03.10.2010 09:31 AM
Originally featured on BroadcastEngineering.com
New HD wireless camera systems deliver near zero-delay transmission in Vancouver
A new license-free wireless technology was employed at the Winter Olympics in Vancouver to deliver uncompressed HD video of the hockey competition from multiple untethered cameras roaming General Motors Place.
Relying on an emerging next-generation WiFi technology known as multi-input and multi-output (MIMO) antenna technology, the system actually turned the concrete structure of the venue and its resulting RF reflections to its advantage to deliver wireless HD signals with about 1ms of delay. By using multiple antennas on the camera transmitter as well as multiple receive antennas and receivers, the system uses multipath reflections to transmit the equivalent of 800Mb/s.
The Meridian system deployed in Vancouver from London-based Boxx TV uses license-free spectrum between 5.1GHz and 5.8GHz. Multiple low-cost receive antennas were located throughout the hockey venue, each of which provided an input to a video switcher. The Meridian system identifies the strongest signal at any given moment coming into the switcher and instructs it to take the strongest to air. In Vancouver, this setup allowed wireless camera operators to follow players and coaches down hallways and into locker rooms without any dropouts.
Unlike traditional COFDM approaches, the system deployed for the hockey coverage did not rely on compression technologies, such as MPEG-4 H.264, to reduce how much data must be transmitted and, thus, the bandwidth required. Meridian employs a technique that examines each frame for the most noticeable pixels to the human eye and protects those during transmission, said company CTO Scott Walker. Those that aren’t as important are the first to be dropped off.
According to Walker, the approach Meridian takes to transmitting HD wirelessly essentially eliminates visual artifacts that typically result from fast panning and zooming. Equally important is a lack of encoding delay.
“Because we are not actually processing and having to compress the picture, the delay is less than 1ms, which is like a few lines. So it’s basically zero delay,” Walker said. As a result, cuts between fixed cameras and wireless cameras can be seamless, something that is particularly important in fast-moving sports coverage.