Updates to the Opus Audio Codec
draft-ietf-codec-opus-update-03

The information below is for an old version of the document
Document Type Active Internet-Draft (codec WG)
Last updated 2016-09-01
Replaces draft-valin-codec-opus-update
Stream IETF
Intended RFC status (None)
Formats plain text pdf html bibtex
Stream WG state WG Document (wg milestone: Feb 2017 - Error and bugfix upd... )
Document shepherd No shepherd assigned
IESG IESG state I-D Exists
Consensus Boilerplate Unknown
Telechat date
Responsible AD (None)
Send notices to (None)
Network Working Group                                          JM. Valin
Internet-Draft                                       Mozilla Corporation
Intended status: Standards Track                                  K. Vos
Expires: March 5, 2017                                           vocTone
                                                       September 1, 2016

                    Updates to the Opus Audio Codec
                    draft-ietf-codec-opus-update-03

Abstract

   This document addresses minor issues that were found in the
   specification of the Opus audio codec in RFC 6716 [RFC6716].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 5, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Valin & Vos               Expires March 5, 2017                 [Page 1]
Internet-Draft                 Opus Update                September 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Stereo State Reset in SILK  . . . . . . . . . . . . . . . . .   2
   4.  Parsing of the Opus Packet Padding  . . . . . . . . . . . . .   3
   5.  Resampler buffer  . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Integer wrap-around in inverse gain computation . . . . . . .   5
   7.  Integer wrap-around in LSF decoding . . . . . . . . . . . . .   6
   8.  Hybrid Folding  . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Downmix to Mono . . . . . . . . . . . . . . . . . . . . . . .   8
   10. New Test Vectors  . . . . . . . . . . . . . . . . . . . . . .   8
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   This document addresses minor issues that were discovered in the
   reference implementation of the Opus codec that serves as the
   specification in RFC 6716 [RFC6716].  Only issues affecting the
   decoder are listed here.  An up-to-date implementation of the Opus
   encoder can be found at http://opus-codec.org/. The updated
   specification remains fully compatible with the original
   specification.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

3.  Stereo State Reset in SILK

   The reference implementation does not reinitialize the stereo state
   during a mode switch.  The old stereo memory can produce a brief
   impulse (i.e. single sample) in the decoded audio.  This can be fixed
   by changing silk/dec_API.c at line 72:

Valin & Vos               Expires March 5, 2017                 [Page 2]
Internet-Draft                 Opus Update                September 2016

        for( n = 0; n < DECODER_NUM_CHANNELS; n++ ) {
            ret  = silk_init_decoder( &channel_state[ n ] );
        }
   +    silk_memset(&((silk_decoder *)decState)->sStereo, 0,
   +                sizeof(((silk_decoder *)decState)->sStereo));
   +    /* Not strictly needed, but it's cleaner that way */
   +    ((silk_decoder *)decState)->prev_decode_only_middle = 0;

        return ret;
    }

   This change affects the normative part of the decoder, although the
   amount of change is too small to make a significant impact on
   testvectors.

4.  Parsing of the Opus Packet Padding

   It was discovered that some invalid packets of very large size could
Show full document text