Compressed files may be stored inside a wrapper such as Quicktime (.mov) or MXF. The wrapper holds all the parts together and provides instructions about how to play the content.
Intra-frame compression systems work on individual frames. They provide a lower compression ratio, but are much easier to handle in post.
Inter-frame compression systems work on groups of pictures (GOP’s). They provide a higher compression ratio but will need a lot effort to encode or decode.
Be careful about mixing compression systems. Each has it’s own different way of saving space, so when mixed, these can cause issues by interfering with each other. This is called concatenation.
Workflow is the buzzword in digital television. It is about working out an effective way to use the systems and get a good result which will keep quality high and deliver results in a cost effective way. Getting the compression right is a key part of workflow.