I have some videos from a few years ago,with various formats, such as avi, mpg, wmv, rm, rmvb, .... Their sizes are huge(more than 500 MB, and sometimes > 1GB).

1. Given there may likely be some advance in data compression, I would like to know which file formats and compression methods are recommended these days, by the standard that without losing obvious data, while achieving big size reduction.
2. How can I perform the file format conversion and data compression in Ubuntu 12.04? Command line and batch ways would be the most convenient, although GUI ways are also appreciated.

Thanks and regards!