The suggested text is indeed correct. The question is whether that
should go in an errata or in this draft that is already meant to update
RFC6716:
https://tools.ietf.org/html/draft-ietf-codec-opus-update-01
Cheers,
Jean-Marc
On 15/06/15 11:01 AM, RFC Errata System wrote:
> The following errata report has been submitted for RFC6716,
> "Definition of the Opus Audio Codec".
>
> --------------------------------------
> You may review the report below and at:
> http://www.rfc-editor.org/errata_search.php?rfc=6716&eid=4392
>
> --------------------------------------
> Type: Technical
> Reported by: Peter Budny <[email protected]>
>
> Section: 2
>
> Original Text
> -------------
> The Opus codec scales from 6 kbit/s narrowband mono speech to
> 510 kbit/s fullband stereo music, with algorithmic delays ranging
> from 5 ms to 65.2 ms.
>
> (further in the same section)
>
> To
> compensate for the different look-ahead required by each layer, the
> CELT encoder input is delayed by an additional 2.7 ms.
>
> Corrected Text
> --------------
> The Opus codec scales from 6 kbit/s narrowband mono speech to
> 510 kbit/s fullband stereo music, with algorithmic delays ranging
> from 5 ms to 66.5 ms.
>
> (further in the same section)
>
> To
> compensate for the different look-ahead required by each layer, the
> CELT encoder input is delayed by an additional 4 ms.
>
> Notes
> -----
> For the latter text, the delays for the CELT and SILK layers must match.
> SILK has a "5 ms look-ahead for noise shaping estimation", and "1.5 ms delay
> for sampling rate conversion", totaling 6.5 ms. CELT has a "2.5 ms
> look-ahead due to the overlapping MDCT windows". Thus, the amount of delay
> needed to align CELT with SILK is 6.5ms - 2.5ms = 4ms.
>
> The text at the beginning of the section must reflect this as well. The
> "algorithmic delays" reported apparently include framing (minimum frame size
> 2.5ms + look-ahead delay in CELT-only mode 2.5ms = 5ms). In that case, the
> maximum delay is the maximum frame size (60ms) + the maximum delay for
> look-ahead and resampling (6.5ms) = 66.5ms.
>
> Confirmed by author ("Jmvalin") at
> https://en.wikipedia.org/wiki/Talk:Opus_(audio_format)/Archive_1#Codec_delay_values
>
> Instructions:
> -------------
> This erratum is currently posted as "Reported". If necessary, please
> use "Reply All" to discuss whether it should be verified or
> rejected. When a decision is reached, the verifying party (IESG)
> can log in to change the status and edit the report, if necessary.
>
> --------------------------------------
> RFC6716 (draft-ietf-codec-opus-16)
> --------------------------------------
> Title : Definition of the Opus Audio Codec
> Publication Date : September 2012
> Author(s) : JM. Valin, K. Vos, T. Terriberry
> Category : PROPOSED STANDARD
> Source : Internet Wideband Audio Codec RAI
> Area : Real-time Applications and Infrastructure
> Stream : IETF
> Verifying Party : IESG
>
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