Specifications

However, using combining on files that do not come from a single source is not recommended. In this case

you should use the joiner to ensure proper attention is paid to audio and video alignments.

Note: Combining does minimal error checking on each component file. For example combining different file

types, such as program and transport streams may result in unpredictable results or even program failure.

Joining does not have this limitation as each file is opened and processed independently.