RTCRtpHeaderExtensionParameters parameters #502

robin-raymond opened this Issue Apr 24, 2016 · 8 comments


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3 participants

dictionary RTCRtpHeaderExtensionParameters {
             DOMString      uri;
             unsigned short id;
             boolean        encrypt = false;
             Dictionary     parameters;

What parameters exist specific to a header ext URI?

aboba commented Apr 25, 2016

Parameters are defined in the specific header extension document. As an example, in https://tools.ietf.org/html/rfc6464 the "vad" extension attribute is defined (see Section 4):

It has a single extension attribute, named "vad". It takes the form
"vad=on" or "vad=off". If the header extension element is signaled
with "vad=on", the V bit described in Section 3 is in use, and MUST
be set by senders. If the header extension element is signaled with
"vad=off", the V bit is not in use, and its value MUST be ignored by
receivers. If the vad extension attribute is not specified, the
default is "vad=on".

An example attribute line in the Session Description Protocol (SDP)
for a conference might hence be:

  a=extmap:6 urn:ietf:params:rtp-hdrext:ssrc-audio-level vad=on

The vad extension attribute only controls the semantics of this
header extension attribute, and does not make any statement about
whether the sender is using any other voice activity detection
features, such as discontinuous transmission, comfort noise, or
silence suppression.

@aboba aboba added the question label Apr 25, 2016

9.14 RTP header extensions
boolean vad uses it.


Why would someone set this to false for vad? Why would someone turn this off?


Either add as a capability too, or we should not have this parameter.

@aboba aboba self-assigned this Jul 13, 2016

TODO: Add note that no existing implementation does this at this time but do nothing.


... and we did not find a good use case for it...

@aboba aboba added a commit that referenced this issue Jul 14, 2016
@aboba aboba RTCRtpHeaderExtensionParameters parameters
Fix for Issue #502
aboba commented Jul 21, 2016

TODO: Remove it.


Fixed by adding note that we did not find any use beyond "vad" V bit for the parameters header extension thus its use is not clear.

@aboba aboba was unassigned by dontcallmedom Aug 23, 2016
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