Mobile video is taking off in Japan, where mobile operator NTT DoCoMo just invested $45.5 million in PacketVideo, which s a long-time supplier of mobile video software. The all-cash investment gives NTT Docomo a 35 percent stake in PacketVideo, which is s subsidiary of NextWave Wireless (a holding company that owns rights to wireless spectrum in the U.S. which it plans to use for a Wimax network). NextWave acquired PacketVideo in 2005 and the company is now its main source of cash.

The investment indicates how important PacketVideo’s technology is to NTT Docomo, and raises the possibility of an outright purchase down the line. Other customers of PacketVideo include Verizon Wireless, Orange (in France), and T-Mobile. They might not feel so warm and fuzzy about PacketVideo now being so closely aligned with another carrier, even if it is in Japan.

In the past, NTT DoCoMo tried to expand abroad through an aggressive investment program. Maybe it sees cheap assets it wants to grab once again. The $45.5 million investment values PacketVideo at $130 million.