Subject: [codec] I-D Action: draft-ietf-codec-oggopus-03.txt

From: [email-masked]
Date: Fri, 07 Feb 2014 15:57:51 -0800

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.

        Title           : Ogg Encapsulation for the Opus Audio Codec
        Authors         : Timothy B. Terriberry
                          Ron Lee
                          Ralph Giles
	Filename        : draft-ietf-codec-oggopus-03.txt
	Pages           : 29
	Date            : 2014-02-07

Abstract:
   This document defines the Ogg encapsulation for the Opus interactive
   speech and audio codec.  This allows data encoded in the Opus format
   to be stored in an Ogg logical bitstream.  Ogg encapsulation provides
   Opus with a long-term storage format supporting all of the essential
   features, including metadata, fast and accurate seeking, corruption
   detection, recapture after errors, low overhead, and the ability to
   multiplex Opus with other codecs (including video) with minimal
   buffering.  It also provides a live streamable format, capable of
   delivery over a reliable stream-oriented transport, without requiring
   all the data, or even the total length of the data, up-front, in a
   form that is identical to the on-disk storage format.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-codec-oggopus/

There's also a htmlized version available at:
http://tools.ietf.org/html/draft-ietf-codec-oggopus-03

A diff from the previous version is available at:
http://www.ietf.org/rfcdiff?url2=draft-ietf-codec-oggopus-03

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

---

From: Ralph Giles <[email-masked]>
Date: Fri, 07 Feb 2014 16:21:05 -0800

> 	Filename        : draft-ietf-codec-oggopus-03.txt

I've posted a new version of the Ogg Encapsulation draft for Opus.

The -03 draft just fixes some formatting issues in the -02 draft.

The -02 draft includes a couple of new sections over the -01 draft:

- Jean-Marc's encoder guidelines for lapping
- Tim's section on gap repair for RTP stream recording
- My recommended surround->stereo downmix matrices
- Text improved and clarified (we hope!)
- More and updated references

Thanks to everyone who sent feedback on the earlier drafts.

I'm happier with this one. As far as the authors are concerned, there
are two issues left outstanding by this version:

(1) We'd like to give more specific instructions for setting pre-skip
values 'in such a way' as to properly cross-lap when performing
compressed stream editing. Section 7.2, step 4.

(2) We haven't addressed Calvin Walton's questions about the various
gain headers.

The idnits program complains about our normative references to RFC 3533
"Ogg Encapsulation Format", which is Informational. I think this should
be acceptable since it documents an already established format. I
haven't preceived any need for a 3533bis, so doing the work to produce a
Standards Track revision makes little sense.

It likewise complains about our citation of EBU-128, which I believe is
similarly acceptable. It is the industry standard reference for the
applicable technique.

Comments on the new draft welcome!

Cheers,
 -r

---

From: Calvin Walton <[email-masked]>
Date: Fri, 28 Feb 2014 09:48:22 -0500

> (2) We haven't addressed Calvin Walton's questions about the various

I just want to try to restate and clarify my opinion on this a bit:

The ReplayGain tags are application-specific metadata tags defined by a
specification that is managed externally to the IETF[1].

As such, I don't think it's appropriate for the Ogg Opus specification
to state whether or not the REPLAYGAIN tags should be present in the
file, or their specific semantics. Any required changes for handling
ReplayGain in Ogg Opus should probably be done in the ReplayGain specs
themselves.

-

One question I'm not sure about. Is the proposed R128_TRACK_GAIN field
supposed to be a generic vorbis comment standard that can be used in
multiple formats? (e.g. Ogg Vorbis, Flac), or is it intended only for
use in Opus?

If the former, it should probably be proposed in a more general way.
Inasmuch as there is no real standardization organization for
multi-format vorbis comment fields, a discussion on the HydrogenAudio
forums may be a good place to see if there is any interest in adopting
the comment format.

Having a uniform set of tag names for vorbis comments is advantageous to
people building music players and decoding libraries, since it means
that vorbis comment parsing code can be shared between multiple formats.

1) It's currently published on the HydrogenAudio wiki.
Current standard (David Robinson's original calculation algorithm)
http://wiki.hydrogenaudio.org/index.php?title=ReplayGain_1.0_specification
Proposed revision (updated algorithm based on EBU-R128 with gain offset)
http://wiki.hydrogenaudio.org/index.php?title=ReplayGain_2.0_specification

-- 
Calvin Walton <[email-masked]>