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Re: Opus implementation

From: Ralph Giles <giles@thaumas.net>
Date: Mon, 24 Sep 2012 12:29:22 -0700
Message-ID: <5060B492.6020709@thaumas.net>
To: Alexey Aylarov <alexey@zingaya.com>
CC: "public-webrtc@w3.org" <public-webrtc@w3.org>, "Cullen Jennings (fluffy)" <fluffy@cisco.com>
On 12-09-24 11:59 AM, Alexey Aylarov wrote:

> As I understand Opus was only discussed as a solution for wideband audio
> so farů

Opus supports narrowband as well as wideband (and several bandwidth
steps in-between). The sender side can configure the encoder to use this
mode. The reference encoder will also switch to narrowband automatically
when a appropriately low bitrate is requested.

The RTP payload draft[*] defines a maxcodedaudiobandwidth SDP parameter
the receiver can use to indicate a preference for narrowband. However,
because all of this is dynamically switchable in Opus, it is recommended
that receivers always implement fullband unless they have a specific
hardware limitation which prevents supporting that. In that case they
can take advantage of higher quality audio when appropriate, while still
scaling down to narrowband when that's what the sender ends up encoding.


[*] http://tools.ietf.org/html/draft-spittka-payload-rtp-opus
Received on Monday, 24 September 2012 19:29:52 UTC

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