar 2017 22:17:18 +0000
Message-ID: <CA+KMCSVPHoav7QzdnvV5_TB2wFidkML0Z2+kp4VpJCU16N1+5Q@mail.gmail.com>
To: Jean-Marc Valin <jmvalin@mozilla.com>, Drew Allen <bitllama@google.com>, Mark Harris <mark.hsj@gmail.com>, "codec@ietf.org" <codec@ietf.org>
Content-Type: multipart/alternative; boundary="001a114a6b4eb7b9b2054aa4135b"
Archived-At: <https://mailarchive.ietf.org/arch/msg/codec/_Adbpb6YGOxdzXqvs_1S0co1cSc>
Subject: Re: [codec] Comments on draft-ietf-codec-ambisonics-01
X-BeenThere: codec@ietf.org
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: Codec WG <codec.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/codec>, <mailto:codec-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/codec/>
List-Post: <mailto:codec@ietf.org>
List-Help: <mailto:codec-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/codec>, <mailto:codec-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 13 Mar 2017 22:17:47 -0000
Hey, Our idea was to avoid a mapping table, potentially sparse, completely for family 2, and replacing it with a channel numbering list for family 3. Cheers, Jan On Mon, Mar 13, 2017 at 3:12 PM Jean-Marc Valin <jmvalin@mozilla.com> wrote: > On 13/03/17 06:04 PM, Drew Allen wrote: > > so just to be clear, if a user, say, wants to encode some mixed order > > ambisonics using ch253, how does the decoder know what ambisonic > > channels it has received and know how to render them correctly? > > Well, each line of the matrix would correspond to a channel in the > ambisonics channel order. If that channel isn't encoded, then the line > would have only zeros. > > The only way to avoid that situations would be to encode a separate D > value (D <= C) for the number of non-zero channels among the C > ambisonics channels possible. Then you'd store C values in the channel > mapping array (equivalent to a CxD permutation matrix), followed by a > Dx(M+N) weight matrix that would no longer have entire lines of zeros. > The result would be more compact in the case of sparse representation, > but IMO it'd be pretty ugly and prone to implementation errors. And if > you force D==C and don't code the D (which is what I'm proposing), then > the channel mapping permutation automatically becomes redundant. > > Cheers, > > Jean-Marc > > > On Mon, Mar 13, 2017 at 3:00 PM Drew Allen <bitllama@google.com > > <mailto:bitllama@google.com>> wrote: > > > > Got it. In that case, it certainly seems reasonable if I understand > > correctly. Thanks for clearing that up! > > > > On Mon, Mar 13, 2017 at 2:55 PM Jean-Marc Valin <jmvalin@mozilla.com > > <mailto:jmvalin@mozilla.com>> wrote: > > > > On 13/03/17 05:44 PM, Drew Allen wrote: > > > I think the issue is that the number of total channels rises > > > quadratically in respect to the ambisonic order (N + 1)^2. If > > a user > > > wants to use just the horizontal channels, it is only 2 * N + > > 1. If they > > > wish to code very high-order (>10th order) horizontal > > channels, they > > > would be artifically limited by all the zero channels being > > produced, > > > no? Or can this handled without actually creating all those > > empty channels? > > > > As far as I understand, the current draft already has all the > > limitations you're describing. The channel mapping array is > > basically > > equivalent to a CxC permutation matrix that multiplies the > Cx(N+M) > > weight matrix. The result is still a Cx(N+M) matrix, so using the > > resulting matrix as weights can still do everything without the > > need for > > the channel mapping to do the permutations. > > > > Cheers, > > > > Jean-Marc > > > > > On Mon, Mar 13, 2017 at 2:41 PM Mark Harris > > <mark.hsj@gmail.com <mailto:mark.hsj@gmail.com> > > > <mailto:mark.hsj@gmail.com <mailto:mark.hsj@gmail.com>>> > wrote: > > > > > > On Mon, Mar 13, 2017 at 10:38 AM, Jan Skoglund > > <jks@google.com <mailto:jks@google.com> > > > <mailto:jks@google.com <mailto:jks@google.com>>> wrote: > > > > Hey, > > > > > > > > Thanks for your comments > > > > > > > > On Mon, Mar 13, 2017 at 10:08 AM Mark Harris > > <mark.hsj@gmail.com <mailto:mark.hsj@gmail.com> > > > <mailto:mark.hsj@gmail.com <mailto:mark.hsj@gmail.com>>> > > wrote: > > > >> > > > >> On Fri, Feb 17, 2017 at 1:57 PM, Jean-Marc Valin > > > <jmvalin@jmvalin.ca <mailto:jmvalin@jmvalin.ca> > > <mailto:jmvalin@jmvalin.ca <mailto:jmvalin@jmvalin.ca>>> > > > >> wrote: > > > >> > 3.2. Channel Mapping Family 3 > > > >> > > > > >> > I would suggest removing the "Output Channel > > Numbering" field > > > because it > > > >> > is fully equivalent to simply permuting lines of the > > matrix. > > > Also, I > > > >> > believe that the size of the matrix was meant to be > > "32*(N+M)*C > > > bits" > > > >> > rather than "32*N*C bits". > > > >> > > > >> To expand on this a bit, a mapping family maps M+N > > decoded channels > > > >> (corresponding to the actual order of the coupled and > > uncoupled > > > >> channels in the bitstream) to C output channels > > (channels with a > > > >> specific semantic meaning). The additional "Output > Channel > > > Numbering" > > > >> table confuses things by adding an additional mapping > > from the output > > > >> channel numbers to a different set of numbers with > > actual semantic > > > >> meaning, leaving the output channel numbers with no > > apparent meaning. > > > >> > > > >> This does have a potential benefit as a matrix > > compression technique, > > > >> to reduce the size of the matrix when it would contain > > rows that are > > > >> all zero. However considering that the matrix occurs > > only once, and > > > >> mapping family 2 already offers a way to compress the > > matrix, this > > > >> alone does not seem worth the complexity of another > > level of > > > >> indirection. If matrix compression is desired it would > > probably be > > > >> less confusing to describe it in those terms and keep > > the semantic > > > >> meaning tied to the output channels. > > > >> > > > >> > > > >> The description of the Output Channel Numbering also > > does not specify > > > >> the intended behavior if the same value appears in the > > table multiple > > > >> times. > > > >> > > > >> Additionally, section 4.2 describes how to perform a > stereo > > > downmix of > > > >> mapping family 3, but makes assumptions about the > > output channel > > > >> numbering. This seems harmful and likely to promote > > implementations > > > >> that make similar assumptions. If it is necessary to > > apply the > > > output > > > >> channel numbering described in section 3.2 in order to > > implement a > > > >> correct stereo downmix, then it would be better to > > simply use the > > > >> output channels from section 3 as input to the downmix, > > consolidating > > > >> sections 4.1 and 4.2, rather than specify new formulas > > that make > > > >> assumptions about the mapping. That would also greatly > > simplify > > > >> section 4. > > > >> > > > >> Eliminating the Output Channel Numbering table as > > Jean-Marc suggests > > > >> should resolve these concerns. > > > > > > > > > > > > The problem is that once we allow mixed orders there is > > no unique > > > way for a > > > > receiver/decoder > > > > to resolve the mapping to ACNs from just a number of > > total output > > > channels. > > > > > > > > > In mapping family 2, the channel count (C) is the number > > of channels > > > in the fully periphonic configuration, but it is not > > necessary to > > > encode them all. The channel mapping table can map each > > ACN to a > > > specific decoded channel or to silence. For mixed order, > > some of the > > > ACNs will be mapped to silence and will not be encoded. > > > > > > In mapping family 3, the matrix can do everything that the > > channel > > > mapping table can do and more. Why not treat C in the > > same manner, as > > > the number of channels in the fully periphonic > > configuration, even if > > > some are silent? > > > > > > - Mark > > > > > > _______________________________________________ > > > codec mailing list > > > codec@ietf.org <mailto:codec@ietf.org> > > <mailto:codec@ietf.org <mailto:codec@ietf.org>> > > > https://www.ietf.org/mailman/listinfo/codec > > > > > > > > > > > > _______________________________________________ > > > codec mailing list > > > codec@ietf.org <mailto:codec@ietf.org> > > > https://www.ietf.org/mailman/listinfo/codec > > > > > > >
- [codec] Comments on draft-ietf-codec-ambisonics-01 Jean-Marc Valin
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Jean-Marc Valin
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Mark Harris
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Jan Skoglund
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Jan Skoglund
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Mark Harris
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Drew Allen
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Jean-Marc Valin
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Drew Allen
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Drew Allen
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Jean-Marc Valin
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Jan Skoglund
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Jean-Marc Valin
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Jan Skoglund
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Jean-Marc Valin
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Timothy B. Terriberry
- Re: [codec] Comments on draft-ietf-codec-ambisoni… Jan Skoglund