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<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE rfc SYSTEM 'rfc2629.dtd' [
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<!ENTITY rfc6716 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6716.xml'>
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<?rfc toc="yes" symrefs="yes" ?>
<rfc ipr="trust200902" category="std" docName="draft-ietf-codec-oggopus-14"
updates="5334">
<front>
<title abbrev="Ogg Opus">Ogg Encapsulation for the Opus Audio Codec</title>
<author initials="T.B." surname="Terriberry" fullname="Timothy B. Terriberry">
<organization>Mozilla Corporation</organization>
<address>
<postal>
<street>650 Castro Street</street>
<city>Mountain View</city>
<region>CA</region>
<code>94041</code>
<country>USA</country>
</postal>
<phone>+1 650 903-0800</phone>
<email>tterribe@xiph.org</email>
</address>
</author>
<author initials="R." surname="Lee" fullname="Ron Lee">
<organization>Voicetronix</organization>
<address>
<postal>
<street>246 Pulteney Street, Level 1</street>
<city>Adelaide</city>
<region>SA</region>
<code>5000</code>
<country>Australia</country>
</postal>
<phone>+61 8 8232 9112</phone>
<email>ron@debian.org</email>
</address>
</author>
<author initials="R." surname="Giles" fullname="Ralph Giles">
<organization>Mozilla Corporation</organization>
<address>
<postal>
<street>163 West Hastings Street</street>
<city>Vancouver</city>
<region>BC</region>
<code>V6B 1H5</code>
<country>Canada</country>
</postal>
<email>giles@xiph.org</email>
</address>
</author>
<date day="22" month="February" year="2016"/>
<area>RAI</area>
<workgroup>codec</workgroup>
<abstract>
<t>
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.
</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<t>
The IETF Opus codec is a low-latency audio codec optimized for both voice and
general-purpose audio.
See <xref target="RFC6716"/> for technical details.
This document defines the encapsulation of Opus in a continuous, logical Ogg
bitstream <xref target="RFC3533"/>.
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.
</t>
<t>
Ogg bitstreams are made up of a series of 'pages', each of which contains data
from one or more 'packets'.
Pages are the fundamental unit of multiplexing in an Ogg stream.
Each page is associated with a particular logical stream and contains a capture
pattern and checksum, flags to mark the beginning and end of the logical
stream, and a 'granule position' that represents an absolute position in the
stream, to aid seeking.
A single page can contain up to 65,025 octets of packet data from up to 255
different packets.
Packets can be split arbitrarily across pages, and continued from one page to
the next (allowing packets much larger than would fit on a single page).
Each page contains 'lacing values' that indicate how the data is partitioned
into packets, allowing a demultiplexer (demuxer) to recover the packet
boundaries without examining the encoded data.
A packet is said to 'complete' on a page when the page contains the final
lacing value corresponding to that packet.
</t>
<t>
This encapsulation defines the contents of the packet data, including
the necessary headers, the organization of those packets into a logical
stream, and the interpretation of the codec-specific granule position field.
It does not attempt to describe or specify the existing Ogg container format.
Readers unfamiliar with the basic concepts mentioned above are encouraged to
review the details in <xref target="RFC3533"/>.
</t>
</section>
<section anchor="terminology" title="Terminology">
<t>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
"SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in <xref target="RFC2119"/>.
</t>
</section>
<section anchor="packet_organization" title="Packet Organization">
<t>
An Ogg Opus stream is organized as follows (see
<xref target="packet-org-example"/> for an example).
<figure anchor="packet-org-example"
title="Example packet organization for a logical Ogg Opus stream"
align="center">
<artwork align="center"><![CDATA[
Page 0 Pages 1 ... n Pages (n+1) ...
+------------+ +---+ +---+ ... +---+ +-----------+ +---------+ +--
| | | | | | | | | | | | |
|+----------+| |+-----------------+| |+-------------------+ +-----
|||ID Header|| || Comment Header || ||Audio Data Packet 1| | ...
|+----------+| |+-----------------+| |+-------------------+ +-----
| | | | | | | | | | | | |
+------------+ +---+ +---+ ... +---+ +-----------+ +---------+ +--
^ ^ ^
| | |
| | Mandatory Page Break
| |
| ID header is contained on a single page
|
]]></artwork>
</figure>
<t>
There are two mandatory header packets.
The first packet in the logical Ogg bitstream MUST contain the identification
(ID) header, which uniquely identifies a stream as Opus audio.
The format of this header is defined in <xref target="id_header"/>.
It is placed alone (without any other packet data) on the first page of
the logical Ogg bitstream, and completes on that page.
This page has its 'beginning of stream' flag set.
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