A method of processing video data comprises obtaining a bitstream and locating intra random access pictures (IRAP) or Gradual Decoder Refresh (GDR) pictures among the encoded pictures in the bitstream. Locating the IRAP or GDR pictures may comprise obtaining, from a picture header Network Abstraction Layer (NAL) unit in the bitstream, a syntax element that indicates that a picture associated with the picture header NAL unit must be either an Intra Random Access Picture (IRAP) or a Gradual Decoder Refresh (GDR) picture. The picture header NAL unit contains syntax elements that apply to all slices of the picture associated with the picture header NAL unit.