Hi Qin
The use of an out of range value within SDP to signal that you don't
want to accept something does not seem to be within the spirit of SDP.
The normal usage would be "I can do A, B, C" with an answer of "C".
In the case of QoE measurement - an RTP endpoint may incorporate one or
more QoE algorithms that are used to estimate the user perceived quality
of the received media stream. The offer should contain a subset of the
QoE algorithms supported by the offeror and the answer should contain a
subset of the QoE algorithms supported by the answerer; it is not
necessary that the QoE algorithms in the Answer are a subset of those in
the Offer (as the algorithms don't need to interoperate). Unlike the
case when negotiating a codec - it is not required that the two
endpoints implement the same algorithm although there is some minor
advantage if the two endpoints use the same algorithm if possible in
order that QoE scores for the two directions are equivalently scaled.
I'd prefer to use SDP in the following way:
(i) Offer provides a list of one or more QoE algorithms that it
supports, in the form of a map
(ii) Answer provides a list of one or more QoE algorithms that it
supports, in the form of a map. If the Answerer supports one of the same
algorithms that the Offer provides then the Answerer SHOULD answer with
only that algorithm however MAY answer with more than one.
I'll work out the appropriate text changes to implement this unless
there are strong technical reasons not to.
Regards
Alan
On 11/12/13, 9:14 PM, Qin Wu wrote:
Hi, Alan:
Thank for quick response. Here are additional changes I proposed.
Regarding section 4.1, I propose the following change:
OLD TEXT:
mapentry = "calg:" 1*5 DIGIT ["/" direction]
;Values other than 4095~4351 are valid
NEW TEXT:
mapentry = "calg:" 1*3 DIGIT ["/" direction]
;Values 1..255 are valid
OLD TEXT:
"
If the answerer wishes to reject a mosref attribute offered by the
offerer, it sets identifiers associated with segment extensions in
the answer to the value in the range 4096-4351.
"
NEW TEXT:
"
If the answerer wishes to reject a mosref attribute offered by the
offerer, it sets identifiers associated with segment extensions in
the answer to the value in the range 512-767.
"
OLD TEXT:
"
If a party wishes to offer mutually exclusive alternatives, then
multiple segment extensions with the same identifier in the
(unusable) range 4096-4351 MAY be offered;
"
NEW TEXT:
"
If a party wishes to offer mutually exclusive alternatives, then
multiple segment extensions with the same identifier in the
(unusable) range 512-767 MAY be offered;
"
OLD TEXT:
"
Similarly, if more segment extensions are offered than can be fit in
the valid range, identifiers in the range 4096-4351 MAY be offered;
"
NEW TEXT:
"
Similarly, if more segment extensions are offered than can be fit in
the valid range, identifiers in the range 512-767 MAY be offered;
"
OLD TEXT:
"
Note that the range 4096-4351 for these negotiation identifiers is
deliberately restricted to allow expansion of the range of valid
identifiers in future.
"
NEW TEXT:
"
Note that the range 512-767 for these negotiation identifiers is
deliberately restricted to allow expansion of the range of valid
identifiers in future.
"
Regards!
-Qin
*From:*[email protected] [mailto:[email protected]] *On
Behalf Of *Alan Clark
*Sent:* Wednesday, November 13, 2013 1:06 AM
*To:* Joel Halpern; A. Jean Mahoney; [email protected];
[email protected]; [email protected]
*Subject:* Re: [xrblock] [Gen-art] Review:
draft-ietf-xrblock-rtcp-xr-qoe-12
Hi Joel
Thanks for your comments.
(i) Section 1.4
Proposed change
The MOS Metrics Report Block can be used in any application of RTP
for which QoE measurement algorithms are defined.
to
The MOS Metrics Report Block can be used in any application of RTP
for which QoE (Quality of Experience) measurement algorithms are defined.
(ii) Section 3.2.2
Proposed change
"The 8-bit ID is the local identifier of this segment in the range
1-255 inclusive"
to
"The 8-bit CAID is the session specific reference to the calculation
algorithm and associated qualifiers indicated in SDP (see Section 4.1)
and used to compute QoE scores for this segment"
(iii) Section 3.2.1
Proposed change
"The 8-bit CAID is the local identifier of calculation algorithm
associated with this segment in the range 1-255 inclusive. "
to
"The 8-bit CAID is the session specific reference to the calculation
algorithm and associated qualifiers indicated in SDP (see Section 4.1)
and used to compute QoE scores for this segment"
(iv) Section 4.1
Proposed change
mapentry = "calg:" 1*5 DIGIT ["/" direction]
;Values other than 4095~4351 are valid
to
mapentry = "calg:" 1*3 DIGIT ["/" direction]
;Values other than 1..255 are valid
and remove
mostype = "mostype=" ("e"; Estimated MOS [P.800.1]
/"s";subjective MOS [P.800.1]
/"o";objective MOS [P.800.1]
/non-ws-string)
We will see if there are additional comments and then update the draft
Regards
Alan Clark
On 11/12/13, 7:12 AM, Joel Halpern wrote:
I am the assigned Gen-ART reviewer for this draft. For background on
Gen-ART, please see the FAQ at
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.
Please resolve these comments along with any other Last Call comments
you may receive.
Document: draft-ietf-xrblock-rtcp-xr-qoe-12
RTP Control Protocol (RTCP) Extended Report (XR) Blocks for
MOS Metric Reporting
Reviewer: Joel M. Halpern
Review Date: 12-November-2013
IETF LC End Date: 27-November-2013
IESG Telechat date: N/A
Summary: This document is nearly ready for publication as a
Proposed Standard RFC
Major issues:
Moderate issues:
In section 3.2.2 on Multi-Channel audio per SSRC Segment, the
format description for the Calculation Algorithm ID (CAID) reads:
"The 8-bit ID is the local identifier of this segment in the range
1-255 inclusive." I am pretty sure this is supposed to be an
algorithm ID, not a segment index?
The text in section 4.1 indicates that the number after
"calg:" in the mapentry of the calgextmap is used as the ID in the
CAID of the xrblock. The packet format only allows 8 bits of
value. So why does the SDP format allow up to 5 digits? Also, is
there some reason that the special values 4095-4351 (in section
4.1) or 4096-4351 (in section 4.2) are used rather than say
equally invalid 512 through some appropriate upper bound still in
3 digits?
Minor issues:
Please ensure that all acronyms are expanded on first use.
For example, QoE is not expanded.
The notes in B.3 indicate that mostype was to be removed from
the SDP grammar. But it is still defined. And section 4.2 still
mentions it, even though it does not get referenced by the message
format. Please finish removing it. (also "most type")
Nits/editorial comments:
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