Re: [rtcweb] Codec Draft

Bernard Aboba <> Wed, 09 November 2011 00:49 UTC

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Subject: Re: [rtcweb] Codec Draft
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> So let me know: do you support that browsers must implement g729?
Simple answer:  No. We've been through the issues relating to G.729 in a number of other contexts, such as emergency service requirements (e.g. ECRIT Phone-BCP, NENA i3).  It didn't get in, even as OPTIONAL.  For example, here is what ECRIT PhoneBCP Section 14 says on the subject of audio codecs (end system requirements):

   ED-71 Endpoints MUST send and receive media streams on RTP [RFC3550].

   ED-72 Normal SIP offer/answer [RFC3264] negotiations MUST be used to
   agree on the media streams to be used.

   ED-73/SP-41 G.711 A law (and mu Law if they are intended be used in
   North America) encoded voice as described in [RFC3551] MUST be
   supported.  If the endpoint cannot support G.711, a transcoder MUST
   be used so that the offer received at the PSAP contains G.711.  It is
   desirable to include wideband codecs such as G.722 and AMR-WB in the
   offer.  PSAPs SHOULD support narrowband codecs common on endpoints in
   their area to avoid transcoding.

   ED-74 Silence suppression (Voice Activity Detection methods) MUST NOT
   be used on emergency calls.  Here is what NENA i3 stage 3 says (ESINet requirements): AudioAll User Agents in the ESInet must support g.711 mu-law and a-law. A-law support is required in the case that devices manufactured primarily for non-North American markets is used within North America. It is recommended that AMR, AMR-WB, EVRC[138], EVRC-B[139], EVRC-WB[140], and EVRC-NW[141] also be supported.