A method of decoding three-dimensional and/or multi-layer video data using a high-level-syntax only extension of a two-dimensional, single-layer base video coding specification, the method comprising: decoding, in a sequence parameter set, SPS, data structure for a sequence including a current picture, picture order count, POC, values for reference pictures of the sequence, and optionally decoding, in a slice header of a current slice of the current picture, POC values for reference pictures of the current picture; decoding a second-dimension picture identifier for each of the reference pictures, wherein a second-dimension picture identifier and a POC value together identify a reference picture of the three-dimensional and/or multi-layer video data; and decoding, in accordance with the base video coding specification, the current picture comprising: determining a first motion vector of a first block of the current picture and identifying a first reference picture to which the first motion vector refers based at least in part on a first decoded POC value and a first decoded second-dimension picture identifier; determining a second motion vector of a second block of the current picture and identifying a second reference picture to which the second motion vector refers based at least in part on a second decoded POC value and a second decoded second-dimension picture identifier; determining the type of the first and second motion vectors using said first and second decoded POC values and second dimension picture identifiers, wherein different types of motion vectors include long-term temporal motion vectors, short-term temporal motion vectors, and disparity motion vectors; and disabling motion vector prediction between the first motion vector and the second motion vector when the first motion vector refers to a short-term reference picture and the second motion vector refers to a long-term reference picture. decoding, in a sequence parameter set, SPS, data structure for a sequence including a current picture, picture order count, POC, values for reference pictures of the sequence, and optionally decoding, in a slice header of a current slice of the current picture, POC values for reference pictures of the current picture; decoding a second-dimension picture identifier for each of the reference pictures, wherein a second-dimension picture identifier and a POC value together identify a reference picture of the three-dimensional and/or multi-layer video data; and decoding, in accordance with the base video coding specification, the current picture comprising: determining a first motion vector of a first block of the current picture and identifying a first reference picture to which the first motion vector refers based at least in part on a first decoded POC value and a first decoded second-dimension picture identifier; determining a second motion vector of a second block of the current picture and identifying a second reference picture to which the second motion vector refers based at least in part on a second decoded POC value and a second decoded second-dimension picture identifier; determining the type of the first and second motion vectors using said first and second decoded POC values and second dimension picture identifiers, wherein different types of motion vectors include long-term temporal motion vectors, short-term temporal motion vectors, and disparity motion vectors; and disabling motion vector prediction between the first motion vector and the second motion vector when the first motion vector refers to a short-term reference picture and the second motion vector refers to a long-term reference picture. determining a first motion vector of a first block of the current picture and identifying a first reference picture to which the first motion vector refers based at least in part on a first decoded POC value and a first decoded second-dimension picture identifier; determining a second motion vector of a second block of the current picture and identifying a second reference picture to which the second motion vector refers based at least in part on a second decoded POC value and a second decoded second-dimension picture identifier; determining the type of the first and second motion vectors using said first and second decoded POC values and second dimension picture identifiers, wherein different types of motion vectors include long-term temporal motion vectors, short-term temporal motion vectors, and disparity motion vectors; and disabling motion vector prediction between the first motion vector and the second motion vector when the first motion vector refers to a short-term reference picture and the second motion vector refers to a long-term reference picture.