This. Some files have to be converted (which I assume the OP understands this and was just trying to understand which ones it would convert), but the speed at which these files convert is based on a number of variables. The same video in two different video formats could takes vastly different amounts of time to convert because some wrappers convert to others better.
Originally Posted by TheWeeBear
Once the file is converted, then it should transfer at a rate of 20mb - 50mp a second, again depending on a number of factors.