Re: [codec] Benjamin Kaduk's No Objection on draft-ietf-codec-ambisonics-07: (with COMMENT)
Benjamin Kaduk <kaduk@mit.edu> Mon, 06 August 2018 17:54 UTC
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Date: Mon, 06 Aug 2018 12:54:43 -0500
From: Benjamin Kaduk <kaduk@mit.edu>
To: Jan Skoglund <jks@google.com>
Cc: The IESG <iesg@ietf.org>, draft-ietf-codec-ambisonics@ietf.org, Tim Terriberry <tterriberry@mozilla.com>, codec-chairs@ietf.org, codec@ietf.org
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Subject: Re: [codec] Benjamin Kaduk's No Objection on draft-ietf-codec-ambisonics-07: (with COMMENT)
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On Mon, Aug 06, 2018 at 07:43:30PM +0200, Jan Skoglund wrote: > Thanks for the comments! Our responses are inline below. A new version of > the draft has been uploaded. > > Cheers, > Jan > > > > I see that Section 5.2 attempts to Update RFC 7845 to allow for the larger > > channel mapping information used by family 3, but I'm still a little > > unclear about what behavior I should expect from a pure RFC 7845 > > implementation that receives a family 3 stream. The actual mapping table > > would be "too long", but would the implementation detect that, or just note > > that it's an unrecognized family and generate silence? > > > > This is the reason the changes below to 7845 are necessary. I.e., not > interpreting as channel mapping family 255, and instead “A > demuxer implementation encountering a 'channel mapping family' > value that it does not recognize SHOULD NOT attempt to decode the > packets“ > I think that, depending on implementation, an old decoder would interpret a > Q15 value as an index and either, most likely, decide the value to be > invalid and not decode, or, if the index is lower-valued, decode the > streams according to the old rule > “If 'index' is less than 2*M, the output MUST be taken from > decoding stream ('index'/2) as stereo and selecting the left > channel if 'index' is even, and the right channel if 'index' is > odd. If 'index' is 2*M or larger, but less than 255, the output > MUST be taken from decoding stream ('index' - M) as mono. If > 'index' is 255, the corresponding output channel MUST contain > pure silence” > So, it would either decode and play an unintended mixing, or not produce > audio at all. Did you consider adding some text describing this situation to the document? I guess it is not strictly required from a protocol description point of view, but would probably save readers some effort, when aggregated over time. > > > > > Section 1 > > > > I think we want to say "by adding itesm with values 2 and 3" to the > > registry, since we add two entries and not a single superposed entry. > > > > Changed. > > > > Section 3.1 > > > > While I can deduce this from the list of allowed numbers of channels, > > noting that both ends of the range (0 and 14) are allowed values probably > > would add clarity. > > > > It is now written as ”n = 0, 1, …, 14” , which we feel that most readers > will interpret such that all integers in the given range, including 0 and > 14, are valid. > > > > Section 3.2 > > > > Figure 3 could perhaps make it more clear that C and K are not necessarily > > equal. > > > > > We feel it's sufficiently clear in the figure, since the endpoints of the > vectors, and the rows and columns have specifically differently named > values (C and K). Added a mention in the paragraph. > > > > The term "side information" is used without definition (and is not used in > > RFC 7845). Does this clause really add anything in comparison to if we > > just say "The matrix MUST be provided in the channel mapping table portion > > of the identification header, in place of a normal channel mapping table"? > > > > > Changed. > > > > Section 5.1 > > > > Family 255 is specified in Section 5.1.1.3 of RFC 7845, not 5.1.1.4. > > (Also, the unqualified Section references should probably all be of the > > form Section N of RFC 7845, for the benefift of the HTML linkification > > tooling.) > > > > Changed. > > > > Section 8 > > > > Sometimes I see a "Description" column that allows for in-registry > > visibility that a range is for experimental usage. I suppose it would not > > be too hard to also modify the registry structure to add such a thing, if > > you want. > > > > > Perhaps, but I’m afraid I wouldn’t know how to do that:) We can help you out if you do want to go down that route, but I don't think anyone is insisting on it :) Thanks, Benjamin
- [codec] Benjamin Kaduk's No Objection on draft-ie… Benjamin Kaduk
- Re: [codec] Benjamin Kaduk's No Objection on draf… Jan Skoglund
- Re: [codec] Benjamin Kaduk's No Objection on draf… Benjamin Kaduk
- Re: [codec] Benjamin Kaduk's No Objection on draf… Ralph Giles