A method of processing a file for storing multi-layer bitstreams of encoded video data, the method comprising: obtaining an operation point reference track in the file, wherein an operation point available for a bitstream in the file is described in the file using an operation point information sample group that is signaled in the operation point reference track; obtaining one or more additional tracks in the file, wherein no operation point information sample group is signaled in any of the additional tracks; for each respective sample of each respective additional track of the one or more additional tracks, determining whether to consider the respective sample as a part of the operation point information sample group, wherein: based on the operation point reference track containing a sample that is temporally collocated, such that the sample is aligned in time with the respective sample in the respective additional track, the respective sample in the respective additional track is considered part of the operation point information sample group, and based on the operation point reference track not containing a sample that is temporally collocated, such there is not a sample which is aligned in time with the respective sample in the respective additional track, the respective sample in the respective additional track is considered part of an operation point information sample group in the temporally collocated position of the respective sample of the respective additional track; and performing a sub-bitstream extraction process that extracts the operation point from the bitstream. obtaining an operation point reference track in the file, wherein an operation point available for a bitstream in the file is described in the file using an operation point information sample group that is signaled in the operation point reference track; obtaining one or more additional tracks in the file, wherein no operation point information sample group is signaled in any of the additional tracks; for each respective sample of each respective additional track of the one or more additional tracks, determining whether to consider the respective sample as a part of the operation point information sample group, wherein: based on the operation point reference track containing a sample that is temporally collocated, such that the sample is aligned in time with the respective sample in the respective additional track, the respective sample in the respective additional track is considered part of the operation point information sample group, and based on the operation point reference track not containing a sample that is temporally collocated, such there is not a sample which is aligned in time with the respective sample in the respective additional track, the respective sample in the respective additional track is considered part of an operation point information sample group in the temporally collocated position of the respective sample of the respective additional track; and based on the operation point reference track containing a sample that is temporally collocated, such that the sample is aligned in time with the respective sample in the respective additional track, the respective sample in the respective additional track is considered part of the operation point information sample group, and based on the operation point reference track not containing a sample that is temporally collocated, such there is not a sample which is aligned in time with the respective sample in the respective additional track, the respective sample in the respective additional track is considered part of an operation point information sample group in the temporally collocated position of the respective sample of the respective additional track; and performing a sub-bitstream extraction process that extracts the operation point from the bitstream.