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Wireless Video Formats and Compression
The best format for transporting video is in its native uncompressed state. Using this format prevents image distortions that arise from compression and eliminates the delays incurred by encoding and decoding the signal. There are a few wireless technologies that can support these bit rates; these can be easily deployed by broadcasters if the system setup rules are properly followed.
The vast majority of wireless transmission systems use compression to reduce the bit rate of standard definition and HD signals enough to fit within the channel capacities of the various wireless frequency bands. In a few cases, this compression is relatively light (meaning that a high bit rate channel is used), but in most cases heavy compression is required to reduce the bit rate so that it will fit within the available channel.
Compression technologies can be divided into two distinct categories: intra-frame and inter-frame. Intra-frame (also called I-frame-only) compression processes each image (frame) of a video sequence separately, with no dependence between adjacent frames. Inter-frame (or motion-compensation-based) compression can achieve higher amounts of compression (i.e. lower resulting bit rates) by only transmitting the differences between adjacent video frames.
In general, I-frame-only compressed streams are easier to edit and offer lower end-to-end delay, with the tradeoff of higher bit rates as compared to inter-frame compression. Technologies such as Motion JPEG, JPEG 2000, and AVCi use intra-frame compression and are commonly found on surveillance cameras that need to provide traceability of every frame of video for possibly use as evidence in the court of law. MPEG2, H.264, HEVC and related technologies that use inter-frame compression are widely used for wireless applications, particularly those that require very low bit rates.
