NHK Develops HDTV Broadcast Camera Using Milliwaves
Japan Broadcasting Corp (NHK) developed a wireless broadcast camera that can transmit HDTV images with little delay by using milliwaves.
The delay per frame is less than 33ms, according to the company. Because transmission capacity was increased due to the use of the millimeter waveband, it became possible to use a low-delay video compression/expansion system.
The new camera will eliminate problems such as the lag between image and sound that occurs in close-up shots of a performer's mouth and the discomfort felt by the audience at the time of switching from or to a low-delay wired camera, according to NHK.
In existing wireless cameras, which use the microwave band, there is a transmission delay of about 0.5 seconds. Thus, when a wireless camera and a wired camera are used together, video production is restricted to some extent due to the difference in delay time between the cameras.
However, milliwaves tend to move in a straight line and are weakened by obstacles, making it difficult to stably transmit signals. This time, NHK applied diversity combining to radio waves received by four receivers and succeeded in shooting images without an interruption while freely moving around.
The broadcast camera features a data transmission speed of 80.3Mbps and an MPEG-2 video encoding system. The transmission frequency is 42GHz band (41.0 to 42.0GHz), while the channel spacing is 62.5MHz. The occupied bandwidth is 54.4MHz, and the transmission output is 100mW.
NHK used the camera for the 59th NHK Kohaku Utagassen music show, which was broadcast at the end of 2008, for the first time.