A method for transmitting at least two video streams, each of the at least two video streams carrying encoded video data, the encoded video data respectively carried by the at least two video streams being decodable independently from each other, the method comprising: sending a Session Description Protocol, SDP, description of video streams of a plurality of video streams including the at least two video streams; in response to sending the SDP description, receiving a request for obtaining the at least two video streams; transmitting the at least two video streams according to the received request, wherein the SDP description comprises a session level section and a plurality of media level sections for each of the plurality of video streams, wherein the session level section comprises an SDP group attribute to indicate a spatial relationship, within a same shared spatial reference frame, between video data carried by the at least two video streams; wherein the SDP group attribute comprises video stream grouping information; wherein the video stream grouping information comprises a set of identifiers of video streams of the plurality of video streams and a group semantic signalling that video data carried by the identified video streams have a spatial relationship, the set of identifiers comprising at least an identifier of each of the at least two video streams; and wherein the SDP description further comprises, in the media level section for each of the at least two video streams, the identifier of the video stream and an SDP spatial relationship attribute to provide location information of the video data carried by the corresponding video stream within the same shared spatial reference frame. sending a Session Description Protocol, SDP, description of video streams of a plurality of video streams including the at least two video streams; in response to sending the SDP description, receiving a request for obtaining the at least two video streams; transmitting the at least two video streams according to the received request, wherein the SDP description comprises a session level section and a plurality of media level sections for each of the plurality of video streams, wherein the session level section comprises an SDP group attribute to indicate a spatial relationship, within a same shared spatial reference frame, between video data carried by the at least two video streams; wherein the SDP group attribute comprises video stream grouping information; wherein the video stream grouping information comprises a set of identifiers of video streams of the plurality of video streams and a group semantic signalling that video data carried by the identified video streams have a spatial relationship, the set of identifiers comprising at least an identifier of each of the at least two video streams; and wherein the SDP description further comprises, in the media level section for each of the at least two video streams, the identifier of the video stream and an SDP spatial relationship attribute to provide location information of the video data carried by the corresponding video stream within the same shared spatial reference frame. wherein the SDP description comprises a session level section and a plurality of media level sections for each of the plurality of video streams, wherein the session level section comprises an SDP group attribute to indicate a spatial relationship, within a same shared spatial reference frame, between video data carried by the at least two video streams; wherein the SDP group attribute comprises video stream grouping information; wherein the video stream grouping information comprises a set of identifiers of video streams of the plurality of video streams and a group semantic signalling that video data carried by the identified video streams have a spatial relationship, the set of identifiers comprising at least an identifier of each of the at least two video streams; and wherein the SDP description further comprises, in the media level section for each of the at least two video streams, the identifier of the video stream and an SDP spatial relationship attribute to provide location information of the video data carried by the corresponding video stream within the same shared spatial reference frame.