Need a bitrate definition #267

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alvestrand opened this Issue Aug 20, 2015 · 5 comments

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@alvestrand
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#254 defines a max bitrate, but there isn't a definition for the term in the spec. Need to point to one (preferably one that the IETF agrees is relevant).

@alvestrand
Contributor

One possibility is to reuse the TIAS definition from RFC 3890 section 6.2.2.

Note that this definition doesn't say what period it's calculated over, nor does it say how to deal with undershoots and overshoots. If the IETF can live without these parts of the definition, can the W3C do likewise?

@juberti
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juberti commented Aug 26, 2015

TIAS seems like the clear winner out of all the possible bitrate specifications. Agree the details can be left somewhat vague for now.

@aboba aboba was assigned by alvestrand Nov 19, 2015
@aboba
Contributor
aboba commented Nov 19, 2015

Here is some proposed text based on RFC 3890 Section 6.2.2:

The Transport Independent Application Specific Maximum (TIAS) bandwidth .... is the maximum [amount of bandwidth needed when all declared media streams are used] ... without counting IP or other transport layers like TCP or UDP.... This can be less than the sum of all the individual media streams values... [since] not all streams have their maximum at the same point in time.

@alvestrand
Contributor

The discussion at TPAC and IETF invoked the question of what timeframe we should look for a bitrate to be satisfied over - one second was proposed, but seemed to be thought a bit arbitrary. (Obviously it's not smooth at timescales less than the video frame size or audio packet time.)

@alvestrand alvestrand removed the TPAC topic label Nov 19, 2015
@aboba aboba added a commit that referenced this issue Nov 25, 2015
@aboba aboba Fix for Issue 267 f603624
@aboba aboba added the PR exists label Nov 25, 2015
@aboba
Contributor
aboba commented Nov 25, 2015

Left in the note about "TODO: Find or create a definition for bitrate (how much header overhead is included, for example). Should be aligned with RTCOutboundRTPStreamStats.targetBitrate in webrtc-stats.". Do we need another PR for targetBitrate?

@alvestrand alvestrand closed this Nov 25, 2015
@aboba aboba added a commit to w3c/ortc that referenced this issue Nov 28, 2015
@aboba aboba Fix for Issue 267 Bitrate definition
This is a fix for WebRTC 1.0 Issue 267:
w3c/webrtc-pc#267

Fixed in the following WebRTC 1.0 PR: 
w3c/webrtc-pc#401
b1f576d
@aboba aboba added a commit to w3c/ortc that referenced this issue Nov 28, 2015
@aboba aboba Added Issue 267 to changelog 3ca914f
@aboba aboba added a commit to w3c/ortc that referenced this issue Nov 28, 2015
@aboba aboba Add RFC 3890 to references
Relates to WebRTC 1.0 Issue 267: 
w3c/webrtc-pc#267
949ecd4
@aboba aboba referenced this issue in w3c/ortc Nov 28, 2015
Merged

Add RFC 3890 to references #287

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