A method of processing video data, the method comprising: receiving a file having a format for HEVC content encoded with multiple temporal sub-layers, wherein each temporal sub-layer is associated with a different temporal identifier, wherein: the file contains samples, each of the samples contains a respective coded picture of the video data, each of the samples being associated with a temporal identifier indicative of the temporal sub-layer to which the sample belongs, the file includes a box that identifies a sample group, wherein the box does not include the samples, and wherein the box includes an entry that marks which ones of the samples are step-wise temporal sub-layer access, STSA, samples, being samples that do not use samples prior to the STSA sample in decoding order with the same temporal identifier as the STSA sample for inter prediction reference, and enable up-switching to a temporal sub-layer containing the respective STSA sample by prediction of the STSA sample and/or subsequent samples in the temporal sub-layer containing the respective STSA sample using samples prior to the STSA sample from an immediately lower temporal sub-layer; identifying, based on the entry, STSA samples from among the samples in the file; and, performing up-switching at one of the STSA samples in the sample group. receiving a file having a format for HEVC content encoded with multiple temporal sub-layers, wherein each temporal sub-layer is associated with a different temporal identifier, wherein: the file contains samples, each of the samples contains a respective coded picture of the video data, each of the samples being associated with a temporal identifier indicative of the temporal sub-layer to which the sample belongs, the file includes a box that identifies a sample group, wherein the box does not include the samples, and wherein the box includes an entry that marks which ones of the samples are step-wise temporal sub-layer access, STSA, samples, being samples that do not use samples prior to the STSA sample in decoding order with the same temporal identifier as the STSA sample for inter prediction reference, and enable up-switching to a temporal sub-layer containing the respective STSA sample by prediction of the STSA sample and/or subsequent samples in the temporal sub-layer containing the respective STSA sample using samples prior to the STSA sample from an immediately lower temporal sub-layer; identifying, based on the entry, STSA samples from among the samples in the file; and, the file contains samples, each of the samples contains a respective coded picture of the video data, each of the samples being associated with a temporal identifier indicative of the temporal sub-layer to which the sample belongs, the file includes a box that identifies a sample group, wherein the box does not include the samples, and wherein the box includes an entry that marks which ones of the samples are step-wise temporal sub-layer access, STSA, samples, being samples that do not use samples prior to the STSA sample in decoding order with the same temporal identifier as the STSA sample for inter prediction reference, and enable up-switching to a temporal sub-layer containing the respective STSA sample by prediction of the STSA sample and/or subsequent samples in the temporal sub-layer containing the respective STSA sample using samples prior to the STSA sample from an immediately lower temporal sub-layer; identifying, based on the entry, STSA samples from among the samples in the file; and, performing up-switching at one of the STSA samples in the sample group.