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

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?"

[BA] As noted in Magnus' summary, there are codec-specific ptime capabilities and settings that would be discovered in RtpCodecCapability.parameters and set in RtpCodecParameters.parameters. 
However, since the JSEP draft requires " an "a=maxptime" line, indicating the smallest of the maximum supported frame sizes out of all codecs included" it would be useful to have RtpCodecCapability.maxptime and RtpCodecParameters.maxptime so as to make it possible to discover a codec's maxptime, configure it and then compute the smallest of the maxptime values for all codecs.  


-----Original Message-----
From: Bernard Aboba 
Sent: Saturday, November 29, 2014 4:36 PM
To: public-ortc@w3.org
Subject: Re: Issue 160: WebRTC 1.0 compatibility: support for p-time

[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 Tuesday, 9 December 2014 17:45:03 UTC