Subject: [MEDIACTRL] XCON alignment:codecs and video layouts

From: "McGlashan, Scott" <[email-masked]>
Date: Thu, 20 Mar 2008 11:57:40 +0000

We discussed at the Philly meeting how we can align our work with XCON, specifically the data model (the current version is 09: http://www.ietf.org/internet-drafts/draft-ietf-xcon-common-data-model-09.txt). Two particular issues need to be addressed for the next data model draft (which XCON wants wrapped up asap).

[1] <codec> element. In the next data model draft it is proposed to add a <subtype> element (e.g. H264, etc) to the <codec> element and a mechanism by which further information about the codec can be specified. Assuming that the ivr and conferencing package supports auditing of their codec support on the MS (this is related to the discussion about how an AS can appropriately modify the SDP when running as a B2BUA between UA and MS, so a conference or connection is available before a join/dialogstart), then this issue is relevant to us. So I have 2 questions:

1A. What additional information about a codec - beyond the subtype - is relevant to the MS and AS in the mediaCtrl context? Audio codecs are probably more straightforward than video since video codecs may need to specify parameters like size, frame rate, I-frame interval, etc. So: is there information we need to capture in <codec> that goes beyond the subtype? Has someone else (e.g. mmusic?) defined that information?

1B. Any insight into format (XML, RDF, etc) for specifying additional codec information? CC/PP (http://www.w3.org/TR/CCPP-struct-vocab/) was discussed as one possibility but it is in RDF rather than XML format. Are there any others? The fallback would be custom XML elements.

[2] <video-layout> element. In the meeting we discussed that the conferencing package would support prefined video layouts and that we could re-use the XCONs ones. So: are the XCON predefined layout adequate for us? Are there layouts we should add or remove? The XCON layouts are described in the Data model spec, Section 4.2.11:

           +  single-view: Only one stream is presented by the focus to
            all participants in one panel.
         +  dual-view: This dual view option will present the video
            side-by-side in 2 panels and not alter the aspect ratio of
            the streams.  This will require the focus to introduce
            blanking on parts of the overall image as viewed by the
            participants.
         +  dual-view-crop: This side-by-side layout option instructs
            the focus to alter the aspect ratio of the streams (alter-
            aspect-ratio=TRUE) so that blanking is not necessary.  The
            focus handles the cropping of the streams.
         +  dual-view-2x1: This layout option instructs the focus to
            place one stream above the other, in essence with two rows
            and one column.  In this option the aspect ratio is not
            altered and blanking is introduced.
         +  dual-view-2x1-crop: This layout option also instructs the
            focus to place one stream above the other, in essence with
            two rows and one column.  In this option the aspect ratio is
            altered and the video streams are cropped.
         +  quad-view: Four equal-sized panels in a 2x2 layout is
            presented by the focus to all participants.  Typically the
            aspect ratio of the streams are maintained (alter-aspect-
            ratio= FALSE).
         +  multiple-3x3: Nine equal-sized panels in a 3x3 layout is
            presented by the focus to all participants.  Typically the
            aspect ratio of the streams are preserved.
         +  multiple-4x4: Sixteen equal-sized panels in a 4x4 layout is
            presented by the focus to all participants.  Typically the
            aspect ratio of the streams are preserved.
         +  multiple-5x1: This option refers to a 5x1 layout where one
            panel will occupy 4/9 of the mixed video stream while the
            others will each occupy 1/9 of the stream.  Typically the
            aspect ratio of the streams is preserved.
         +  automatic: This option allows the focus to add panels as
            streams are added.

Thanks

Scott

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