SMPlayer is a graphical user interface (GUI) for the award-winning
MPlayer, which is capable of playing almost all known video and audio
formats. See a list of all supported formats
SMPlayer is multi-platform and runs on Windows and Linux. It has been developed using the Qt toolkit.
MPlayer is a powerful media player but it's a command-line application and many people find it hard to use. SMPlayer makes easy to access the most common and useful functions of MPlayer, like selecting the audio or subtitle track, enabling video filters, adjusting the audio delay, playback speed and many more, using a nice and intuitive interface. A complete preferences dialog is also available with options to fine-tune performance, change the color and font of subtitles, set key shortcuts...
But SMPlayer also adds other interesting features like the possibility to play Youtube videos, search and download subtitles, create video preview images...
One of the most interesting features of SMPlayer: it remembers the settings of all files you play. So you start to watch a movie but you have to leave... don't worry, when you open that movie again it will resume at the same point you left it, and with the same settings: audio track, subtitles, volume...
Some other interesting features:
SMPlayer also supports MPlayer2. MPlayer2 is a fork of MPlayer which includes new features like support for Matroska's ordered chapters or precise seeks, and also provides some bug fixes. See a detailed list of differences.
Update It seems MPlayer2 is not developed anymore and it has been superseded by mpv. Fortunately SMPlayer now supports mpv as well!
The SMPlayer packages for Windows already include a recent version of MPlayer. But if you're looking for even newer builds of MPlayer or MPlayer2, please take a look at these projects maintained by redxii: