A video coding mechanism for viewpoint dependent video coding is disclosed. The mechanism includes mapping a spherical video signal, stitched from multiple directional video signals, into a plurality of sub-picture video signals each containing a sequence of sub-pictures. The plurality of sub-picture video signals are encoded as a plurality of sub-picture bitstreams. The plurality of sub-picture bitstreams are composed into a plurality of sub-picture tracks to be compatible with a multi-bitstream merge function for reconstruction of the spherical video signal. A track level mergable indication is encoded within a track level box for the sub-picture tracks, which indicates the sub-picture tracks are compatible with the multi-bitstream merge function for reconstruction of the spherical video signal.