[opus] Channel Mapping Family for Ambisonics

Jean-Marc Valin jmvalin at jmvalin.ca
Fri May 27 00:41:50 UTC 2016

Hi Michael,

Here's some more minor comments below. As long as you address the two
comments from my previous email (254 -> 2 and the draft name), the draft
is good for submitting as initial version on the IETF website (even if
you don't address all the minor comments from this email). FYI, this is
the address for submitting a new draft:

Introduction: "The Ogg format is a container which transmission and
storage of audio coded using the Opus codec."

I think I forgot a word in this sentence. Also, Ogg is a general
container and isn't just for Opus.

Section 3: "A demuxer implmentation encountering Channel Mapping Family
254 SHOULD interpret the Opus stream as containing ambisonics with the
format described in Section 3.1."

Aside from changing 254 to 2, the "SHOULD" should be a "MUST".

Section 3.1: "Allowed numbers of channels: (1 + l)^2 for l = 0...14"

Minor nit: unless the use of "l" is standard for talking about
ambisonics, I would suggest using "k" instead, since "l" is easy to
confuse with "1".

Section 3.1: If it's not too complicated, can you explain how the "m"
index is derived?



On 05/26/2016 05:56 PM, Michael Graczyk wrote:
> Hello Tim and others,
> Thanks for your help explaining this process on IRC. I wrote out a
> first draft in the RFC xml format. I have attached the xml (labeled as
> xml.txt so it will appear inline) and the rendered txt files. Please
> let me know where I can make improvements. I will upload this draft to
> the IETF datatracker and send it out to codec@ after addressing your
> comments.
> _______________________________________________
> opus mailing list
> opus at xiph.org
> http://lists.xiph.org/mailman/listinfo/opus

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