A method for use in encoding and decoding a group of pictures in a video stream for High Efficiency Video Coding, HEVC, comprising: identifying a current picture in the group of pictures for encoding or decoding; identifying a collocated picture in the group of pictures using syntax to determine if a collocated picture index should be accessed to identify the collocated picture, wherein identifying the collocated picture includes: indicating which reference picture in a first collocated picture index list and a second collocated picture index list provides the collocated picture, depending upon a state of a flag; if the flag is in a first state: providing a first reference picture set number that counts all reference pictures in the first collocated picture index list that are prior to a current picture in decoding order, and that may be used in inter prediction of the current picture; and determining if the first reference picture set number is greater than 1, and if so identifying a collocated picture identified using a collocated picture index syntax from a determined reference picture set; if the flag is in a second state: providing a second reference picture set number that counts all reference pictures in the second collocated picture index list that are prior to the current picture in decoding order and that may be used in inter prediction of the current picture, and determining if the second reference picture set number is greater than 1, and if so identifying the collocated picture identified with the collocated picture index syntax from the determined reference picture set; and using the collocated picture to encode or decode the current picture. identifying a current picture in the group of pictures for encoding or decoding; identifying a collocated picture in the group of pictures using syntax to determine if a collocated picture index should be accessed to identify the collocated picture, wherein identifying the collocated picture includes: indicating which reference picture in a first collocated picture index list and a second collocated picture index list provides the collocated picture, depending upon a state of a flag; if the flag is in a first state: providing a first reference picture set number that counts all reference pictures in the first collocated picture index list that are prior to a current picture in decoding order, and that may be used in inter prediction of the current picture; and determining if the first reference picture set number is greater than 1, and if so identifying a collocated picture identified using a collocated picture index syntax from a determined reference picture set; if the flag is in a second state: providing a second reference picture set number that counts all reference pictures in the second collocated picture index list that are prior to the current picture in decoding order and that may be used in inter prediction of the current picture, and determining if the second reference picture set number is greater than 1, and if so identifying the collocated picture identified with the collocated picture index syntax from the determined reference picture set; and using the collocated picture to encode or decode the current picture. indicating which reference picture in a first collocated picture index list and a second collocated picture index list provides the collocated picture, depending upon a state of a flag; if the flag is in a first state: providing a first reference picture set number that counts all reference pictures in the first collocated picture index list that are prior to a current picture in decoding order, and that may be used in inter prediction of the current picture; and determining if the first reference picture set number is greater than 1, and if so identifying a collocated picture identified using a collocated picture index syntax from a determined reference picture set; providing a first reference picture set number that counts all reference pictures in the first collocated picture index list that are prior to a current picture in decoding order, and that may be used in inter prediction of the current picture; and determining if the first reference picture set number is greater than 1, and if so identifying a collocated picture identified using a collocated picture index syntax from a determined reference picture set; if the flag is in a second state: providing a second reference picture set number that counts all reference pictures in the second collocated picture index list that are prior to the current picture in decoding order and that may be used in inter prediction of the current picture, and determining if the second reference picture set number is greater than 1, and if so identifying the collocated picture identified with the collocated picture index syntax from the determined reference picture set; and providing a second reference picture set number that counts all reference pictures in the second collocated picture index list that are prior to the current picture in decoding order and that may be used in inter prediction of the current picture, and determining if the second reference picture set number is greater than 1, and if so identifying the collocated picture identified with the collocated picture index syntax from the determined reference picture set; and using the collocated picture to encode or decode the current picture.