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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
in /var/log/XFree86.0.log
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:
xv X11/Xv
Older 3dfx drivers were known to have problems with XVideo acceleration, it didn't support either YUY2 or YV12, and so. Verify that you have XFree86 version 4.2.0 or greater, it works OK with YV12 and YUY2. Previous versions, including 4.1.0, crashes 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) 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.
However, MPlayer contains a VIDIX driver for most nVidia cards. Currently it is in beta stage, and has some drawbacks. For more information, see nVidia VIDIX section.
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
PREAMBLE. This document tries to explain in some words what DGA is in general and what the DGA video output driver for MPlayer can do (and what it can't).
WHAT IS DGA.
DGA is short for Direct Graphics
Access and is a means for a program to bypass the X server and
directly modifying the framebuffer memory. Technically spoken this happens
by mapping the framebuffer memory into the memory range of your process.
This is allowed by the kernel only if you have superuser privileges. You
can get these either by logging in as root or by setting the SUID bit on the
MPlayer executable (not
recommended).
There are two versions of DGA: DGA1 is used by XFree 3.x.x and DGA2 was introduced with XFree 4.0.1.
DGA1 provides only direct framebuffer access as described above. For switching the resolution of the video signal you have to rely on the XVidMode extension.
DGA2 incorporates the features of XVidMode extension and also allows switching the depth of the display. So you may, although basically running a 32 bit depth X server, switch to a depth of 15 bits and vice versa.
However DGA has some drawbacks. It seems it is somewhat dependent on the graphics chip you use and on the implementation of the X server's video driver that controls this chip. So it does not work on every system...
INSTALLING DGA SUPPORT FOR MPLAYER. First make sure X loads the DGA extension, see in /var/log/XFree86.0.log:
(II) Loading extension XFree86-DGA
See, XFree86 4.0.x or greater is highly recommended! MPlayer's DGA driver is autodetected by ./configure, or you can force it with --enable-dga.
If the driver couldn't switch to a smaller resolution, experiment with options -vm (only with X 3.3.x), -fs, -bpp, -zoom to find a video mode that the movie fits in. There is no converter right now :(
Become root. DGA needs root
access to be able to write directly video memory. If you want to run it as
user, then install MPlayer SUID root:
chown root/usr/local/bin/mplayerchmod 750/usr/local/bin/mplayerchmod +s/usr/local/bin/mplayer
Now it works as a simple user, too.
This is a big security risk! Never do this on a server or on a computer that can be accessed by other people because they can gain root privileges through SUID root MPlayer.
Now use -vo dga option, and there you go! (hope so:) You should also try if the -vo sdl:driver=dga option works for you! It's much faster!
RESOLUTION SWITCHING. The DGA driver allows for switching the resolution of the output signal. This avoids the need for doing (slow) software scaling and at the same time provides a fullscreen image. Ideally it would switch to the exact resolution (except for honoring aspect ratio) of the video data, but the X server only allows switching to resolutions predefined in /etc/X11/XF86Config (/etc/X11/XF86Config-4 for XFree 4.X.X respectively). Those are defined by so-called modelines and depend on the capabilities of your video hardware. The X server scans this config file on startup and disables the modelines not suitable for your hardware. You can find out which modes survive with the X11 log file. It can be found at: /var/log/XFree86.0.log.
These entries are known to work fine with a Riva128 chip, using the nv.o X server driver module.
Section "Modes" Identifier "Modes[0]" Modeline "800x600" 40 800 840 968 1056 600 601 605 628 Modeline "712x600" 35.0 712 740 850 900 400 410 412 425 Modeline "640x480" 25.175 640 664 760 800 480 491 493 525 Modeline "400x300" 20 400 416 480 528 300 301 303 314 Doublescan Modeline "352x288" 25.10 352 368 416 432 288 296 290 310 Modeline "352x240" 15.750 352 368 416 432 240 244 246 262 Doublescan Modeline "320x240" 12.588 320 336 384 400 240 245 246 262 Doublescan EndSection
DGA & MPLAYER. DGA is used in two places with MPlayer: The SDL driver can be made to make use of it (-vo sdl:driver=dga) and within the DGA driver (-vo dga). The above said is true for both; in the following sections I'll explain how the DGA driver for MPlayer works.
FEATURES. The DGA driver is invoked by specifying -vo dga at the command line. The default behavior is to switch to a resolution matching the original resolution of the video as close as possible. It deliberately ignores the -vm and -fs options (enabling of video mode switching and fullscreen) - it always tries to cover as much area of your screen as possible by switching the video mode, thus refraining from using additional cycles of your CPU to scale the image. If you don't like the mode it chooses you may force it to choose the mode matching closest the resolution you specify by -x and -y. By providing the -v option, the DGA driver will print, among a lot of other things, a list of all resolutions supported by your current XF86Config file. Having DGA2 you may also force it to use a certain depth by using the -bpp option. Valid depths are 15, 16, 24 and 32. It depends on your hardware whether these depths are natively supported or if a (possibly slow) conversion has to be done.
If you should be lucky enough to have enough offscreen memory left to put a whole image there, the DGA driver will use double buffering, which results in much smoother movie playback. It will tell you whether double buffering is enabled or not.
Double buffering means that the next frame of your video is being drawn in some offscreen memory while the current frame is being displayed. When the next frame is ready, the graphics chip is just told the location in memory of the new frame and simply fetches the data to be displayed from there. In the meantime the other buffer in memory will be filled again with new video data.
Double buffering may be switched on by using the option -double and may be disabled with -nodouble. Current default option is to disable double buffering. When using the DGA driver, onscreen display (OSD) only works with double buffering enabled. However, enabling double buffering may result in a big speed penalty (on my K6-II+ 525 it used an additional 20% of CPU time!) depending on the implementation of DGA for your hardware.
SPEED ISSUES. Generally spoken, DGA framebuffer access should be at least as fast as using the X11 driver with the additional benefit of getting a fullscreen image. The percentage speed values printed by MPlayer have to be interpreted with some care, as for example, with the X11 driver they do not include the time used by the X server needed for the actual drawing. Hook a terminal to a serial line of your box and start top to see what is really going on in your box.
Generally spoken, the speedup done by using DGA against 'normal' use of X11 highly depends on your graphics card and how well the X server module for it is optimized.
If you have a slow system, better use 15 or 16 bit depth since they require only half the memory bandwidth of a 32 bit display.
Using a depth of 24 bit is even a good idea if your card natively just supports 32 bit depth since it transfers 25% less data compared to the 32/32 mode.
I've seen some AVI files be played back on a Pentium MMX 266. AMD K6-2 CPUs might work at 400 MHZ and above.
KNOWN BUGS. Well, according to some developers of XFree, DGA is quite a beast. They tell you better not to use it. Its implementation is not always flawless with every chipset driver for XFree out there.
SDL (Simple Directmedia Layer) is basically a unified
video/audio interface. Programs that use it know only about SDL, and not
about what video or audio driver does SDL actually use. For example a Doom
port using SDL can run on svgalib, aalib, X, fbdev, and others, you only
have to specify the (for example) video driver to use with the
SDL_VIDEODRIVER environment variable. Well, in theory.
With MPlayer, we used its X11 driver's software scaler ability for cards/drivers that doesn't support XVideo, until we made our own (faster, nicer) software scaler. Also we used its aalib output, but now we have ours which is more comfortable. Its DGA mode was better than ours, until recently. Get it now? :)
It also helps with some buggy drivers/cards if the video is jerky (not slow system problem), or audio is lagging.
SDL video output supports displaying subtitles under the movie, on the (if present) black bar.
INSTALLATION. You'll have to install svgalib and its development package in order for MPlayer build its SVGAlib driver (autodetected, but can be forced), and don't forget to edit /etc/vga/libvga.config to suit your card and monitor.
Be sure not to use the -fs switch, since it toggles the usage of the software scaler, and it's slow. If you really need it, use the -sws 4 option which will produce bad quality, but is somewhat faster.
EGA (4BPP) SUPPORT. SVGAlib incorporates EGAlib, and MPlayer has the possibility to display any movie in 16 colors, thus usable in the following sets:
The bpp (bits per pixel) value must be set to 4 by hand: -bpp 4
The movie probably must be scaled down to fit in EGA mode:
-vf scale=640:350
or
-vf scale=320:200
For that we need fast but bad quality scaling routine:
-sws 4
Maybe automatic aspect correction has to be shut off:
-noaspect
According to my experience the best image quality on EGA screens can be achieved by decreasing the brightness a bit: -vf eq=-20:0. I also needed to lower the audio samplerate on my box, because the sound was broken on 44kHz: -srate 22050.
You can turn on OSD and subtitles only with the expand filter, see the man page for exact parameters.
Whether to build the FBdev target is autodetected during ./configure. Read the framebuffer documentation in the kernel sources (Documentation/fb/*) for more information.
If your card doesn't support VBE 2.0 standard (older ISA/PCI cards, such as S3 Trio64), only VBE 1.2 (or older?): Well, VESAfb is still available, but you'll have to load SciTech Display Doctor (formerly UniVBE) before booting Linux. Use a DOS boot disk or whatever. And don't forget to register your UniVBE ;))
The FBdev output takes some additional parameters above the others:
If you want to change to a specific mode, then use
mplayer -vm -fbmodename_of_modefilename
-vm alone will choose the most suitable mode from /etc/fb.modes. Can be used together with -x and -y options too. The -flip option is supported only if the movie's pixel format matches the video mode's pixel format. Pay attention to the bpp value, fbdev driver tries to use the current, or if you specify the -bpp option, then that.
-zoom option isn't supported (use -vf scale). You can't use 8bpp (or less) modes.
You possibly want to turn the cursor off:
echo -e '\033[?25l'
or
setterm -cursor off
and the screen saver:
setterm -blank 0
To turn the cursor back on:
echo -e '\033[?25h'
or
setterm -cursor on
FBdev video mode changing does not work with the VESA framebuffer, and don't ask for it, since it's not an MPlayer limitation.
This section is about the Matrox G200/G400/G450/G550 BES (Back-End Scaler)
support, the mga_vid kernel driver.
It has hardware VSYNC support with triple buffering. It works on both
framebuffer console and under X.
This is Linux only! On non-Linux (tested on FreeBSD) systems, you can use VIDIX instead!
Installation:
To use it, you first have to compile mga_vid.o:
cd drivers make
Then create /dev/mga_vid device:
mknod /dev/mga_vid c 178 0
and load the driver with
insmod mga_vid.o
You should verify the memory size detection using the dmesg command. If it's bad, use the mga_ram_size option (rmmod mga_vid first), specify card's memory size in MB:
insmod mga_vid.o mga_ram_size=16
To make it load/unload automatically when needed, first insert the following line at the end of /etc/modules.conf:
alias char-major-178 mga_vid
Then copy the mga_vid.o module to the appropriate
place under /lib/modules/kernel
version/somewhere.
Then run
depmod -a
Now you have to (re)compile MPlayer, ./configure will detect /dev/mga_vid and build the 'mga' driver. Using it from MPlayer goes by -vo mga if you have matroxfb console, or -vo xmga under XFree86 3.x.x or 4.x.x.
The mga_vid driver cooperates with Xv.
The /dev/mga_vid device file can be read for some info, for example by
cat /dev/mga_vid
and can be written for brightness change:
echo "brightness=120" > /dev/mga_vid
This driver uses the kernel's tdfx framebuffer driver to play movies with YUV acceleration. You'll need a kernel with tdfxfb support, and recompile with
./configure --enable-tdfxfb
MPlayer supports displaying movies using OpenGL, but if your platform/driver supports xv as should be the case on a PC with Linux, use xv instead, OpenGL performance is considerably worse. If you have an X11 implementation without xv support, OpenGL is a viable alternative.
Unfortunately not all drivers support this feature. The Utah-GLX drivers (for XFree86 3.3.6) support it for all cards. See http://utah-glx.sf.net for details about how to install it.
XFree86(DRI) 4.0.3 or later supports OpenGL with Matrox and Radeon cards, 4.2.0 or later supports Rage128. See http://dri.sf.net for download and installation instructions.
A hint from one of our users: the GL video output can be used to get vsynced TV output. You'll have to set an environment variable (at least on nVidia):
export $__GL_SYNC_TO_VBLANK=1
AAlib is a library for displaying graphics in text mode, using powerful ASCII renderer. There are lots of programs already supporting it, like Doom, Quake, etc. MPlayer contains a very usable driver for it. If ./configure detects aalib installed, the aalib libvo driver will be built.
You can use some keys in the AA Window to change rendering options:
| Key | Action |
|---|---|
| 1 | decrease contrast |
| 2 | increase contrast |
| 3 | decrease brightness |
| 4 | increase brightness |
| 5 | switch fast rendering on/off |
| 6 | set dithering mode (none, error distribution, Floyd Steinberg) |
| 7 | invert image |
| 8 | toggles between aa and MPlayer control |
The following command line options can be used:
Vchange OSD color
VChange subtitle color
where V can be:
0 (normal),
1 (dark),
2 (bold),
3 (bold font),
4 (reverse),
5 (special).
AAlib itself provides a large sum of options. Here are some important:
The rendering is very CPU intensive, especially when using AA-on-X (using aalib on X), and it's least CPU intensive on standard, non-framebuffer console. Use SVGATextMode to set up a big textmode, then enjoy! (secondary head Hercules cards rock :)) (but IMHO you can use -vf 1bpp option to get graphics on hgafb:)
Use the -framedrop option if your computer isn't fast enough to render all frames!
Playing on terminal you'll get better speed and quality using the Linux
driver, not curses (-aadriver linux). But therefore you
need write access on
/dev/vcsa<terminal>!
That isn't autodetected by aalib, but vo_aa tries to find the best mode.
See http://aa-project.sf.net/tune for further
tuning issues.
The libcaca
library is a graphics library that outputs text instead of pixels, so that it
can work on older video cards or text terminals. It is not unlike the famous
AAlib library.
libcaca needs a terminal to work, thus
it should work on all Unix systems (including Mac OS X) using either the
slang library or the
ncurses library, on DOS using the
conio.h library, and on Windows systems
using either slang or
ncurses (through Cygwin emulation) or
conio.h. If
./configure
detects libcaca, the caca libvo driver
will be built.
The differences with AAlib are
the following:
But libcaca also has the
following limitations:
You can use some keys in the caca window to change rendering options:
| Key | Action |
|---|---|
| d |
Toggle libcaca dithering methods.
|
| a |
Toggle libcaca antialiasing.
|
| b |
Toggle libcaca background.
|
libcaca will also look for certain environment variables:
Use the -framedrop option if your computer is not fast enough to render all frames.
This driver was designed and introduced as a generic driver for any video card which has VESA VBE 2.0 compatible BIOS. Another advantage of this driver is that it tries to force TV output on. VESA BIOS EXTENSION (VBE) Version 3.0 Date: September 16, 1998 (Page 70) says:
Dual-Controller Designs. VBE 3.0 supports the dual-controller design by assuming that since both controllers are typically provided by the same OEM, under control of a single BIOS ROM on the same graphics card, it is possible to hide the fact that two controllers are indeed present from the application. This has the limitation of preventing simultaneous use of the independent controllers, but allows applications released before VBE 3.0 to operate normally. The VBE Function 00h (Return Controller Information) returns the combined information of both controllers, including the combined list of available modes. When the application selects a mode, the appropriate controller is activated. Each of the remaining VBE functions then operates on the active controller.
So you have chances to get working TV-out by using this driver. (I guess that TV-out frequently is standalone head or standalone output at least.)
ADVANTAGES
int 10h handler thus it's not
an emulator - it calls real things of
real BIOS in real-mode
(actually in vm86 mode).
DISADVANTAGES
root.
Don't use this driver with GCC 2.96! It won't work!
COMMAND LINE OPTIONS AVAILABLE FOR VESA
optsdga to force dga mode and
nodga to disable dga mode. In dga mode you can enable
double buffering via the -double option. Note: you may omit
these parameters to enable autodetection of
dga mode.
KNOWN PROBLEMS AND WORKAROUNDS
Avoid if possible. Outputs to X11 (uses shared memory extension), with no hardware acceleration at all. Supports (MMX/3DNow/SSE accelerated, but still slow) software scaling, use the options -fs -zoom. Most cards have hardware scaling support, use the -vo xv output for them, or -vo xmga for Matrox cards.
The problem is that most cards' driver doesn't support hardware acceleration on the second head/TV. In those cases, you see green/blue colored window instead of the movie. This is where this driver comes in handy, but you need powerful CPU to use software scaling. Don't use the SDL driver's software output+scaler, it has worse image quality!
Software scaling is very slow, you better try changing video modes instead. It's very simple. See the DGA section's modelines, and insert them into your XF86Config.
If you can't find the modes you inserted, browse XFree86's output. Some drivers can't use low pixelclocks that are needed for low resolution video modes.
PREAMBLE. VIDIX is the abbreviation for VIDeo Interface for *niX. VIDIX was designed and introduced as an interface for fast user-space drivers providing such video performance as mga_vid does for Matrox cards. It's also very portable.
This interface was designed as an attempt to fit existing video acceleration interfaces (known as mga_vid, rage128_vid, radeon_vid, pm3_vid) into a fixed scheme. It provides a high level interface to chips which are known as BES (BackEnd scalers) or OV (Video Overlays). It doesn't provide low level interface to things which are known as graphics servers. (I don't want to compete with X11 team in graphics mode switching). I.e. main goal of this interface is to maximize the speed of video playback.
USAGE
Indeed it doesn't matter which video output driver is used with VIDIX.
REQUIREMENTS
USAGE METHODS. When VIDIX is used as subdevice (-vo vesa:vidix) then video mode configuration is performed by video output device (vo_server in short). Therefore you can pass into command line of MPlayer the same keys as for vo_server. In addition it understands -double key as globally visible parameter. (I recommend using this key with VIDIX at least for ATI's card). As for -vo xvidix, currently it recognizes the following options: -fs -zoom -x -y -double.
Also you can specify VIDIX's driver directly as third subargument in command line:
mplayer -vo xvidix:mga_vid.so -fs -zoom -double file.avior
mplayer -vo vesa:vidix:radeon_vid.so -fs -zoom -double -bpp 32 file.aviBut it's dangerous, and you shouldn't do that. In this case given driver will be forced and result is unpredictable (it may freeze your computer). You should do that ONLY if you are absolutely sure it will work, and MPlayer doesn't do it automatically. Please tell about it to the developers. The right way is to use VIDIX without arguments to enable driver autodetection.
Since VIDIX requires direct hardware access you can either run it as root or set the SUID bit on the MPlayer binary (Warning: This is a security risk!). Alternatively, you can use a special kernel module, like this:
Download the development version of svgalib (for example 1.9.17), OR download a version made by Alex especially for usage with MPlayer (it doesn't need the svgalib source to compile) from here.
Compile the module in the svgalib_helper directory (it can be found inside the svgalib-1.9.17/kernel/ directory if you've downloaded the source from the svgalib site) and insmod it.
To create the necessary devices in the /dev directory, do a
make device
in the svgalib_helper dir, as root.
Move the svgalib_helper directory to mplayer/main/libdha/svgalib_helper.
Required if you download the source from the svgalib site: Remove the comment before the CFLAGS line containing "svgalib_helper" string from the libdha/Makefile.
Recompile and install libdha.
Currently most ATI cards are supported natively, from Mach64 to the newest Radeons.
There are two compiled binaries: radeon_vid for Radeon and rage128_vid for Rage 128 cards. You may force one or let the VIDIX system autoprobe all available drivers.
Matrox G200, G400, G450 and G550 have been reported to work.
The driver supports video equalizers and should be nearly as fast as the Matrox framebuffer
There is a driver available for the Trident Cyberblade/i1 chipset, which can be found on VIA Epia motherboards.
The driver was written and is maintained by Alastair M. Robinson
Although there is a driver for the 3DLabs GLINT R3 and Permedia3 chips, no one has tested it, so reports are welcome.
An unique feature of the nvidia_vid driver is its ability to display video on plain, pure, text-only console - with no framebuffer or X magic whatsoever. For this purpose, we'll have to use the cvidix video output, as the following example shows:
mplayer -vo cvidix example.avi
"DirectFB is a graphics library which was designed with embedded systems in mind. It offers maximum hardware accelerated performance at a minimum of resource usage and overhead." - quoted from http://www.directfb.org
I'll exclude DirectFB features from this section.
Though MPlayer is not supported as a "video provider" in DirectFB, this output driver will enable video playback through DirectFB. It will - of course - be accelerated, on my Matrox G400 DirectFB's speed was the same as XVideo.
Always try to use the newest version of DirectFB. You can use DirectFB options on the command line, using the -dfbopts option. Layer selection can be done by the subdevice method, e.g.: -vo directfb:2 (layer -1 is default: autodetect)
Please read the main DirectFB section for general information.
This video output driver will enable CRTC2 (on the second head) on Matrox G400/G450/G550 cards, displaying video independent of the first head.
Ville Syrjala's has a README and a HOWTO on his homepage that explain how to make DirectFB TV output run on Matrox cards.