XnView Software

UMPlayer

UMPlayer plays everything!
UMPlayer is the media player that fills all your needs. With dozens of advanced features and built-in codecs it can handle any media format, and can play Audio CDs, DVDs, (S)VCDs, TV / Radio cards, YouTube™ and SHOUTcast™ streams and even incomplete or damaged media files.

Cross-platform
UMPlayer is written under the Qt platform and is available for Microsoft Windows, Apple Mac OS/X, and GNU/Linux opertaing systems.



Built-in Codecs
With over 270 built-in Audio and Video codecs UMPlayer can handle nearly all media formats, including AAC, AC3, ASF, AVI, DIVX, FLV, H.263, Matroska, MOV, MP3, MP4, MPEG, OGG, QT, RealMedia, VOB, Vorbis, WAV, WMA, WMV, XVID and many more.

SourceForge.net: UMPlayer: This is an SMPlayer fork, obviously

http://www.umplayer.com/
http://sourceforge.net/projects/umplayer

I stumbled onto umplayer a while back. For the most part it's like many other mplayer frontends (particularly smplayer). It is one of the better such programs though. The youtube playing is pretty nice, though 2 weaknesses with it are that it can't play playlists & you can't paste youtube links into it (to play youtube vids in it, you use it's youtube search function to find the video, then click the resulting link).

SMPlayer v.7.0 has just been released and introduces youtube support via pasting link into URL dialog.

I see this new smplayer doesn't support youtube playlists. However, it does support youtube links in conventional playlists (m3u, pls, etc).

Also, if you open the playlist editor via options->playlist, you can drag/drop youtube links directly to it.

marsh wrote:SMPlayer v.7.0 has just been released and introduces youtube support via pasting link into URL dialog.

Not to forget support for mplayer2 too

It looks like that fork knifed mencoder from its features. I haven't seen a difference in playback between mplayers so far.

Mplayer2 is a bit more responsive when skipping around, regular mplayer goes to black screen for an eternity while seeking to the new position.

SMplayer 7.1 now has the standard panel listing youtube search results!

---Edit (Apr. 1, 2012)---
It uses a component called smtube. It can now use other players including mplayer & vlc.