Re: [payload] draft-ietf-payload-rtp-opus-00 and specifying preference to receive stereo
Jean-Marc Valin <jmvalin@mozilla.com> Fri, 01 March 2013 21:56 UTC
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Date: Fri, 01 Mar 2013 16:56:13 -0500
From: Jean-Marc Valin <jmvalin@mozilla.com>
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To: Roman Shpount <roman@telurix.com>
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Subject: Re: [payload] draft-ietf-payload-rtp-opus-00 and specifying preference to receive stereo
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 03/01/2013 04:15 PM, Roman Shpount wrote: > I am sure someone have already asked this, but why do we need > "stereo" optional parameter and always specify number of channels 2 > in RTP map? Can this be replaced by simply saying that receiver > specifies its preference to receive stereo by specifying 2 channels > in RTP map and its preference to receive mono audio by specifying 1 > channel in RTP map? We should still specify that every receiver > MUST be able to receive and decode stereo signals. One of the reasons is preventing interop an failure case where one client would have opus/48000/1 while the other has opus/48000/2. It also makes it easier to negotiate the case where stereo is used in one direction, while mono is used in the other direction. The idea is that stereo=0 really means "stereo isn't useful for me" rather than "this stream cannot have stereo in it". There are applications where one might want to send stereo to a client that specified mono, for example, in conferencing applications where we want to send the same audio to all participants, or even for "high-quality music on hold" when we only want a single version of our music. In general, any opus stream may contain 48 kHz stereo in it, and that's why it's advertised as such. Jean-Marc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.13 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJRMSP9AAoJEJ6/8sItn9q9YFoIAKRxZN2MUp5M0F+R9e8SRPZF ZpSkjDec3/FmjLvRpe/pphb3CeWossvf6R2PzvOAPM9NWLgRS+70MEi0L/s6hEqS 0uZ6CpJuXc2+IT0VgL/+jdOPH/cWXlA4cSjQx3IgWM0lPBsba311g5Tan7io0E0c sPdIf9eY9oeVeCJXhnA0MiJ/yXwAcGRlHJ606NQ/T+QoyPBZb03+C98EVXfdHKai bfgIjGopqnzVPDfrmsYC75Lcpn0ZofcKBiEshXc4uHhUTTJsoipfDn4iPHz0UHBW W+SSs9xNBw+zOkxvmqsBFO8zsMoqoJMljTHbzIb5GDui9V9M946rgccUKBrvWJc= =x4fH -----END PGP SIGNATURE-----
- [payload] draft-ietf-payload-rtp-opus-00 and spec… Roman Shpount
- Re: [payload] draft-ietf-payload-rtp-opus-00 and … Jean-Marc Valin