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Re: Issue 160: WebRTC 1.0 compatibility: support for p-time

From: Bernard Aboba <Bernard.Aboba@microsoft.com>
Date: Sun, 30 Nov 2014 00:35:55 +0000
To: "public-ortc@w3.org" <public-ortc@w3.org>
Message-ID: <BLUPR03MB133E891090C1DAD16F40289EC7C0@BLUPR03MB133.namprd03.prod.outlook.com>
[BA] Magnus provides a summary of ptime support in various codecs here: 
https://www.ietf.org/mail-archive/web/rtcweb/current/msg11485.html

Recommendations from https://tools.ietf.org/html/draft-ietf-rtcweb-jsep 
(only text from Section 5.2.1 Initial Offers is included but there is similar text relating to Answers): 

Each m= section MUST include the following attribute lines:
...
o For each supported codec, "a=rtpmap" and "a=fmtp" lines, as
specified in [RFC4566], Section 6. For audio, the codecs
specified in [I-D.ietf-rtcweb-audio], Section 3, MUST be be
supported.

o If this m= section is for media with configurable frame sizes,
e.g. audio, an "a=maxptime" line, indicating the smallest of the
maximum supported frame sizes out of all codecs included above, as
specified in [RFC4566], Section 6."

[BA] From this, it seems like there are several possibilities: 

1. Directly add ptime support to RTCRtpCodecCapability and RTCRtpCodecParameters as follows: 

partial dictionary RTCRtpCodecCapability {
    sequence unsigned long ptime; 
};

partial dictionary RTCRtpCodecParameters {
    unsigned long             ptime; 
};

2. Add ptime to the parameters defined in RTCRtpCodecCapability and RTCRtpCodecParameters: 

partial dictionary RTCRtpCodecCapability {
    Dictionary                parameters;
    Dictionary                options;
};

partial dictionary RTCRtpCodecParameters {
    Dictionary                parameters;
};


3.  Allow maxptime to be configured with RTCRtpParameters: 

partial dictionary RTCRtpParameters {
    unsigned long   maxptime; 
};

Peter  Thatcher said: 

"Should we just put this in RtpCodecParameters.parameters, or should we have
a specific RtpCodecParameters.ptime?  Or do we want .minptime and .maxptime?"
Received on Sunday, 30 November 2014 00:36:25 UTC

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