Flight test imagery - Getting more for less
V.D. Vaughn, Robert A. Lindsay · 1988
Transmission of television quality live digital imagery requires nearly 60 Mbs when using Pulse Code Modulation (PCM). Many methods of compression of imagery have been investigated. Simple techniques, such as Differential Pulse Code Modulation (DPCM), are relatively easy to implement but have limited performance. Transform techniques, such as Discrete Cosine Transform (DCT), offer more compression but are difficult to implement at video rates within stringent airborne hardware constraints. Vector Quantization has been an area of research for many years. Advances in digital hardware during the last few years have made many implementations possible, therefore spurring renewed interest in active research. Vector Quantization has been applied to various types of data and results of the experimentation have been appearing regularly in the literature during the past several years. This technique of image coding has applications for any digitally sampled waveform. images are taken every 1130th of a second. The other types of sensors are for special purpose image collection and are not used for real time monitoring of remote activity as in flight test environments. Analog imagery, such as a television signal, requires 5MHz of analog channel bandwidth. The same signal when digitized using Pulse Code Modulation (PCM) requires 60 to 80 Mbits per second (Mbps) of a digital communication channel. If PCM were used as the final digital signal, the result is an expansion of bandwidth to convert from an analog to a digital imagery system. The amount of expansion would depend on the type of modulation. Data compression techniques reduce the bit rate of the PCM digital signal. This paper will address issues surrounding digital video imagery and show how frame rate, spatial resolution, sample resolution, and data compression techniques effect the bit rates while providing television quality imagery at 1 to 15 Mbps.