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 <bigpe...@gmail.com> 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 _______________________________________________ codec mailing list codec@ietf.org https://www.ietf.org/mailman/listinfo/codec
