Usage:

1. FGS
decoder base_layer_bitstream_file fgsbitstream_file output_file width height

2. FGST
decoder base_layer_bitstream_file enhn_layer_bitstream_file output_file width height

3. FGS + FGST
decoder base_layer_bitstream_file fgsbitstream_file enhn_layer_bitstream_file output_file width height
