Video decoder comprising: a decoding core configured to reconstruct a decoded picture from video coding units within an access unit, AU, of a video data stream to obtain a reconstructed version of the decoded picture, wherein the decoding core is configured to start decoding parts of a picture before receiving all parts of the picture; an in-loop filter configured to filter the reconstructed version of the decoded picture to obtain a filtered version of the decoded picture; and a parametrizer configured to parametrize the in-loop filter by: reading one or more filter coefficients for parametrizing the in-loop filter in terms of transfer function from a predetermined parameter set which follows, along data stream order, all of the video coding units and which is located within the access unit, AU, of the decoded picture; reading spatially selective in-loop filter control information for spatially varying the filtering of the reconstructed version of the decoded picture by the in-loop filter from, for each of the video coding units, a further predetermined parameter set which follows in data stream order the respective video coding unit and which is located within the access unit, AU, of the decoded picture and which comprises spatially selective in-loop filter control information for spatially varying the filtering of the reconstructed version of the decoded picture by the in-loop filter within a portion of the picture which is encoded into the respective video coding unit; and parametrizing the in-loop filter so as to filter the reconstructed version of the decoded picture in a manner depending on the one or more filter coefficients and the spatially selective in-loop filter control information. a decoding core configured to reconstruct a decoded picture from video coding units within an access unit, AU, of a video data stream to obtain a reconstructed version of the decoded picture, wherein the decoding core is configured to start decoding parts of a picture before receiving all parts of the picture; an in-loop filter configured to filter the reconstructed version of the decoded picture to obtain a filtered version of the decoded picture; and a parametrizer configured to parametrize the in-loop filter by: reading one or more filter coefficients for parametrizing the in-loop filter in terms of transfer function from a predetermined parameter set which follows, along data stream order, all of the video coding units and which is located within the access unit, AU, of the decoded picture; reading spatially selective in-loop filter control information for spatially varying the filtering of the reconstructed version of the decoded picture by the in-loop filter from, for each of the video coding units, a further predetermined parameter set which follows in data stream order the respective video coding unit and which is located within the access unit, AU, of the decoded picture and which comprises spatially selective in-loop filter control information for spatially varying the filtering of the reconstructed version of the decoded picture by the in-loop filter within a portion of the picture which is encoded into the respective video coding unit; and parametrizing the in-loop filter so as to filter the reconstructed version of the decoded picture in a manner depending on the one or more filter coefficients and the spatially selective in-loop filter control information. reading one or more filter coefficients for parametrizing the in-loop filter in terms of transfer function from a predetermined parameter set which follows, along data stream order, all of the video coding units and which is located within the access unit, AU, of the decoded picture; reading spatially selective in-loop filter control information for spatially varying the filtering of the reconstructed version of the decoded picture by the in-loop filter from, for each of the video coding units, a further predetermined parameter set which follows in data stream order the respective video coding unit and which is located within the access unit, AU, of the decoded picture and which comprises spatially selective in-loop filter control information for spatially varying the filtering of the reconstructed version of the decoded picture by the in-loop filter within a portion of the picture which is encoded into the respective video coding unit; and parametrizing the in-loop filter so as to filter the reconstructed version of the decoded picture in a manner depending on the one or more filter coefficients and the spatially selective in-loop filter control information.