Subject: Re: [codec] [Matroska-devel] Opus in Matroksa Cont.

From: "Timothy B. Terriberry" <[email-masked]>
Date: Fri, 05 Jul 2013 12:34:38 -0700

Cross-posting to codec: N.B. that 
<http://www.ietf.org/about/note-well.html> applies to replies there.

Moritz Bunkus wrote:
> an audio packet corresponds to a video packet with timestamp 0. It also
> seems not so say what Opus needs it to say: that a number of samples
> have to be dropped because they're simply invalid.

Quoting from the first paragraph of Section 4.1: "Therefore, the first 
few samples produced by the decoder do not correspond to real input 
audio, but are instead composed of padding inserted by the encoder to 
compensate for this latency."

What do you think the text should say to make it clearer that "a number 
of samples have to be dropped because they're simply invalid"?

---

From: "Timothy B. Terriberry" <[email-masked]>
Date: Mon, 08 Jul 2013 11:26:14 -0700

Moritz Bunkus wrote:
> I think you misunderstood me. I did not mean to say that the Opus
> specs (any of them) should be changed. I only meant the wording in the
> _Matroska_ specs for the newly-introduced "CodecDelay" element[1]
> which, at the moment, reads as follows:
>
>> CodecDelay is the delay in nanoseconds to add to each Block timestamp.
>> The value should be small so the muxing of tracks with the same actual
>> timestamp are in the same Cluster.
>
> I think this wording is extremely misleading and does not really allow
> the use of this element to hold Opus' pre-skip value -- though it has
> been our intention to store just that in it.
>
> This is purely a matter internal to the Matroska team and specs and
> has nothing to do with any of the Opus RFCs and drafts.

Ah! Sorry for the noise, I did indeed confuse the antecedent. If you do 
find things that are unclear or that could be improved in the IETF 
drafts, please don't hesitate to let us know. More review is always 
appreciated.

> Kind regards,
> mosu
>
> [1] http://www.matroska.org/technical/specs/index.html