XvMC - Revision history

Gamester17 at 10:22, 19 February 2008

2008-02-19T10:22:27Z

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	'''X-Video Motion Compensation (XvMC)''', is an extension of the [http://en.wikipedia.org/wiki/X_video_extension X video extension (Xv)] for the [http://en.wikipedia.org/wiki/X_Window_System X Window System (a.k.a. X11)] under Linux operating-systems. The XvMC API allows video programs to offload portions of the video decoding process to the [http://en.wikipedia.org/wiki/Graphics_processing_unit GPU] video-hardware. In theory this process should also reduce bus bandwidth requirements. Currently, the supported portions to be offloaded by XvMC onto the GPU are [[motion compensation\|motion compensation (mo comp)]] and [[inverse discrete cosine transform\|inverse discrete cosine transform (iDCT)]] for [[MPEG-2]] video. XvMC also supports offloading decoding of [[motion compensation\|mo comp]], [[inverse discrete cosine transform\|iDCT]], and VLD ("Variable-Length Decoding", more commonly known as "slice level acceleration") for not only [[MPEG-2]] but also [[MPEG-4 ASP\|MPEG-4 ASP (H.263)]] and [[MPEG-4 AVC\|MPEG-4 AVC (H.264)]] video on VIA Unichrome (S3 Graphics Chrome Series) hardware. Popular software applications known to take advantage of XvMC include [[MPlayer]], [[MythTV]], and [[xine]].		'''X-Video Motion Compensation (XvMC)''', is an extension of the [http://en.wikipedia.org/wiki/X_video_extension X video extension (Xv)] for the [http://en.wikipedia.org/wiki/X_Window_System X Window System (a.k.a. X11)] under Linux operating-systems. The XvMC API allows video programs to offload portions of the video decoding process to the [http://en.wikipedia.org/wiki/Graphics_processing_unit GPU] video-hardware. In theory this process should also reduce bus bandwidth requirements. Currently, the supported portions to be offloaded by XvMC onto the GPU are [[motion compensation\|motion compensation (mo comp)]] and [[inverse discrete cosine transform\|inverse discrete cosine transform (iDCT)]] for [[MPEG-2]] video. XvMC also supports offloading decoding of [[motion compensation\|mo comp]], [[inverse discrete cosine transform\|iDCT]], and Variable Length Decoding\|VLD]] ("[[Variable Length Decoding]]", more commonly known as "slice-level acceleration") for not only [[MPEG-2]] but also [[MPEG-4 ASP\|MPEG-4 ASP (H.263)]] and [[MPEG-4 AVC\|MPEG-4 AVC (H.264)]] video on VIA Unichrome (S3 Graphics Chrome Series) hardware. Popular software applications known to take advantage of XvMC include [[MPlayer]], [[MythTV]], and [[xine]].

	XvMC is the UNIX equivalent of the Microsoft Windows [[DirectX Video Acceleration\|DirectX Video Acceleration (DxVA) API]]. Mac OS X also includes MPEG-2 acceleration capabilities, but Apple has chosen not to expose that API for use outside their own DVD-Video player application.		XvMC is the UNIX equivalent of the Microsoft Windows [[DirectX Video Acceleration\|DirectX Video Acceleration (DxVA) API]]. Mac OS X also includes MPEG-2 acceleration capabilities, but Apple has chosen not to expose that API for use outside their own DVD-Video player application.

Gamester17: /* Processes that could be accelerated */

2008-02-19T09:59:51Z

Processes that could be accelerated

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	==Processes that could be accelerated==		==Processes that could be accelerated==
	Even though XvMC currently only support hardware acceleration of [[motion compensation\|motion compensation (mo comp)]] and [[inverse discrete cosine transform\|inverse discrete cosine transform (iDCT)]], (and Variable-Length Decoding for VIA Unichrome GPU), additional video decoding processes could be passed on to modern [[graphics processing unit\|GPU]]s which on [[Microsoft Windows]] can accelerate many more via Microsoft's [[DirectX Video Acceleration\|DirectX Video Acceleration (DxVA) API]]. XvMC could be extended in the future to support the same processes:		Even though XvMC currently only support hardware acceleration of [[motion compensation\|motion compensation (mo comp)]] and [[inverse discrete cosine transform\|inverse discrete cosine transform (iDCT)]], (and Variable-Length Decoding for VIA Unichrome GPU), additional video decoding processes could be passed on to modern [[graphics processing unit\|GPU]]s which on [[Microsoft Windows]] can accelerate many more via Microsoft's [[DirectX Video Acceleration\|DirectX Video Acceleration (DxVA) API]]. XvMC could be extended in the future to support the same processes:
	* Motion compensation		* [[Motion compensation\|Motion compensation (mocomp)]]
	* [[Inverse discrete cosine transform]] (iDCT)		* [[Inverse discrete cosine transform\|Inverse discrete cosine transform (iDCT)]]
	** [[Inverse telecine]] 3:2 and 2:2 pull-down correction		** [[Inverse telecine]] 3:2 and 2:2 pull-down correction
	* ~~Bitstream processing (~~[[~~CAVLC]]/[[CABAC~~]])		* Inverse [[modified discrete cosine transform]] (iMDCT)
	* In-loop [[deblocking]]		* In-loop [[deblocking filter (video)\|deblocking filter]]
			* Intra-frame prediction
	* Inverse [[Quantization (image processing)\|quantization]] (IQ)		* Inverse [[Quantization (image processing)\|quantization]] (IQ)
	* Variable-Length Decoding (VLD), more commonly known as slice-level acceleration		* [[Huffman_coding\|Variable-Length Decoding (VLD)]], more commonly known as slice-level acceleration
	* Spatial-temporal [[deinterlacing]] and automatic [[interlace]]/[[progressive scan\|progressive]] source detection		* Spatial-temporal [[deinterlacing]] and automatic [[interlace]]/[[progressive scan\|progressive]] source detection
			* Bitstream processing ([[CAVLC]]/[[CABAC]])

	==Current limitations==		==Current limitations==

Gamester17: /* External links */

2008-01-07T11:24:43Z

External links

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	[[Category:Freedesktop.org]]		[[Category:Freedesktop.org]]
	[[Category:Device drivers]]		[[Category:Device drivers]]
			[[Category:FFmpeg]]

Gamester17: /* External links */

2008-01-07T11:16:18Z

External links

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	[[Category:Application programming interfaces]]		[[Category:Application programming interfaces]]
			[[Category:Application layer protocols]]
	[[Category:Freedesktop.org]]		[[Category:Freedesktop.org]]
	[[Category:~~Application layer protocols~~]]		[[Category:Device drivers]]

Gamester17: /* See also */

2008-01-07T11:11:55Z

Gamester17: /* References */

2007-12-28T22:46:40Z

References

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	A project called [[Video Acceleration API\|Video Acceleration API (VA API)]] is underway to develop a more modern video acceleration API which will support the video acceleration features of modern GPUs.		A project called [[Video Acceleration API\|Video Acceleration API (VA API)]] is underway to develop a more modern video acceleration API which will support the video acceleration features of modern GPUs.

			== See also ==
			* [[XvMC\|X-Video Motion Compensation (XvMC)]]
			* [[DirectX Video Acceleration\|DirectX Video Acceleration (DxVA) API]] - Microsoft Windows equivalent to [[VA API]] and [[XvMC]]

	== References ==		== References ==

Gamester17 at 22:41, 28 December 2007

2007-12-28T22:41:51Z

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	*[http://sourceforge.net/projects/unichrome The Unichrome Project]		*[http://sourceforge.net/projects/unichrome The Unichrome Project]
	*[http://www.mythtv.org/wiki/index.php/XvMC XvMC at MythTV's wiki]		*[http://www.mythtv.org/wiki/index.php/XvMC XvMC at MythTV's wiki]

			[[Category:Application programming interfaces]]
			[[Category:Freedesktop.org]]
			[[Category:Application layer protocols]]

Gamester17 at 22:40, 28 December 2007

2007-12-28T22:40:07Z

New page

'''X-Video Motion Compensation (XvMC)''', is an extension of the [http://en.wikipedia.org/wiki/X_video_extension X video extension (Xv)] for the [http://en.wikipedia.org/wiki/X_Window_System X Window System (a.k.a. X11)] under Linux operating-systems. The XvMC API allows video programs to offload portions of the video decoding process to the [http://en.wikipedia.org/wiki/Graphics_processing_unit GPU] video-hardware. In theory this process should also reduce bus bandwidth requirements. Currently, the supported portions to be offloaded by XvMC onto the GPU are [[motion compensation|motion compensation (mo comp)]] and [[inverse discrete cosine transform|inverse discrete cosine transform (iDCT)]] for [[MPEG-2]] video. XvMC also supports offloading decoding of [[motion compensation|mo comp]], [[inverse discrete cosine transform|iDCT]], and VLD ("Variable-Length Decoding", more commonly known as "slice level acceleration") for not only [[MPEG-2]] but also [[MPEG-4 ASP|MPEG-4 ASP (H.263)]] and [[MPEG-4 AVC|MPEG-4 AVC (H.264)]] video on VIA Unichrome (S3 Graphics Chrome Series) hardware. Popular software applications known to take advantage of XvMC include [[MPlayer]], [[MythTV]], and [[xine]].

XvMC is the UNIX equivalent of the Microsoft Windows [[DirectX Video Acceleration|DirectX Video Acceleration (DxVA) API]]. Mac OS X also includes MPEG-2 acceleration capabilities, but Apple has chosen not to expose that API for use outside their own DVD-Video player application.

[[Motion compensation]] is an algorithmic technique employed in the encoding of video data, for example in the generation of [[MPEG-2]] files.

== Device drivers ==
Each hardware video GPU capable of XvMC video acceleration requires a [http://en.wikipedia.org/wiki/X_Window_System X Window System (a.k.a. X11)] software device-driver to enable these features.
===Hardware manufactures===
====NVIDIA====
There are currently three X11 Nvidia drivers available: One open source developed by the Linux community called [http://en.wikipedia.org/wiki/Nouveau_%28graphics%29 Nouveau], one 2D only open source driver maintained by NVIDIA called nv, and one proprietary binary device driver by NVIDIA. Nouveau is currently working on XvMC support [http://nouveau.freedesktop.org/wiki/SoC][http://nouveau.freedesktop.org/wiki/RequiredFunctionality], the 2D nv driver does not support XvMC, and the official [[proprietary]] binary device driver by NVIDIA only supports MPEG-2 offloading (mo comp and iDCT).

====VIA====
VIA provides open source device drivers for its VIA Unichrome (S3 Graphics Chrome Series) hardware, supporting offloading of [[MPEG-2]], [[MPEG-4 ASP|MPEG-4 ASP (H.263)]] and [[MPEG-4 AVC|MPEG-4 AVC (H.264)]] video.
Thanks to VLD level of decoding VIA offloads much more decoding tasks from CPU than GPUs supporting iDCT or mo comp levels only.

====Intel====
Intel provides official open source device drivers which supports MPEG-2 offloading (mo comp and iDCT) on Intel's 8xx/9xx range of integrated graphics chips. [http://intellinuxgraphics.org/man.html]

====ATI/AMD====
There are no device drivers which support XvMC on ATI/AMD hardware, (although all ATI/AMD Radeon GPU hardware has support for MPEG-2 acceleration on iDCT and mo comp levels).

====Matrox====
There are no device drivers which support XvMC on Matrox hardware, (although the Matrox Parhelia GPU hardware has support for MPEG-2 acceleration on mo comp level).

====S3====
Binary device driver by S3 only supports MPEG-2 offloading in initial 2.0.16 driver on Chrome 20 and up GPUs.

==XvMC API technical overview==
This is from [http://www.xfree86.org/~mvojkovi/XvMC_API.txt X-Video Motion Compensation - API specification v. 1.0]
===XvPort===
XvMC extends the [http://en.wikipedia.org/wiki/X_video_extension X video extension (Xv)] and makes use of the familiar concept of the XvPort. Ports have attributes that can be set and queried through Xv. In XvMC ports can also have hardware [[motion compensation]] contexts created for use with them. Ports which support XvImages (ie. they have an "XV_IMAGE" port encoding as described in the Xv version 2.2 API addendum) can be queried for the list of XvMCSurface types they support. If they support any XvMCSurface types an XvMCContext can be created for that port.

===XvMCContext===
XvMCContext describes the state of the [[motion compensation]] pipeline. An individual XvMCContext can be created for use with a single port, surface type, motion compensation type, width and height combination. For example, a context might be created for a particular port that does [[MPEG-2]] motion compensation on 720 x 480 4:2:0 surfaces. Once the context is created, referencing it implies the port, surface type, size and the motion compensation type. Contexts may be "direct" or "indirect". For indirect contexts the [[X server]] renders all video using the data passed to it by the client. For direct contexts the client libraries render the video with little or no interaction with the X server.

===XvMCSurfaces===
XvMCSurfaces are buffers into which the [[motion compensation]] hardware can render. The data in the buffers themselves are not client accessible and may be stored in a hardware-specific format. Any number of buffers can be created for use with a particular context (resources permitting).

===Video Pipeline===
XvMC provides video acceleration starting at one of two places in the video [[Pixel Pipelines|pipeline]]. Acceleration starting at the first point, which we shall call the "Motion Compensation" level, begins after the the [[inverse quantization]] and [[inverse discrete cosine transform|IDCT]] at the place where [[motion compensation]] is to be applied. The second point, which we shall call the "IDCT" level, begins before the IDCT just after the inverse quantization.

===Rendering===
Rendering is done by presenting the library with a target XvMCSurface and up to two reference XvMCSurfaces for the motion compensation, a buffer of 8x8 blocks and a command buffer which describes how to use the 8x8 blocks along with motion compensation vectors to construct the data in the target XvMCSurface. When the pipeline starts at the iDCT level, Xv will perform the IDCT on the blocks before performing the motion compensation. A function is provided to copy/overlay a portion of the XvMCSurface to a drawable with arbitrary scaling.

===XvMCSubpictures===
XvMCSubpictures are separate surfaces that may be blended with the target surface. Any number of XvMCSubpictures may be created for use with a context (resources permitting). Both "backend" and "frontend" subpicture behavior are supported.

==Software support==
XvMC acceleration is supported in:
* [[FFmpeg]]
* [[MPlayer]]
* [[xine]]
* [[MythTV]]
* [[VLC]]

==Processes that could be accelerated==
Even though XvMC currently only support hardware acceleration of [[motion compensation|motion compensation (mo comp)]] and [[inverse discrete cosine transform|inverse discrete cosine transform (iDCT)]], (and Variable-Length Decoding for VIA Unichrome GPU), additional video decoding processes could be passed on to modern [[graphics processing unit|GPU]]s which on [[Microsoft Windows]] can accelerate many more via Microsoft's [[DirectX Video Acceleration|DirectX Video Acceleration (DxVA) API]]. XvMC could be extended in the future to support the same processes:
* Motion compensation
* [[Inverse discrete cosine transform]] (iDCT)
** [[Inverse telecine]] 3:2 and 2:2 pull-down correction
* Bitstream processing ([[CAVLC]]/[[CABAC]])
* In-loop [[deblocking]]
* Inverse [[Quantization (image processing)|quantization]] (IQ)
* Variable-Length Decoding (VLD), more commonly known as slice-level acceleration
* Spatial-temporal [[deinterlacing]] and automatic [[interlace]]/[[progressive scan|progressive]] source detection

==Current limitations==
Besides not matching all of the features and function of [[DirectX Video Acceleration|DxVA]] (which is the [[Microsoft]] equivalent [[API]] for [[Microsoft Windows|Windows]]), and lacking support for other video formats than [[MPEG-2]] in Linux device drivers from [[ATI]] and [[NVIDIA]], the [http://www.xfree86.org/~mvojkovi/XvMC_API.txt XvMC API specification version 1.0] currently also has these other limitations:
*BOB and onefield are the only [[deinterlacing]] methods that work with XvMC.
*Picture in Picture (PiP) does work with XvMC.
*Stepping though the video frame by frame can cause artifacts with XvMC.
*Editing a video is difficult to impossible with XvMC activated.
*The client application must run as root
*Lacking network transparency in the XvMC API
*Lacking the ability for the client application to be completely independent of which client side library needs to be used (ie. a unified wrapper library).

A project called [[Video Acceleration API|Video Acceleration API (VA API)]] is underway to develop a more modern video acceleration API which will support the video acceleration features of modern GPUs.

== References ==
* http://en.wikipedia.org/wiki/XvMC

== External links ==
*[http://www.x.org X.Org Foundation]
*[http://www.xfree86.org The XFree86 Project, Inc.]
*[http://www.freedesktop.org freedesktop.org]
*[http://www.openchrome.org/ openChrome Project]
**[http://wiki.openchrome.org/tikiwiki/tiki-index.php?page=HardwareCaveats openChrome supported hardware]
*[http://sourceforge.net/projects/unichrome The Unichrome Project]
*[http://www.mythtv.org/wiki/index.php/XvMC XvMC at MythTV's wiki]

← Older revision		Revision as of 04:11, 7 January 2008
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	== See also ==		== See also ==
	* [[~~XvMC~~\|X-Video ~~Motion Compensation~~ (~~XvMC~~)]]		* [[Video Acceleration API\|Video Acceleration API (VA API)]]
	* [[DirectX Video Acceleration\|DirectX Video Acceleration (DxVA) API]] - Microsoft Windows equivalent to [[VA API]] and [[XvMC]]		* [[DirectX Video Acceleration\|DirectX Video Acceleration (DxVA) API]] - Microsoft Windows equivalent to [[VA API]] and [[XvMC]]