Difference between revisions of "XvMC"

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(HDTV w/o XvMC on AMD 64 X2 6000+)
(Added bob deinterlacer info)
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=== OSD Flicker ===
=== OSD Flicker ===
If you are using MythTV version 0.18 and you experience severe OSD stutter or flicker when XvMC is enabled, try upgrading to 0.19. The OSD flicker is fixed for the author in 0.19 with an Nvidia FX 5200.
If you are using MythTV version 0.18 and you experience severe OSD stutter or flicker when XvMC is enabled, try upgrading to 0.19. The OSD flicker is fixed for the author in 0.19 with an Nvidia FX 5200.<BR>
Flicker can also be a side effect of using bob deinterlacing when the refresh rate of the monitor doesn't
match the video. Check if you are using the bob deinterlacer and if so try a different one.
=== Greyscale OSD (NVidia 4 & 5) ===
=== Greyscale OSD (NVidia 4 & 5) ===

Revision as of 13:15, 1 November 2007

Wikipedia has an article on:

X-Video Motion Compensation, or XvMC, is a part of The X Window System which allows video programs to offload motion compensation and iDCT (Inverse Discrete Cosine Transform) portions of MPEG-2 decoding to the GPU hardware. XvMC can greatly reduce CPU utilization when playing back MPEG-2 video. In theory it should also reduce bus bandwidth requirements. Savings will be most dramatic with slow CPUs or when playing HDTV. SDTV will benefit as well, but most modern CPUs can already play back SDTV without XvMC. MythTV can be compiled to use XvMC for native playback. External players such as Xine and Mplayer can also be compiled to support XvMC.

Currently, only MPEG-2 is supported. This is usually a hardware limitation. As an exception, one of the Unichrome chips is capable of XvMC accelerated MPEG-4 playback, but the Unichrome driver doesn't support that functionality at the time of this writing.

A new video acceleration API is being developed, in an effort lead by Intel. This new API supports more complete offload (VLD) as well as iDCT+MC, and can support acceleration of MPEG4, H.264, VC-1, as well as MPEG2. The site for this effort is: http://www.freedesktop.org/wiki/Software/vaapi


Each hardware video card capable of XvMC video acceleration requires a software driver to enable these features. Below is a list of the recommended software drivers and driver versions for each supported hardware type.


There are currently two X11 Nvidia drivers available: Open Source and Proprietary Binary. However, most, if not all people running an Nvidia card with MythTV use the binary driver. See below for an explanation of each driver. Recent NVidia cards have support for full MPEG-2 offload (iDCT + MC), and even MPEG-4 offload not addressed in XvMC. The GeForce4 MX and GeForce FX series cards also support full MPEG2 offload. The GeForce 4 (non-MX) series cards and earlier support only hardware motion compensation, not the more CPU intensive iDCT offload.

Proprietary Binary

Status This driver is full featured and actively maintained and developed directly by Nvidia Corp. Unless otherwise noted, any mention of Nvidia hardware on the MythTV wiki, forums, or mailing lists usually imply the use of the binary Nvidia driver.
Supports XvMC? YES
How to Obtain? This driver is not included with the XOrg X11 Server for licensing reasons. It is available as a third party download. Usually your linux distribution will have a package available in RPM, Deb, ebuild, or other format.
Recommended Version As of 2006-04-7, the currently recommended driver version is: 1.0.8756 as it fixes the OpenGL Vsync issues present in earlier versions, as well as fixing the AGP + XvMC issues on 6200 series cards.

Versions between 1.0.7676 and 1.0.8756 (exclusive) have broken OpenGL Vsync. These versions are still usable so long as OpenGL Vsync is disabled in mythfrontend's settings. One user, Trevarthan, reports that version greater than 1.0.8178 prevent a kernel panic while running mupen64.

I tested XvMC with the 8756 driver on a Geforce 6150 based motherboard (the Asus A8N-VM CSM) and it works fine with MythTV at about 10% CPU usage using a Athlon64 3200+ --Seanyseansean 11:04, 10 April 2006 (UTC)

The 9631 version is the final release that supports integrated Geforce 4 MX graphics chipsets. It's also the first driver I've tried that doesn't cause hardware lockups during XvMC playback on my hardware, so I'm happy with it.

X11 driver name nvidia
Chipset Availability Nvidia Chipsets are widely available and can be found commonly on PCI, AGP, and PCI-e cards, as well as on motherboards with integrated video, though significantly less common on the latter.

Open Source

Status Basic functionality. Only supports 2D hardware acceleration. (no 3D/OpenGL acceleration)
Supports XvMC? NO
How to Obtain? Included with the XOrg X11 Server.
X11 driver name nv


"Unichrome" is the product name for the onboard graphics of Via chipsets. The Unichrome chips can provide MPEG processing beyond standard XvMC MPEG-2 acceleration. This is called VLD (Variable Length Decoder) acceleration and is commonly referred to as XvMC VLD. XvMC VLD can provide full MPEG2 decoding, allowing MPEG playback with very low CPU requirements. Most chipsets are limited to 1024x1024 playback resolution, and thus cannot support HDTV. This includes many of the chipsets sold as "Pro" models, so take care to confirm HD support before purchase.

The Xorg via driver includes support for XvMC for both unichrome and unichrome-pro chipsets, however new chipset support is implemented in the openchrome svn first. As of July 2007, the openchrome project driver has been renamed to openchrome_drv.so and the Driver line in xorg.conf should say 'Driver "openchrome". The via driver continues to exist and the libraries are still 'libvia...'.

Support for MPEG-4 and also IDCT/MC acceleration are currently in progress. The OpenChrome project has support for a broad range of chipsets.

CN400 and PM800 chipsets are reported to support HDTV resolutions on VGA/DVI outputs. These are usually referred to as "Pro" chipsets. Many Pro chipsets ship with TV encoder chips that are not capable of displaying HDTV resolutions. These chipsets can typically playback HDTV on VGA/DVI, but not TVOUT. Pro chipsets that include a vt1625 HDTV encoder are physically capable of displaying HDTV resolutions via Component and SVid/Composite outputs. However, the openchrome project does not yet support the vt1625 so this functionality cannot be used. Of the TVOUT interfaces mentioned above, only Component is actually capable of displaying HDTV resolutions. Composite and S-video do not have the bandwidth, so your HDTV video will be scaled to SDTV resolutions. Note also that a response to a pre-sales technical support inquiry regarding the DVI daughterboards indicates they are limited to a maximum resolution of 1600x1200. Thus it seems that if you planning on using DVI that you will be limited to a maximum standard HD resolution of 720p (1280x720) output.

Preliminary testing shows that using MythTV 0.20-fixes SVN revision 12290 with XvMC-VLD for 720p ATSC source material playback is working on a SP13000 EPIA board which includes a CN400 chipset. The system is running FC6 with the openchrome driver that it ships with and the output is via VGA. CPU utilization is currently less than 40%. Many tweaks were performed to get acceptable playback and testing is taking place to determine exactly which ones were really necessary. At this point it seems like the single most important change was using the Greyscale OSD (Unichrome) tip which dramatically decreased CPU utilization and was a major factor in eliminating dropped frames and cleaning up the audio. The system is still a work in progress and work is not complete but the system has been perfectly stable although it has seen limited use to date. Unfortunately, 1080i source material playback does not appear to work as the video appears as a solid blue image. The same system is able to play both 720p and 1080i source material from an NFS mount without any problems when using Xine and the CPU utilization is under 20%. According to Trac ticket 3035 at http://svn.mythtv.org/trac/ticket/3035 the reason for the failure with 1080I is that Myth attempts to create 16 buffers, and this cannot be done within the available memory. However, a patch which reduces the buffers to 12 or even 10 allows 1080i playback. To make use of the patch you basically need to be running SVN as the code must be altered.

(Compilation of mythtv can fail with ld reporting that it cannot find either -lviaXvMCPro or -lviaXvMC. This is a bug in ld where it looks for a file named 'libviaXvMCPro.so' and ignores 'libviaXvMCPro.so.1.0.0. To correct this make a sym-link to libviaXvMcPro.so.1.0.0 called libviaXvMCPro.so.)

Trevarthan has tested HDTV on SP8000E and SP13000 EPIA boards which include a CN400 chipset. HDTV playback via VGA works without audio in Xine (a bug in Xine?). In mplayer, video and audio work, but playback isn't as smooth as in Xine, and the audio and video quickly lose sync. In MythTV 0.19, HDTV playback using XvMC VLD is broken. Audio can be heard, but the video appears as a blank or noisy dark blue screen.

SDTV playback on these boards works fine in Xine/mplayer/MythTV.

Trevarthan has also noticed considerable instability on the SP series boards with the CN400 chipset. The instability is much worse in Xine, but appears to be present in mplayer and MythTV also. It manifests as a complete hardware lockup. One of the openchrome project's developers, Ivor, has confirmed that this is a known issue with CN400 support. Guzzloid confirms this and recommends the use of a well-supported PCI graphics card (e.g. nVidia FX5200) and a dual-PCI riser instead until the driver has been fixed. (Also, do not use an active riser on SP motherboards if you are using a Hauppauge tuner card -- use the VIA EXT-PCI instead.)

Status 2D, 3D and Xv supported in Xorg via driver for CLE266, KM400/KN400, K8M800/K8N800, PM800, P4M800, P4M800PRO, and CN400 chipsets. PM8X0 likely but not available yet.
Supports XvMC? YES
How to Obtain? Included in recent versions of Xorg (6.9 and 7.0) (Newer chipsets supported in openchrome-svn first.)

minimyth is also a good source of openchrome support as it is designed to run on Via EPIA boards with Unichrome chipsets.

Recommended Version Xorg (6.9 and 7.0)
Chipset Availability A common frustration among MythTV users is that while these chipsets have Open Source drivers available, they aren't available in PCI, AGP, or PCI-e cards. They can only be found on motherboards with integrated video chipsets.
The DeltaChrome graphics cards should fill this gap but aren't widely available yet.

A standalone card is currently available on PCI-e capable boards: S3_Chrome-s27 is its current homepage.

Intel 8xx/9xx

The X11 i810 driver supports the full range of Intel integrated graphics chips. These are common in midmarket laptops and also on a number of motherboards. Their graphics capabilities are modest but underestimated by many. A binary driver containing additional functionality is available from Intel but the vast majority of the chipset's features are available from the in-tree driver. More updated information on Intel drivers/chipsets can be obtained from Intel

Status Full featured driver. Supports 2D and 3D hardware acceleration.
Supports XvMC? YES (Supports offload of Motion Compensation, but most chipsets do not support the more CPU intensive iDCT. The G965 / GMA X3000 has full iDCT+MC hardware. Driver support for this is unknown. )
How to Obtain? Included with both the X.Org and XFree86 server software.
Recommended Version Unless you are having problems, use the driver included with your distribution. A "test driver" is available from the maintainer's page. It is updated every few weeks.
X11 driver name i810
Chipset Availability This chipset is used in some DIY motherboard kits but is more common in laptops. Its use in a MythTV setup is less than ideal due to limited decoding capabilities (see above), as well as incomplete TV-Out support in the X.org/XFree86 driver.

This driver needs 'Option "XvMCSurfaces" "7"' in the Device section of xorg.conf to enable xvmc. This applies to the intel driver also. If you get a blue screen but you can hear the soundtrack, you will need to add 'Option "LinearAlloc" "16384"' to the Device section. This increases the allocated memory above the default of 6144. Note that xorg.0.log reports that it ignores the XvMCSurfaces line in xorg.conf. 'Option "Cachelines" "2048"' is reported to help with certain versions of both the i810 and intel drivers. Its presence appears to cause no adverse affects on other versions.

When set up, this driver is quite efficient. Top gave the following loading, on an Asus P5L-MX, with an Intel Core 2 Duo E6600 cpu while showing an OTA recorded 1080i HD recording.

4266 root      20   0  662m 442m 205m S   47 22.1  58:56.75 mythfrontend
3614 root      37  17  172m 116m  12m S   43  5.8  68:36.79 mythcommflag
4981 root      37  17  100m  49m  12m R   24  2.5   4:35.57 mythcommflag
3879 root      20   0  472m 155m  62m S   10  7.8   8:41.56 X

ATI Radeon

The ATI display drivers for Linux do not support XvMC. Despite the fact that all Radeon hardware has support for MPEG-2 acceleration, ATI has never provided access to these capabilities in Linux.

Application Support

Binary Distributions

The following binary linux distributions support XvMC out of the box:

  • Mandrivia 2006 Free
  • Debian


Before MythTV can make use of XvMC hardware support, it first has to be built with XvMC support.


For a more hands-on approach, one can compile MythTV directly from source.


XvMC depends upon the 'x11', 'xrandr' and 'xv' choices being enabled in configure. These are enabled by default, but you may want to specifically list them. The configure program checks for the correct libraries and files and the results are listed by the program when it exits.

If compiling manually for either nvidia, I810 or unichrome, use:

./configure --enable-xvmc

If you are compiling for unichrome-pro, use:

./configure --enable-xvmc --enable-xvmc-pro --enable-xvmc-vld

If you have the libXvMCW wrapper installed, then it will be automatically enabled by the configure program and all of the available library assets will be utilized. However, double-check your ./configure output during MythTV configuration state whether it says "yes" after "XvMC support" (or XvMC pro support) or not, since some distributions do not enable XvMC automatically regardless of XvMC library found in /usr/lib.


You may receive an error saying that the compiler cannot find xvmc.h or xvlib.h, you will need to make sure that the right packages are installed.

This can be installed using:

apt-get install libxvmc-dev
apt-get install libxv-dev

If installing MythTV on Gentoo Linux, make sure VIDEO_CARDS is properly configured in /etc/make.conf to include, "i810", "nvidia" or "via". The "xvmc" USE flag is also required. These flags can usually be set on a per package basis in /etc/portage/package.use, for example:

$ cat /etc/portage/package.use
media-tv/mythtv xvmc

Or globally for all packages in /etc/make.conf via USE="xvmc"


After MythTV has been installed, it needs to be configured to utilize XvMC.

  1. Add your XvMC library module name to the /etc/X11/XvMCConfig file, creating a new one if necessary
    1. For binary Nvidia drivers, the contents of XvMCConfig should be "libXvMCNVIDIA_dynamic.so.1"
    2. For i810 use 'libI810XvMC'. For Via chipsets use 'libviaXvMC' or 'libviaXvMCPro'.
  1. In MythTV's frontend menus, please navigate to:
    Setup -> TV Settings -> Playback
  2. Next, change the "Preferred MPEG2 Decoder" to "Standard XvMC"
  3. For the Via Unichrome or Unichrome-Pro chipsets, select "Via XvMC"
  4. Make sure "Extra audio buffering" is checked.

That's it! XvMC should be enabled. Now play a few Recordings and see what happens. If problems occur, check the Tips and Tricks section below for more info.


MPlayer includes an XvMC output plugin. To use it, try this:

mplayer -vo xvmc -vc ffmpeg12mc

(assuming you are running mplayer with XvMC support compiled in)

  • Note - unichrome support in mplayer requires a patch.


Xine's has two plugins for XvMC support, the first is named xvmc as you would expect, however to take advantage of XvMC acceleration on nVidia graphics cards using the nVidia binary drivers they have a seperate plugin named xxmc (xx instead of xv).

To use Xine with XvMC support for most graphics cards use:

xine -V xvmc 

To use Xine with XvMC support nVidia graphics cards use:

xine -V xxmc 

(assuming, of course, that xine has been compiled with XvMC support.)

Example CPU Savings

CPU RAM Video Card Content CPU w/XvMC CPU w/o XvMC XvMC Deinterlace Non-XvMC Deinterlace MythTV Version Notes
C7 Esther 1.2 GHz (Via EN12000-EG fanless) DDR2 512MB Unichrome Pro IGP (CN700) TV encoder VT1625 SD (TV-Out: PAL, S-Video@1024x768, LCD-Out: VGA@1680x1050) 25%-30% 70-80% bob 2x Kernel ? svn rev ?? don't remember (0.20 svn dev) This is a combined Front/Back-end system. Stable, reliable and smooth playback with libviaXvMCPro from openchrome. Some prebuffering pauses when switching channels or OSD text, but not systematic (using realtime video thread capability).
C3 Samuel 2 600Mhz 256MB Via CLE266 w/ VGA Out to 960x600 (ws-LCD) SD 45%-50% 100% bob No svn rev 10180 This is a combined Front/Back-end system. Stable, reliable and smooth playback with XvMC, unusable without.
AMD Athlon 800 768MB PC100 Nvidia Geforce4 MX440 SD 15%-20% 45-50% Bob/Kernel Kernel 0.18.1 A little jumpy for ~15 seconds after entering LiveTV/Recording, then smooth.
750mhz P3 w/256k cache 384M PC100 128M Nvidia 5200 AGP 2x w/S-video Out to CRT TV SD 60% 75% Bob 2x Linear Blend 0.20 release This is R5E50 KnoppMyth. SD Playback is smooth and reliable.
933mhz P3 w/256k cache 512M PC133 128M Nvidia 5200 AGP 4x w/VGA Out to 1280x1024 CRT SD 32% 40-46% NO NO 0.19 SVN fixes rev 9591 SD Playback is smooth and reliable. Frontend is remote via 100BaseTX and complains of constant prebuffer pauses. Using nvidia driver version 8756 and OpenGL VSync. XV picture controls ON.
933mhz P3 w/256k cache 512M PC133 128M Nvidia 5200 AGP 4x w/VGA Out to 1280x1024 CRT HD 1080i 100% 100% NO NO 0.19 SVN fixes rev 9591 This machine is too slow for 1080i, even with XvMC. 1080i is choppy and unwatchable. Frontend is remote via 100BaseTX and complains of constant prebuffer pauses. Using nvidia driver version 8756 and OpenGL VSync. XV picture controls ON.
AMD Duron(tm) 950 512MB GeForce4 MX 440 AGP 8x SD 12-14% 28-32% No No 0.19 Slackware 10.2 I needed to add a newer version of the X11-devel package to get the xvmc include files.
1 Ghz AMD TBird 256MB DDR 64MB GeForce4 MX 440 HD (1080i) 65-70% 100% Bob Bob LFS & compiled .19 fixes branch OSD is in B&W, but 1080 is smooth and watchable, with the occasional stutter when switching channels on live, or the OSD is on. Frontend still complains of the occasional prebuffer pause. Without XvMC, HD stutters a lot.
VIA C3 Nehemiah 1GHz 20% Unknown Unknown Unknown can hardly play mpeg2 without XvMC
Via C3 Nehemiah 1.33GHz 1GB VIA CN400 SD 25% 90% Bob Unknown 0.18.2, 0.19
AMD Athlon XP 1600 1GB DDR Nvidia 6800LE SD 15% 25% Unknown Unknown N/A, tested with MPlayer
AMD Athlon(tm) XP 1900+ 512 MB NV25 [GeForce4 Ti 4400] SD 55% 44% Bob Kernel 0.19 Debian Unstable Nvidia 8178. Picture stuttered after 0.18.1 -> 0.19 upgrade, tried XvMC fixes picture, but uses more CPU (?) Using ChromaKey Hack with success. Prebuffer pause only at begining of watching TV.
2 Ghz Celeron 512MB DDR 128MB NVidia 6200 AGP 8X HD (1080i) 65-70% 100% Bob Bob FC4 & ATRPMS 0.18.1 / LFS & compiled .19 fixes branch OSD is in B&W, but 1080 is smooth and watchable, with the occasional stutter when switching channels on live, or the OSD is on. Also had to turn on NvAGP to get XvMC working with this video card. Frontend still complains of the occasional prebuffer pause. Without XvMC, HD stutters a lot.
2 Ghz Celeron 512MB DDR 64MB GeForce4 MX 440 SD 12-14% 22-24% Bob Bob ATRPMS 0.18.1 AverMedia M179 tuner card, NVidia driver 7676, OSD is B&W
Athlon XP 2000+ 512MB PC2700 GeForce4 MX440 SD 13%-19% 25%-28% NO NO 0.18.1
Athlon XP 2000+ 512MB PC2700 GeForce4 MX440 HD 52%-62% 99%+ NO NO 0.18.1
Intel P4 2.26 512MB GeForce 5200 1080i 50% 100% Bob Any 0.19 1080 unwatchable without XvMC. 720 and below are OK withouth XvMC
AMD Athlon XP 2400 512mb DDR 3200 Nvidia FX 6200 HD (1080i) 20-25% 80% BOB Unknown 0.18 of course XvMC still likes to lock on "prebuffer" a lot
AMD 2500+ 1GB FX5500 256MB HD 50% 99%+ Unknown Unknown Unknown
AMD 2500+ OC'ed to 3200 512 MB@252 mHz FX5200 128MB HD 90+% N/A Linear N/A .2 bareley plays 1080i, and wont at all if i use anything other than linear deinterlacing. cant watch live tv. only prerecorded shows.
Sempron64 2500 256 MB PC 3200 FX 5200 HD 30% 90% Bob Bob 0.19 FC4 i386 build (still can't get x64 build to install properly). 1080 content unwatchable without XVMC, 720 / 480 content watchable w/o XVMC. With XVMC: 1080 watchable while also recording two additional 1080 channels.
P4 @ 2.67GHz 512 MB PC 3200 FX 5200 HD 1080i 45% 95% Bob Bob 0.19 FC3 ATRPMS NVidia 7676. Unwatchable without XVMC; slight, but occasionally noticable audio stutter with XVMC.
Athlon XP 2800+ 512 MB 3200 GeForce4 MX440 SD 7%-8% 9%-10% Bob Bob 0.19 Gentoo kernel 2.6.15 with NVidia 7676 driver. Tried 8178 driver, but CPU usage went to 85%
2.93Ghz Celeron D 1Gb DDR 3200 128M Nvidia FX 5200 AGP 8x w/TV OUT to 800x600 SD TV SD 8-12% 10-14% NO NO 0.19 SD Playback is smooth and reliable. No complaints!
2.93Ghz Celeron D 2Gb DDR 3200 256M Nvidia 6200 AGP 8x w/DVI Out to 1360x768 LCD SD 14% 17% NO NO 0.19 SVN fixes rev 9591 OSD is in B&W, but SD is smooth and watchable, with a very brief stutter when switching channels on LiveTV. No prebuffer pauses. Without XvMC, SD playback is smooth. Using nvidia driver version 8756 and using OpenGL Vsync. Can't reliably run Bob deinterlace for unknown reasons. XV picture controls ON.
2.93Ghz Celeron D 2Gb DDR 3200 256M Nvidia 6200 AGP 8x w/DVI Out to 1360x768 LCD HD 1080i 50% 100% NO NO 0.19 SVN fixes rev 9591 OSD is in B&W, but 1080i is smooth and watchable, with the occasional stutter when switching channels on LiveTV, or the OSD is on. Frontend still complains of the occasional prebuffer pause. Without XvMC, HD stutters a lot. Using nvidia driver version 8756 and using OpenGL Vsync. Can't reliably run Bob deinterlace for unknown reasons. XV picture controls ON.
Athlon 64 3200+ 768MB PC2700 GeForce FX 5200 HD 720P 20% 51% Bob No Pre 0.19 SVN Running in 64 bit mode, with NVidia 7676 driver
Athlon 64 3200+ 768MB PC2700 GeForce FX 5200 HD 1080i 42% 70% Bob No Pre 0.19 SVN Running in 64 bit mode, with NVidia 7676 driver
Athlon 3200+ 512MB PC3200 GeForce FX 5500 HD 1080i 45% 100% Bob Bob Pre 0.19 SVN (8922) 720p Playback with NVidia 7676 driver. Significant stuttering w/o XvMC.
Athlon 64 X2 3800+ 512MB DDR400 GeForce 6150 on-board an Asus A8N-VM CSM HD 1080i 20% 50% Bob Kernel 0.19 XvMC has some glitches. Perfect without XvMC.
Athlon 64 2400+ 512MB DDR266 Nvidia FX5200 & Asus A7V-266EX SD 20% 70% Bob Kernel 0.19 svn Picture quality is flawless, no problems. Slight errors and pauses with HD material (CPU 100%)
AMD Sempron 3400+ 768MB PC3200 Nvidia Geforce 6100 onboard (410) HD 1080i 75% 100% Linear none 0.19.129 FC5, unwatchable without Xvmc, needs latest Nvidia drivers (8756) for onboard 6100.  %75 is just to play, takes another ~%10 to record the HD from the firewire on an LVM. OSD is in color, overlay causes slight audio corruption but goes away once the overlay stops.
AMD Athlon XP 3000+ 512MB PC3200 Nvidia FX5200 HD 720p ~33% ~70% Bob Bob svn 10469 As above, audio stutters when OSD is diplayed but otherwise smooth and nice looking. Using Chromakey hack for color OSD.
AMD Athlon XP-M 3000+ (2.2GHz) 768MB PC133 Nvidia 6200 128MB DDR HD 1080i/720p 55/38% 100/90% Bob Bob 0.20 svn 11499 1080i: studders badly w/o XvMC. Minor tearing even with OpenGL sync. Displayed at 1080i w/o bob fails to consistently order interlaced fields correctly. 720p: perfect displayed at 720p w/ or w/o XvMC. Monitor: 1080i/720p/480p CRT.
AMD Athlon XP 3000+ 512MB PC3200 Nvidia FX5200 HD 1080i ~70% 100% Bob Bob svn 10469 Stuttering w/o XVMC, but with XVMC smooth and nice looking.
AMD Athlon XP 1600+ 512MB Nvidia FX5200 AGP HD 1080i/HD 720p ~60-80% 100% Onefield Onefield 0.19-fixes 10686 Haven't tried Bob deint yet. HD stutters badly without XVMC, with XVMC 1080i plays back perfectly.
AMD Athlon XP 2500+ 1GB FX5200 256MB HD 33.5% 67%+ Bob Bob 0.19-fixes Knoppmyth R5C7 Using latest Nvidia drivers 1.0-8756
AMD Athlon XP 3200+ 512MB PC3200 FX5500 256MB HD 720p/1080i 30-40% 99% Bob No 0.19-fixes Nvidia driver: 8774. B/W OSD w/ audio stuttering during OSD. Turning off "extra audio buffering" reduced audio buffer underruns. Not using NvAGP (enabling it made my CPU 90%+). Other than OSD problems, XvMC works great!
AMD 64 3500+ (2.2GHz) 1024MB DDR 400 nV 6600GT 256MB SD ~24% ? (will check later) Linear blend 0.20+SVN09-10-2006 nVidia drivers: 8774. The cpu is running at 1000MHz (cool 'n' quiet activated) during the whole time watching tv, so it is 24% @ 1000MHz. No audio buffer underruns with and without "extra audio buffering". I have to enable the "interleaved Normal" mode while watching tv to watch it perfectly. "Auto(E)" doesnt recognize the tv input as interleaved.
AMD Athlon XP 2500+ 1024MB DDR 400 nV 6200 128MB SD/HD Bob Bob svn rev 11529 Have to disable OpenGL vsync to handle 60fps progressive or 30fps interlaced (w/ bob deinterlacing) content. OpenGL vsync works fine with 24/30fps playback. OpenGL vsync with 60fps playback causes stuttering w/ prebuffering pauses, but only when OSD is not displayed - seems like a bug?
P4-2.4GHz 512MB PC2700 DDR NVidia 6200 HD Never got working 30-70% default default 0.19, 0.20 Never got XvMXC to work - it dropped every 2nd frame. FC5, complied 0.19 and 0.20 from source with --enable-proc-opt. Makes a massive difference.
AMD Athlon 2800 512MB Nvidia Geforce4 FX5200 HD 10%-15% 15-20% Bob Bob 0.20 Very smooth playback with XvMC. Stutters a little without XvMC. Didn't get Chromakey hack working. NOTE: I had 'Option "NvAGP" "3"' in my Xorg.conf, which caused the machine to crash when exiting from the EPG. (running Edgy Eft, on kernel 2.6.17-10-generic). Also had to set vsync to blank in nvidia-settings, for a smooth playback.
AMD Athlon 1800+ (1.5Ghz) 512MB Nvidia 6600GT w/Component out HD (1080i & 720p) 75% 100% Bob Bob 0.20 Without XvMC HD is choppy with audio out of sync (AC3 Pass-Through) runs at 100% CPU. With XvMC enabled 75% cpu usage and great quality. Test done with a HDHomeRun.
AMD Athlon XP 2600+ 1024 MB XFX 6600GT w/Component out dongle HD 1080i/480p 50-60% none none 0.20 Using XvMC and Option "NVAGP" "2", without the NVAGP option, I got terrible tearing.
AMD Sempron 2400+ Thoroughbred 1.667GHz 512 MB GeForce FX 5200 w/ S-video out HD 50-80% 99% Bob 2X none 0.20 Knoppmyth R5E50, Used for recording HD and watching on my parents SDTV. Can't do live TV and the OSD is almost unusable. But with XvMC playback is smooth and watchable with only occasional hiccups.
AMD Athlon XP Barton 2.0GHz (512k L2) 512 MB PC2100 (266MHz), dual channel NVidia GeForce 6200 AGP HD ~50% N/A Bob 2X N/A 0.20 XvMC, no OpenGL vsync (caused stuttering). Combined frontend/backend machine, remote mysql. Displaying on 1360x768 LCD tv, VGA cable. nForce2 motherboard. Gentoo, gcc 3.4.6, glibc 2.5, nvidia-drivers-1.0.9755-r1 (lower CPU usage), kernel 2.6.20, preempt, 300Hz timer frequency, AC-3 passthrough via SBLive card.
(Please add your example Hardware stats here!)
AMD64 Sempron 3000+ 512 MB PC3200 GeForce 6200 (AGP) 256 MB Fanless HD 50-80% 100% Bob 2X Bob 2X 0.20.2 Separate frontend and backend machines. Displaying 720p via a DVI to HDMI cable. Running Fedora 7 w/ atrpms and optical audio out w/ AC3 passthrough. Without XvMC, HD was unwatchable. Option "UseEvents" "true" and Option "NvAGP" "2" set for the nvidia drivers within xorg.
AMD64 X2 AM2 3800+ EE SFF 1024 MB DDR2-800 Single Channel GeForce 6150 (integrated on Asus M2NPV-VM) SD 23% 59% Bob 2X Bob 2X SVN (r14586) Backend/Frontend together on one machine. S-Video connection to TV. OSD is black and white. NvAGP=1
AMD Athlon 64 X2 6000+ 2GB PC2 6400 Nvidia 7300LE HD 720p & 1080i NA 35-40% NA Bob Mythdora 4.0 / MythTV 0.20.2 No problems playing back HDTV sources at 1080p resolution.

Tips and Tricks

XvMC sounds like a dream come true for those wanting to play HD content with a slower system, but unfortunately it's not always perfect. Even with XvMC and low CPU usage, many still experience problems with prebuffering pauses, mild to moderate audio or video stuttering, problems with the OSD, and other issues. If their CPU is fast enough, many simply turn off XvMC as a last resort. But this guide hopes to help the reader make the most of XvMC and avoid frustration. Here are some suggestions that may help:

Prebuffering Pause or stutter with Nvidia

  • Try disabling OpenGL VSync (this is a parameter that you can set when compiling mythtv from source - it defaults to off in v0.19)
  • Try using the 'nvidia-settings' control panel to disable Video Texture Adapter and/or Video Blitter Adapter "Sync to VBlank" checkboxes (on the "X Server XVideo Settings" page)
  • Try setting this in your "Device" section in your xorg.conf:
Option "NVAGP" "1" 

Note, some users have had better success setting NVAGP to 2 rather than 1.

  • NVidia setting: Option "UseEvents" "True" has helped many people with XvMC. Appears to lower X server CPU usage.
  • Use BOB (2x framerate) deinterlacing
  • Try disabling 'Use video as timebase' (TV Settings -> Playback)
  • Try using 'Seperate video modes for GUI and TV playback' to set your resolution to match the resolution of the recording.

Note that this section is for Video Stutter, not audio stutter.

OSD Flicker

If you are using MythTV version 0.18 and you experience severe OSD stutter or flicker when XvMC is enabled, try upgrading to 0.19. The OSD flicker is fixed for the author in 0.19 with an Nvidia FX 5200.
Flicker can also be a side effect of using bob deinterlacing when the refresh rate of the monitor doesn't match the video. Check if you are using the bob deinterlacer and if so try a different one.

Greyscale OSD (NVidia 4 & 5)

MythTV version 0.19 ships with a hack to enable full color OSD with XvMC enabled on Nvidia 4 & 5 series cards ONLY.
(i.e. Nvidia FX 5200 is a 5 series card, 6000 is a 6 series card)

Warning.png Warning: if you have a non-nvidia card or an nvidia 6 or 7 series card this hack won't help. The nvidia 6 and 7 series cards lack the chroma keying and color & contrast adjust features that the older 4 and 5 series cards had. That is why this guide refers to this feature in 0.19 as a "hack".</font>
(Thanks to Daniel Kristjansson, the author of the chromakey code, for this info!

If you have an nvidia 4 or 5 series card, please read on:
The hack is disabled by default. The code change is described here.

To enable the hack under 0.19, do this:

  • Make a change to your xorg.conf file. Add this to your Devices section:
Option "XvmcUsesTextures" "false" 
  • Make a change to the "settings" table in MythTV's MySQL database. You can access your MySQL mythconverg database from the command line like this:
mysql -u root -p mythconverg

You will be prompted for a password. If you don't remember setting one up, try just pressing the ENTER key.

Here is the SQL statement you should use to make the change:

INSERT INTO settings SET value='UseChromaKeyOSD',data='1',hostname='yourhost';

But change 'yourhost' to the hostname that your frontend is running on. If you're not sure what your hostname is, run `hostname` on the command line to find out.

Make sure you have the Composite/Damage X11 extension disabled. In your xorg.conf file (/etc/X11/xorg.conf) look for a line like this:

Section "Extenstions"
  Option "Composite" "true"

and change it to this:

Section "Extenstions"
   Option "Composite" "false"

See this thread for details.

  • Now restart X11 (for the xorg.conf change to take effect) and your frontend (for the SQL change to take effect) and see if it works!

Greyscale OSD (Unichrome)

The hack for Nvidia cards described above and shipped with MythTV version 0.19 will also work if you are using a Unichrome chipset. The hack has been verified on a Via EPIA M10000 board with the CLE266 chipset with viaXvMC enabled.

At least on UnichromePro (CN400) with 0.20-fixes SVN revision 12290, this hack seems to make a tremendous difference in the CPU utilization even during normal playback when no OSD is being displayed. Enough so that it seems to be a necessary part of making HDTV playback possible on the system.

Use XvMC For HD Only

To use ffmpeg as your decoder for all content less than 720x*, insert a row into settings where value = 'UseXvMCForHDOnly' and data = '1' such as with the following SQL command:

INSERT INTO settings (value,data,hostname) VALUES ('UseXvMCForHDOnly', '1', 'yourhost');

Naturally, substitute your frontend's host name for 'yourhost'. Be sure your frontend has PreferredMPEG2Decoder set to Standard XvMC.


  • BOB and onefield are the only Deinterlacing methods that work with XvMC.
  • Picture in Picture, or PiP, doesn't work with XvMC.
  • Editing a video is difficult to impossible with XvMC.
  • Stepping though the video frame by frame can cause artifacts with XvMC.

Hardware acceleration processes not yet supported by XvMC

XvMC does have the potential for more than it currently features it supports today. Modern graphic processors (since the DirectX 9 generation and newer) support more than just accelerating motion compensation and iDCT, and they can support more video formats than only MPEG-2 as XvMC does today. NVIDIA's PureVideo Technology and ATI's AVIVO Technology support hardware accelerated video decoding for MPEG-2, MPEG-4 AVC (H.264), and WMV3 (often referred to as WMV9 because Microsoft released it as the same time as Windows Media Player 9). Unfortunate, neither NVIDIA or ATI have yet to open up those technologies to Linux nor the API documentations to the open source community, and no publicly known attempt to reverse engineer access to those APIs have been made.

As a temporary (or permanent) solution to this, shaders in and/or Cg code could be written for these processes and added to the XvMC library to gain some of the additional advantages that GPU assisted video decoding brings and Shader Model 3.0 based GPUs can support today. (Best would be if FFmpeg was used as a reference codec and player/utility). Both NVIDIA and ATI have extensive tools for creating and maintaining the process of developing shaders easier than it has been in the past.

Processes that can be accelerated for most video formats

  • Motion compensation (mo comp)
  • Inverse Discrete Cosine Transform (iDCT)
    • Inverse Telecine 3:2 and 2:2 pull-down correction
  • Bitstream processing (CAVLC/CABAC)
  • in-loop deblocking
  • inverse quantization (IQ)
  • Variable-Length Decoding (VLD)
    • More commonly known as slice level acceleration
  • Spatial-Temporal De-Interlacing
    • Plus automatic interlace/progressive source detection


There are alternative methods for hardware assisted MPEG-2 playback of standard definition video:

External Links