draft-ietf-rtcweb-audio-09.txt		draft-ietf-rtcweb-audio-10.txt
	Network Working Group JM. Valin		Network Working Group JM. Valin
	Internet-Draft Mozilla		Internet-Draft Mozilla
	Intended status: Standards Track C. Bran		Intended status: Standards Track C. Bran
	Expires: May 8, 2016 Plantronics		Expires: August 12, 2016 Plantronics
	November 5, 2015		February 9, 2016
	WebRTC Audio Codec and Processing Requirements		WebRTC Audio Codec and Processing Requirements
	draft-ietf-rtcweb-audio-09		draft-ietf-rtcweb-audio-10
	Abstract		Abstract
	This document outlines the audio codec and processing requirements		This document outlines the audio codec and processing requirements
	for WebRTC endpoints.		for WebRTC endpoints.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
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	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on May 8, 2016.		This Internet-Draft will expire on August 12, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2016 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
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	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
	3. Codec Requirements . . . . . . . . . . . . . . . . . . . . . 2		3. Codec Requirements . . . . . . . . . . . . . . . . . . . . . 2
	4. Audio Level . . . . . . . . . . . . . . . . . . . . . . . . . 3		4. Audio Level . . . . . . . . . . . . . . . . . . . . . . . . . 3
	5. Acoustic Echo Cancellation (AEC) . . . . . . . . . . . . . . 4		5. Acoustic Echo Cancellation (AEC) . . . . . . . . . . . . . . 4
	6. Legacy VoIP Interoperability . . . . . . . . . . . . . . . . 5		6. Legacy VoIP Interoperability . . . . . . . . . . . . . . . . 5
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 5		8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
	9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5		9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
	10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
	10.1. Normative References . . . . . . . . . . . . . . . . . . 6		10.1. Normative References . . . . . . . . . . . . . . . . . . 6
	10.2. Informative References . . . . . . . . . . . . . . . . . 6		10.2. Informative References . . . . . . . . . . . . . . . . . 6
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
	1. Introduction		1. Introduction
	An integral part of the success and adoption of the Web Real Time		An integral part of the success and adoption of the Web Real Time
	Communications (WebRTC) will be the voice and video interoperability		Communications (WebRTC) will be the voice and video interoperability
	between WebRTC applications. This specification will outline the		between WebRTC applications. This specification will outline the
	audio processing and codec requirements for WebRTC endpoint		audio processing and codec requirements for WebRTC endpoints.
	implementations.
	2. Terminology		2. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in RFC		"OPTIONAL" in this document are to be interpreted as described in RFC
	2119 [RFC2119].		2119 [RFC2119].
	3. Codec Requirements		3. Codec Requirements
	To ensure a baseline level of interoperability between WebRTC		To ensure a baseline level of interoperability between WebRTC
	endpoints, a minimum set of required codecs are specified below. If		endpoints, a minimum set of required codecs are specified below. If
	other suitable audio codecs are available for the browser to use, it		other suitable audio codecs are available for the WebRTC endpoint to
	is RECOMMENDED that they are also be included in the offer in order		use, it is RECOMMENDED that they are also be included in the offer in
	to maximize the possibility to establish the session without the need		order to maximize the possibility to establish the session without
	for audio transcoding.		the need for audio transcoding.
	WebRTC endpoints are REQUIRED to implement the following audio		WebRTC endpoints are REQUIRED to implement the following audio
	codecs:		codecs:
	o Opus [RFC6716] with the payload format specified in		o Opus [RFC6716] with the payload format specified in
	[I-D.ietf-payload-rtp-opus].		[I-D.ietf-payload-rtp-opus].
	o G.711 PCMA and PCMU with the payload format specified in section		o G.711 PCMA and PCMU with the payload format specified in section
	4.5.14 of [RFC3551].		4.5.14 of [RFC3551].
	o [RFC3389] comfort noise (CN). Receivers MUST support RFC3389 CN		o [RFC3389] comfort noise (CN). WebRTC endpoints MUST support
	for streams encoded with G.711 or any other supported codec that		RFC3389 CN for streams encoded with G.711 or any other supported
	does not provide its own CN. Since Opus provides its own CN		codec that does not provide its own CN. Since Opus provides its
	mechanism, the use of RFC3389 CN with Opus is NOT RECOMMENDED.		own CN mechanism, the use of RFC3389 CN with Opus is NOT
	Use of DTX/CN by senders is OPTIONAL.		RECOMMENDED. Use of DTX/CN by senders is OPTIONAL.
	o The audio/telephone-event media format as specified in [RFC4733].		o The audio/telephone-event media format as specified in [RFC4733].
	WebRTC endpoints are REQUIRED to be able to generate and consume		The endpoints MAY send DTMF events at any time and SHOULD suppress
	the following events:		in-band DTMF tones, if any. WebRTC endpoints are REQUIRED to be
			able to generate and consume the following events:
	+------------+--------------------------------+-----------+		+------------+--------------------------------+-----------+
	|Event Code | Event Name | Reference |		|Event Code | Event Name | Reference |
	+------------+--------------------------------+-----------+		+------------+--------------------------------+-----------+
	| 0 | DTMF digit "0" | RFC4733 |		| 0 | DTMF digit "0" | RFC4733 |
	| 1 | DTMF digit "1" | RFC4733 |		| 1 | DTMF digit "1" | RFC4733 |
	| 2 | DTMF digit "2" | RFC4733 |		| 2 | DTMF digit "2" | RFC4733 |
	| 3 | DTMF digit "3" | RFC4733 |		| 3 | DTMF digit "3" | RFC4733 |
	| 4 | DTMF digit "4" | RFC4733 |		| 4 | DTMF digit "4" | RFC4733 |
	| 5 | DTMF digit "5" | RFC4733 |		| 5 | DTMF digit "5" | RFC4733 |
	| 6 | DTMF digit "6" | RFC4733 |		| 6 | DTMF digit "6" | RFC4733 |
	| 7 | DTMF digit "7" | RFC4733 |		| 7 | DTMF digit "7" | RFC4733 |
	| 8 | DTMF digit "8" | RFC4733 |		| 8 | DTMF digit "8" | RFC4733 |
	| 9 | DTMF digit "9" | RFC4733 |		| 9 | DTMF digit "9" | RFC4733 |
	| 10 | DTMF digit "*" | RFC4733 |		| 10 | DTMF digit "*" | RFC4733 |
	| 11 | DTMF digit "#" | RFC4733 |		| 11 | DTMF digit "#" | RFC4733 |
			| 12 | DTMF digit "A" | RFC4733 |
			| 13 | DTMF digit "B" | RFC4733 |
			| 14 | DTMF digit "C" | RFC4733 |
			| 15 | DTMF digit "D" | RFC4733 |
	+------------+--------------------------------+-----------+		+------------+--------------------------------+-----------+
	For all cases where the endpoint is able to process audio at a		For all cases where the endpoint is able to process audio at a
	sampling rate higher than 8 kHz, it is RECOMMENDED that Opus be		sampling rate higher than 8 kHz, it is RECOMMENDED that Opus be
	offered before PCMA/PCMU. For Opus, all modes MUST be supported on		offered before PCMA/PCMU. For Opus, all modes MUST be supported on
	the decoder side. The choice of encoder-side modes is left to the		the decoder side. The choice of encoder-side modes is left to the
	implementer. Endpoints MAY use the offer/answer mechanism to signal		implementer. Endpoints MAY use the offer/answer mechanism to signal
	a preference for a particular mode or ptime.		a preference for a particular mode or ptime.
	For additional information on implementing codecs other than the		For additional information on implementing codecs other than the
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	5. Acoustic Echo Cancellation (AEC)		5. Acoustic Echo Cancellation (AEC)
	It is plausible that the dominant near to mid-term WebRTC usage model		It is plausible that the dominant near to mid-term WebRTC usage model
	will be people using the interactive audio and video capabilities to		will be people using the interactive audio and video capabilities to
	communicate with each other via web browsers running on a notebook		communicate with each other via web browsers running on a notebook
	computer that has built-in microphone and speakers. The notebook-as-		computer that has built-in microphone and speakers. The notebook-as-
	communication-device paradigm presents challenging echo cancellation		communication-device paradigm presents challenging echo cancellation
	problems, the specific remedy of which will not be mandated here.		problems, the specific remedy of which will not be mandated here.
	However, while no specific algorithm or standard will be required by		However, while no specific algorithm or standard will be required by
	WebRTC compatible endpoints, echo cancellation will improve the user		WebRTC-compatible endpoints, echo cancellation will improve the user
	experience and should be implemented by the endpoint device.		experience and should be implemented by the endpoint device.
	WebRTC endpoints SHOULD include an AEC or some other form of echo		WebRTC endpoints SHOULD include an AEC or some other form of echo
	control. On general purpose platforms (e.g. PC), it is common for		control. On general purpose platforms (e.g. PC), it is common for
	the audio capture ADC and the audio playback DAC to use different		the audio capture ADC and the audio playback DAC to use different
	clocks. In these cases, such as when a webcam is used for capture		clocks. In these cases, such as when a webcam is used for capture
	and a separate soundcard is used for playback, the sampling rates are		and a separate soundcard is used for playback, the sampling rates are
	likely to differ slightly. Endpoint AECs SHOULD be robust to such		likely to differ slightly. Endpoint AECs SHOULD be robust to such
	conditions, unless they are shipped along with hardware that		conditions, unless they are shipped along with hardware that
	guarantees capture and playback to be sampled from the same clock.		guarantees capture and playback to be sampled from the same clock.
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	typically used in NLPs. Similarly, endpoints SHOULD have the ability		typically used in NLPs. Similarly, endpoints SHOULD have the ability
	to detect the presence of a headset and disable echo cancellation.		to detect the presence of a headset and disable echo cancellation.
	For some applications where the remote endpoint may not have an echo		For some applications where the remote endpoint may not have an echo
	canceller, the local endpoint MAY include a far-end echo canceller,		canceller, the local endpoint MAY include a far-end echo canceller,
	but if that is the case, it SHOULD be disabled by default.		but if that is the case, it SHOULD be disabled by default.
	6. Legacy VoIP Interoperability		6. Legacy VoIP Interoperability
	The codec requirements above will ensure, at a minimum, voice		The codec requirements above will ensure, at a minimum, voice
	interoperability capabilities between WebRTC endpoints applications		interoperability capabilities between WebRTC endpoints and legacy
	and legacy phone systems that support G.711.		phone systems that support G.711.
	7. IANA Considerations		7. IANA Considerations
	This document makes no request of IANA.		This document makes no request of IANA.
	Note to RFC Editor: this section may be removed on publication as an		Note to RFC Editor: this section may be removed on publication as an
	RFC.		RFC.
	8. Security Considerations		8. Security Considerations
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