Re: [rtcweb] SDP testing

[Matthew Kaufman <[e-mail]>]

On 10/20/2012 4:20 PM, Bernard Aboba wrote:
> Harald said:
>
> "Thanks for the info - can you point to the bugs you filed on these 
> issues with our implementation? I'll try to see that they're followed up."
>
> [BA] To determine whether something is a "bug" or a "feature" it helps 
> to have a specification that states what is expected.  Since we're 
> primarily talking about SDP usage within the API rather than what 
> travels over the wire (after all, signaling is out of scope in 
> WebRTC), http://tools.ietf.org/html/draft-nandakumar-rtcweb-sdp is 
> only a baby step toward determining whether the SDP output by 
> createOffer is conformant or whether input to setLocalDescription or 
> setRemoteDescription should be acceptable or not, and if not, what 
> should happen.
>

Precisely the problem. It isn't a "bug" with the Google Chrome beta. It 
is a "bug" with the current specification, which says "see SDP O/A RFC" 
rather than "this is what a browser must allow" or even "this is the 
type of error a browser must throw if the rules aren't followed".

I'll pick some choice examples from some SDP that the latest Chrome beta 
just gave me from createOffer (without pasting the entire blob it 
disgorges):


s=-

Can I add "e=[e-mail]" right after this?

How about a "p=" line?

a=group:BUNDLE audio video

Can I remove this before passing it back to setLocal Description?

a=ice-options:google-ice

How about removing this? Or changing it to 
"a=ice-options:matthew-special-ice"?

a=sendrecv

Can I change it to sendonly?

a=rtcp-mux

Remove this?

a=crypto:1 AES_CM_128_HMAC_SHA1_80 
inline:66AIWBQ/R+UnMc4N/NP/b2hjEB6ydFMMCc8n3DMp

Remove this? Change the key? Set up DTLS-SRTP instead?

a=rtpmap:103 ISAC/16000

Change this to rtpmap: 110 ISAC/16000 because I prefer 110 as the codec ID?

a=ssrc:1018881792 cname:B0VSPpORV75cCTIv

Delete this? Change the ssrc ID because I don't like this one? or the cname?

m=video 1 RTP/SAVPF 100 101 102 c=IN IP4 0.0.0.0

Change this to RTP/SAVP ? [Never mind that "IN IP4 0.0.0.0" is a strange 
thing to have coming from "createOffer"]

NOWHERE in the JSEP specification can I find the answers to these 
questions. That makes working out what is allowed a browser-by-browser 
exhaustive search, which is unacceptable.

Matthew Kaufman