Ironically, the default GUI of MPLayer (for both GNU/Linux and MS Windows) is a joke (no disrespect intended for the developers :D). It doesn't even resembles a fraction of the true power/features of the MPLayer command-line version. Because of this reason, developers all around the world has created GUI front-ends that uses the original mplayer command-line as the "engine", according to this official "related projects" page at MPlayer's web site, you'll find a hell lot of it :).
Anyhow, in the past I've used several of those GUI under both GNU/Linux and MS Windows. But SMPlayer and KMplayer are the ones that I like the most (if you know even better ones... please share! :D). Recently I came across a new front-end that uses the Mplayer called, MPlayerWW and I gotta say even after using it for a very short period... it really impressed me.
This MPlayer WW does carry around MPlayer characteristics such as fast loading times and decodes multimedia files quite efficiently (meaning low CPU usage while playing, without loosing the quality of course) and the GUI is beautifully designed that stays really simple (skin-able) yet it gives a huge list of additional features that can be really useful in times too.
|Even the OpenGL rendering worked really well with my old ATI card ...|
*. MPlayer uses the ffmpeg library (including many others) thus can decode almost all the known multimedia formats: MPEG 1/2/4, H.264/263, Xvid, Divx, AAC, MP3, Theora, OGG Vorbis, Flac, OGM, Blu-Ray, etc.
*. Open DVD/CD or even HD TV via the main menu.
*. Supports both Direct 3D (without breaking the Window Aero interface, etc) and OpenGL rendering outputs.
*. Manually assign shortcut keys.
*. Built in Playlist (not the most subtly embedded one ... my only complain).
*. Change video settings such as: Hue, Brightness or Contract with built in GUI tools.
*. Enable/Disable file association.
*. Change subtitle fonts, adjust delays, optimized DVD subs or download ones online, etc.
*. Gain/Boost audio levels.
*. Change audio/video delays (another highly useful feature for a this kind of application, no more voices before talking :P).
*. Add several (both audio and video related) filters for enhancing such as: Denoise, Deinterlace, DSP effects, re-sampling, rotate, scaling, etc.
*. Comes with MediaInfo built into it, so you can get advanced media info such as: bitrate, resolution, author, encoding library, etc.
These are just a fraction of the features that you can access via its "Preferences" section. Nothing is perfect, so I shouldn't brag that much :/ ... but I have a WMV file (WM formats in general are usually resource "hogs" and are not optimized codes in my experience) that takes a lot of my CPU cycles of my old Laptop.
I played with MPlayer-WW and not only it decoded the file, but it did it noticeably lesser amount of CPU usage thanks the internal optimized codec library (I think) and it was impressive. Other things such as the progress-bar "sensitivity" is really good too. As mentioned above, it supports Skins (comes with few of its own) thus you can easily change the look-n-feel.
|And when you're bored with it... just change the "skin" ;-)...|
So, if you're searching for one of the best GUIs for the open-source, free MPLayer multimedia rendering engine which doesn't need any third-party codec and plays almost all the known popular formats + can also be used as a portable application, then I humbly advice you to give a try at it!.
Get it from this MPlayer-WW home page. Enjoy!.