Re: [codec] I-D Action: draft-ietf-codec-oggopus-00.txt

Hi,

I have reviewed draft-ietf-codec-oggopus-00, and I have some questions and
comments. The Ogg format is new to me, so some of my comments might not
require any changes to the specification.

Section 3:
- In RFC 3533 "packet" is defined to be "created by the encoder of the
logical bitstream and represent meaningful entities for the encoder only",
but in this section it is said that "the first packet in the logical Ogg
bitstream MUST contain the identification (ID) header...". This header is
not part of the regular Opus bitstream, and is defined for the Ogg Opus
format only. does "packet" have a different meaning in this specification?
Or should it say "the first page.."?

Section 5:
- Would be great if you could mention the name of the two header packets in
the first section.

Section 5.1, list number 4:
- What is a cropped Ogg Opus stream?

Section 5.1, list number 5 (page 13):
- What does this mean "The original sample rate of the encoder input is not
preserved by the lossy compression"? You don't get perfect reconstruction,
of course, but you'll get the same audio bandwidth except for the 48 kHz
mode, or is there any other filtering affecting the bandwidth?

Section 5.1, list number 5 (page 13):
- There is a new numbered list within list number 5, which makes
the document hard to read.
- List number 3: Can be more clear: "...decode at the highest supported
rate above the hardware's sample rate and resample."
- Right after the list of 4 ways of choosing decode rate there is a fifth,
that is not in the list. I think it should be merged into the list as one
option.

Section 5.1.1, page 17:
- Family 1: Would be better if the Vorbis channel order was described in
this spec as well.

Section 5.2, list number 3:
- NUL -> NULL? or "null" as in section 5.1 list number 2, page 12.

/Tina

On Tue, Nov 20, 2012 at 12:00 AM, Timothy B. Terriberry
<tterribe@xiph.org>wrote:

> internet-drafts@ietf.org wrote:
>
>> A New Internet-Draft is available from the on-line Internet-Drafts
>> directories.
>>   This draft is a work item of the Internet Wideband Audio Codec Working
>> Group of the IETF.
>>
>
> The (other) chairs declared there was consensus to adopt this draft as a
> WG item and asked me to upload a new version of it.
>
> I have made a few minor edits from draft-terriberry-oggopus-01:
> 1) Fixed up the references.
> 2) Fixed a couple of typos.
> 3) Replaced a "should" with a "SHOULD" in Section 4.1.
> 4) Clarified the language around the starting granule position in the case
> that a) there is more audio in packets that complete on the first audio
> data page with a completed packet than the granule position indicates and
> b) the EOS flag is set on the same page (in this case you should not count
> forwards from 0, but should work backwards to figure out the real starting
> granule position).
> 5) Updated the acknowledgments.
>
> I have not incorporated any of the proposals that have been made to the
> list since the initial draft was posted (e.g., seamless chaining,
> replaygain tags, etc.).
>
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