In one example, a device includes a video coder configured to code a picture order count (POC) value for a first picture of video data, code a second-dimension picture identifier for the first picture, and code, in accordance with a base video coding specification or an extension to the base video coding specification, a second picture based at least in part on the POC value and the second-dimension picture identifier of the first picture. The video coder may comprise a video encoder or a video decoder. The second-dimension picture identifier may comprise, for example, a view identifier, a view order index, a layer identifier, or other such identifier. The video coder may code the POC value and the second-dimension picture identifier during coding of a motion vector for a block of the second picture, e.g., during advanced motion vector prediction or merge mode coding.