A system, comprising: one or more media processing nodes, each configured to accept from a plurality of participants to a video conference a plurality of audio and video streams from a plurality of video conference endpoints each associated with one of the plurality of participants, wherein the plurality of video conference endpoints belong to different communication services provided by different vendors, characterised in that: each of the media processing nodes is further configured to build up a composite metadata field associated with the composite video stream in order to apply operations outlined in the metadata field to each of the audio and video streams of the composite video stream and each of the media processing nodes utilizes information from the composite metadata field for efficient transcoding and processing of the associated composite audio and video streams; for each of the plurality of participants to the video conference, convert and compose the plurality of audio and video streams into one or more composite video and audio streams compatible with the video conference endpoint associated with the participant in real time; and render the composite video and audio stream compatible with the video conference endpoint associated with each of the plurality of participants to the video conference, wherein the different communication services to which the plurality of video conference endpoints belong are transparent to the plurality of participants. one or more media processing nodes, each configured to accept from a plurality of participants to a video conference a plurality of audio and video streams from a plurality of video conference endpoints each associated with one of the plurality of participants, wherein the plurality of video conference endpoints belong to different communication services provided by different vendors, characterised in that: each of the media processing nodes is further configured to build up a composite metadata field associated with the composite video stream in order to apply operations outlined in the metadata field to each of the audio and video streams of the composite video stream and each of the media processing nodes utilizes information from the composite metadata field for efficient transcoding and processing of the associated composite audio and video streams; for each of the plurality of participants to the video conference, convert and compose the plurality of audio and video streams into one or more composite video and audio streams compatible with the video conference endpoint associated with the participant in real time; and render the composite video and audio stream compatible with the video conference endpoint associated with each of the plurality of participants to the video conference, wherein the different communication services to which the plurality of video conference endpoints belong are transparent to the plurality of participants. accept from a plurality of participants to a video conference a plurality of audio and video streams from a plurality of video conference endpoints each associated with one of the plurality of participants, wherein the plurality of video conference endpoints belong to different communication services provided by different vendors, characterised in that: each of the media processing nodes is further configured to build up a composite metadata field associated with the composite video stream in order to apply operations outlined in the metadata field to each of the audio and video streams of the composite video stream and each of the media processing nodes utilizes information from the composite metadata field for efficient transcoding and processing of the associated composite audio and video streams; for each of the plurality of participants to the video conference, convert and compose the plurality of audio and video streams into one or more composite video and audio streams compatible with the video conference endpoint associated with the participant in real time; and render the composite video and audio stream compatible with the video conference endpoint associated with each of the plurality of participants to the video conference, wherein the different communication services to which the plurality of video conference endpoints belong are transparent to the plurality of participants.