Under XFree86 4.0.2 or newer, you can use your card's hardware YUV routines using the XVideo extension. This is what the option -vo xv uses. Also, this driver supports adjusting brightness/contrast/hue/etc. (unless you use the old, slow DirectShow DivX codec, which supports it everywhere), see the man page.
In order to make this work, be sure to check the following:
You have to use XFree86 4.0.2 or newer (former versions don't have XVideo)
Your card actually supports hardware acceleration (modern cards do)
X loads the XVideo extension, it's something like this:
(II) Loading extension XVideo
This loads only the XFree86's extension. In a good install, this is always loaded, and doesn't mean that the card's XVideo support is loaded!
Your card has Xv support under Linux. To check, try xvinfo, it is the part of the XFree86 distribution. It should display a long text, similar to this:
X-Video Extension version 2.2 screen #0 Adaptor #0: "Savage Streams Engine" number of ports: 1 port base: 43 operations supported: PutImage supported visuals: depth 16, visualID 0x22 depth 16, visualID 0x23 number of attributes: 5 (...) Number of image formats: 7 id: 0x32595559 (YUY2) guid: 59555932-0000-0010-8000-00aa00389b71 bits per pixel: 16 number of planes: 1 type: YUV (packed) id: 0x32315659 (YV12) guid: 59563132-0000-0010-8000-00aa00389b71 bits per pixel: 12 number of planes: 3 type: YUV (planar) (...etc...)
It must support YUY2 packed, and YV12 planar pixel formats to be usable with MPlayer.
And finally, check if MPlayer was compiled with 'xv' support. Do a mplayer -vo help | grep xv . If 'xv' support was built a line similar to this should appear:
Older 3dfx drivers were known to have problems with XVideo acceleration, it didn't support YUY2 or YV12 colorspaces. Verify that you have XFree86 version 4.2.0 or later, it can handle YV12 and YUY2 while previous versions, including 4.1.0, crash with YV12. If you experience strange effects using -vo xv, try SDL (it has XVideo, too) and see if it helps. Check the SDL section for details.
OR, try the NEW -vo tdfxfb driver! See the tdfxfb section.
S3 Savage3D's should work fine, but for Savage4, use XFree86 version 4.0.3 or greater (in case of image problems, try 16bpp). As for S3 Virge: there is xv support, but the card itself is very slow, so you better sell it.
There is now a native framebuffer driver for S3 Virge cards similiar to tdfxfb. Set up your framebuffer (e.g. append "vga=792 video=vesa:mtrr" to your kernel comand line) and use -vo s3fb (-vf yuy2 and -dr will also help).
It's currently unclear which Savage models lack YV12 support, and convert by driver (slow). If you suspect your card, get a newer driver, or ask politely on the MPlayer-users mailing list for an MMX/3DNow! enabled driver.
nVidia isn't always a very good choice under Linux ... XFree86's open-source driver supports most of these cards, but for some cases, you'll have to use the binary closed-source nVidia driver, available at nVidia's web site. You'll always need this driver if you want 3D acceleration, too.
Riva128 cards don't have XVideo support with XFree86's nVidia driver :( Complain to nVidia.
The GATOS driver (which you should use, unless you have Rage128 or Radeon) has VSYNC enabled by default. It means that decoding speed (!) is synced to the monitor's refresh rate. If playing seems to be slow, try disabling VSYNC somehow, or set refresh rate to a n*(fps of the movie) Hz.
Radeon VE - if you need X, use XFree86 4.2.0 or greater for this card. No TV out support. Of course with MPlayer you can happily get accelerated display, with or without TV output, and no libraries or X are needed. Read the VIDIX section.
These cards can be found in many laptops. You must use XFree86 4.3.0 or above, or else use Stefan Seyfried's Xv-capable drivers. Just choose the one that applies to your version of XFree86.
XFree86 4.3.0 includes Xv support, yet Bohdan Horst sent a small patch against the XFree86 sources that speeds up framebuffer operations (so XVideo) up to four times. The patch has been included in XFree86 CVS and should be in the next release after 4.3.0.
To allow playback of DVD sized content change your XF86Config like this:
Section "Device" [...] Driver "neomagic" Option "OverlayMem" "829440" [...] EndSection
If you want to use Xv with a Trident card, provided that it doesn't work with 4.1.0, install XFree 4.2.0. 4.2.0 adds support for fullscreen Xv support with the Cyberblade XP card.
Alternatively, MPlayer contains a VIDIX driver for the Cyberblade/i1 card.
If you want to use Xv with a Kyro based card (for example Hercules Prophet 4000XT), you should download the drivers from the PowerVR site.
These cards can be found in many laptops. Recent Xorg is recommended.
To allow playback of DVD sized (and larger) content change your XF86Config/xorg.conf like this:
Section "Device" [...] Driver "intel" Option "LinearAlloc" "6144" [...] EndSection
Lack of this option usually results in an error like
X11 error: BadAlloc (insufficient resources for operation)
when attempting to use -vo xv.