Xf86-video-v4l - Revision history

CityK: add title lowercase and categories

2011-02-13T19:09:06Z

add title lowercase and categories

← Older revision		Revision as of 19:09, 13 February 2011
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		+	{{lowercase\|xf86-video-v4}}
	{{Note\|There are portions of this article that are straight verbatim of content parsed from several different sources (cited inline or referenced at the end in the article's external links) -- that notable content has just been logically stitched together to form a more comprehensive overview of the topic.}}		{{Note\|There are portions of this article that are straight verbatim of content parsed from several different sources (cited inline or referenced at the end in the article's external links) -- that notable content has just been logically stitched together to form a more comprehensive overview of the topic.}}

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	* [http://linux.die.net/man/4/v4l online copy of the video-v4l manpage]		* [http://linux.die.net/man/4/v4l online copy of the video-v4l manpage]
	* [http://www.x.org/wiki/Development/Documentation/Glossary Xorg wiki]		* [http://www.x.org/wiki/Development/Documentation/Glossary Xorg wiki]
		+
		+	[[Category:Drivers]]
		+	[[Category:Software]]

CityK: /* In Conclusion */ minor filler edit

2011-02-13T18:56:56Z

In Conclusion: minor filler edit

← Older revision		Revision as of 18:56, 13 February 2011
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	===In Conclusion===		===In Conclusion===
-	Its not an "out of the box" experience, as there are a number of requirements to get video-v4l to work properly. Though, a number of test cases have been examined with the newly revamped version of the driver, and, when you line up all the stars so to speak, it does indeed seem to work correctly as intended [http://lists.x.org/archives/xorg-devel/2011-February/019180.html].	+	By any means, Its not an "out of the box" experience, as there are a number of requirements to get video-v4l to work properly. Though, a number of test cases have been examined with the newly revamped version of the driver, and, when you line up all the stars so to speak, it does indeed seem to work correctly as intended [http://lists.x.org/archives/xorg-devel/2011-February/019180.html].

	==In the Future...==		==In the Future...==

CityK: /* In Conclusion */ insert colloquial jargon

2011-02-13T18:55:50Z

In Conclusion: insert colloquial jargon

← Older revision		Revision as of 18:55, 13 February 2011
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	===In Conclusion===		===In Conclusion===
-	Its not an "out of the box" experience, as there are a number of requirements to get video-v4l to work properly. Though, a number of test cases have been examined with the newly revamped version of the driver, and it does indeed seem to work correctly as intended [http://lists.x.org/archives/xorg-devel/2011-February/019180.html].	+	Its not an "out of the box" experience, as there are a number of requirements to get video-v4l to work properly. Though, a number of test cases have been examined with the newly revamped version of the driver, and, when you line up all the stars so to speak, it does indeed seem to work correctly as intended [http://lists.x.org/archives/xorg-devel/2011-February/019180.html].

	==In the Future...==		==In the Future...==

CityK: /* The video playback software has to make use of this interface */ drop the "tv" as its applicable to webcams etc .. any V4L device

2011-02-13T18:53:35Z

The video playback software has to make use of this interface: drop the "tv" as its applicable to webcams etc .. any V4L device

← Older revision		Revision as of 18:53, 13 February 2011
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	=== The video playback software has to make use of this interface ===		=== The video playback software has to make use of this interface ===
-	Lastly, video-v4l won't just work with any tv viewing app; rather, to actually take advantage of the V4L Xv interface provided by xf86-video-v4l, you'll also need to be using an app that supports this interface.[http://phoronix.com/forums/showthread.php?32149-xf86-video-v4l-Driver-Ported-To-V4L2/page2] Efforts have been made to bring legacy Video4Linux applications [[Tvtime]] and the 3.9x branch of [[xawtv]] up to par with V4L2 specification [http://www.kernellabs.com/blog/?p=1462 ] [http://www.mail-archive.com/linux-media@vger.kernel.org/msg27739.html] [http://www.mail-archive.com/linux-media@vger.kernel.org/msg27742.html], so, consequently, they should now be supportive of video-v4l functionality.	+	Lastly, video-v4l won't just work with any viewing app; rather, to actually take advantage of the V4L Xv interface provided by xf86-video-v4l, you'll also need to be using an app that supports this interface.[http://phoronix.com/forums/showthread.php?32149-xf86-video-v4l-Driver-Ported-To-V4L2/page2] Efforts have been made to bring legacy Video4Linux applications [[Tvtime]] and the 3.9x branch of [[xawtv]] up to par with V4L2 specification [http://www.kernellabs.com/blog/?p=1462 ] [http://www.mail-archive.com/linux-media@vger.kernel.org/msg27739.html] [http://www.mail-archive.com/linux-media@vger.kernel.org/msg27742.html], so, consequently, they should now be supportive of video-v4l functionality.

	===In Conclusion===		===In Conclusion===

CityK: /* The Graphics Adaptor device driver Must Support Xv offscreen images and putvideo functions */ minor note

2011-02-13T18:51:32Z

The Graphics Adaptor device driver Must Support Xv offscreen images and putvideo functions: minor note

← Older revision		Revision as of 18:51, 13 February 2011
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	===The Graphics Adaptor device driver Must Support Xv offscreen images and putvideo functions ===		===The Graphics Adaptor device driver Must Support Xv offscreen images and putvideo functions ===
-	Further in the chain of requirements for video-v4l to work, the gpu X driver must support Xv offscreen images '''and''' putvideo functions. Apparently not many video drivers support these. Rather, most graphics drivers in Xorg support only the XvPutImage capability [http://web.archive.org/web/20061003104218/http://etvcookbook.org/reference/mozilla.html] [http://phoronix.com/forums/showthread.php?32149-xf86-video-v4l-Driver-Ported-To-V4L2/page2] [http://www.mail-archive.com/devel@xfree86.org/msg05317.html] (You can see what your graphics device driver supports from the output of the "<code>xvinfo</code>" command).	+	Further in the chain of requirements for video-v4l to work, the gpu X driver must support Xv offscreen images '''and''' putvideo functions. Apparently not many video drivers support these. Rather, most graphics drivers in Xorg support only the XvPutImage capability [http://web.archive.org/web/20061003104218/http://etvcookbook.org/reference/mozilla.html] [http://phoronix.com/forums/showthread.php?32149-xf86-video-v4l-Driver-Ported-To-V4L2/page2] [http://www.mail-archive.com/devel@xfree86.org/msg05317.html] (You can see what your graphics device driver supports from the output of the "<code>xvinfo</code>" command. For instance, as shown in the above supplied example, only PutImage is availabe).

	=== The video playback software has to make use of this interface ===		=== The video playback software has to make use of this interface ===

CityK: minor edits

2011-02-13T18:45:33Z

minor edits

← Older revision		Revision as of 18:45, 13 February 2011
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	* tailor configurations via the particular .conf files contained in the /etc/X11/xorg.conf.d/ directory, or		* tailor configurations via the particular .conf files contained in the /etc/X11/xorg.conf.d/ directory, or
	* similar as to the case in the past, fall back to the classic/legacy method of using an xorg.conf file to set up their hardware with their X environment		* similar as to the case in the past, fall back to the classic/legacy method of using an xorg.conf file to set up their hardware with their X environment
-	The Xorg configuration precidence is: xorg.conf file (if specified) > /etc/X11/xorg.conf.d/nn-yyyyy.conf files (if specified) > automatic Xorg configuration}}	+	The Xorg configuration precidence is:<br>
		+	:xorg.conf file (if specified) > /etc/X11/xorg.conf.d/nn-yyyyy.conf files (if specified) > automatic Xorg configuration}}

	===You need to be using the new version of video-v4l===		===You need to be using the new version of video-v4l===
	Up until Feb 2011, the existing, and long neglected, xf86-video-v4l driver only supported the V4L1 API. That wasn't a roadblock in of itself because,		Up until Feb 2011, the existing, and long neglected, xf86-video-v4l driver only supported the V4L1 API. That wasn't a roadblock in of itself because,
-	:{while}this driver still supports only V4L ioctls, however it should work just fine with all V4L2 devices through the V4L2 backward-compatibility layer. Since V4L2 permits multiple opens it is possible (if supported by the V4L2 driver) to capture video while an X client requested video overlay. [http://v4l2spec.bytesex.org/spec/x16430.htm]	+	:{while} this driver still supports only V4L ioctls, however it should work just fine with all V4L2 devices through the V4L2 backward-compatibility layer. Since V4L2 permits multiple opens it is possible (if supported by the V4L2 driver) to capture video while an X client requested video overlay. [http://v4l2spec.bytesex.org/spec/x16430.htm]
	However,		However,
	:V4L1 API was dropped on kernel 2.6.38. Even the emulation layer inside kernel was dropped. While it might still be possible to use X with libv4l and a LD_PRELOADER setup, the proper way is to port the driver to use the V4L2 API.		:V4L1 API was dropped on kernel 2.6.38. Even the emulation layer inside kernel was dropped. While it might still be possible to use X with libv4l and a LD_PRELOADER setup, the proper way is to port the driver to use the V4L2 API.

CityK: /* The Technical Mumbo-Jumbo */ minor edit

2011-02-13T18:42:24Z

The Technical Mumbo-Jumbo: minor edit

← Older revision		Revision as of 18:42, 13 February 2011
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	When this driver is installed and configured properly, then an X11 client application can use the XvPutVideo function to cause a captured video stream to be directly written to the applicable screen's frame buffer or video overlay buffer. This permits the use of hardware DMA capabilities to transfer the captured video directly from {for example} a PCI {V4L} card via the PCI bus to the graphics adaptor's frame buffer memory. In contrast, if XvPutImage is used instead of XvPutVideo, then all video frames must first pass through system memory, placing a heavier burden on system memory throughput.[http://web.archive.org/web/20061003104218/http://etvcookbook.org/reference/mozilla.html]		When this driver is installed and configured properly, then an X11 client application can use the XvPutVideo function to cause a captured video stream to be directly written to the applicable screen's frame buffer or video overlay buffer. This permits the use of hardware DMA capabilities to transfer the captured video directly from {for example} a PCI {V4L} card via the PCI bus to the graphics adaptor's frame buffer memory. In contrast, if XvPutImage is used instead of XvPutVideo, then all video frames must first pass through system memory, placing a heavier burden on system memory throughput.[http://web.archive.org/web/20061003104218/http://etvcookbook.org/reference/mozilla.html]

-	So its a special generic capture driver, that	+	So, in summary, its a special generic capture driver, that:
	* works with every piece of hardware which is supported by a video4linux (kernel-) device driver … it works with any hardware supported by a Video 4 Linux (V4L) driver ... and		* works with every piece of hardware which is supported by a video4linux (kernel-) device driver … it works with any hardware supported by a Video 4 Linux (V4L) driver ... and
	* works with every piece of hardware which is able to handle video overlay.... i.e. it targets no specific graphics card and instead provides an X-Video extension port for video overlay. [http://linux.die.net/man/4/v4l] [http://www.phoronix.com/scan.php?page=news_item&px=OTA4Nw]		* works with every piece of hardware which is able to handle video overlay.... i.e. it targets no specific graphics card and instead provides an X-Video extension port for video overlay. [http://linux.die.net/man/4/v4l] [http://www.phoronix.com/scan.php?page=news_item&px=OTA4Nw]

CityK: insert references inline; some various edits -- wording, grammer etc...

2011-02-13T18:40:24Z

insert references inline; some various edits -- wording, grammer etc...

Show changes

CityK: change example xvinfo box to a floating table so page renders better

2011-02-13T17:22:49Z

change example xvinfo box to a floating table so page renders better

← Older revision		Revision as of 17:22, 13 February 2011
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	===video-v4l still (currently) only supports video overlay===		===video-v4l still (currently) only supports video overlay===
-	{\|	+	{\| align="right"
-	~~\| valign~~=~~top \|~~	+	\| <div style="border: solid 1px; border-color: blue; margin: 1em; padding: 1em; background-color: Lavender;">
-	Recall that while video-v4l is neutral/agnostic towards graphic adapters (i.e. it targets no specific graphics card) its functionality is only available to those graphic hardware which are able to handle video overlay. Most, if not all, modern graphics hardware no longer provide a traditional video overlay hardware engine, but, rather, rely upon Textured Video (part of the 3D engine) for rendering video streams. To the best of memory:	+
-	* nvidia 5xxx gpus were the last series to include a video overlay engine. All newer devices utilize texture video	+
-	* radeons had their overlay engine removed ?	+
-	* Intel, IIRC, moved to texture video exclusively with i915 and later	+
-	* SIS 300 supports overlay ... but what else ?	+
-	* Via ??...	+
-	~~And so on.~~	+
-		+
-	~~To check whether a particular feature is available to your graphics hardware, or, more correctly stated, whether it is even exposed/supported via its corresponding driver, you can use the~~	+
-	* <code>xdpyinfo </code>utility (X server display info) - checks whether the X server driver for your video adapter supports ''{feature xxxx}''' ...	+
-	The output is rather lengthy, but if you scroll up to near the very begining, it will list the number and which particular extentions are supported. If you see XVideo listed (and almost all should) you've meet the first part of the requirement to use video-v4l.	+
-		+
-	~~Next, you have to drill down to see the specifics as to how Xv is supported by your hardware and its corresponding driver. This you can do using~~	+
-	* <code>xvinfo </code>– queries the XVideo extension capabilities of the attached graphics cards ...	+
-	~~With some older hardware, before the gpu manufacturer's full transition to Texture Video, the device's driver will expose several Xv rendering methods: Blitter, Overlay Video, Texture Video, ...~~	+
-	An example of xvinfo output for a more contemporary (cirrca 2009/2010) graphics adapter/driver combination is provided on the side. Clearly the adaptor is missing Overlay Video capabilities (relying instead only upon Texture Video), so, in such a case, the video-v4l driver is not useable.	+
-	\| ~~valign=top halign=right width=30% \|~~	+
-	<div style="border: solid 1px; border-color: blue; margin: 1em; padding: 1em; background-color: Lavender;">	+
	'''Ex. xvinfo output for a combination of a Radeon 4200 GPU and the Radeon driver'''		'''Ex. xvinfo output for a combination of a Radeon 4200 GPU and the Radeon driver'''
	user:~> xvinfo		user:~> xvinfo
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	</div>		</div>
	\|}		\|}
		+	Recall that while video-v4l is neutral/agnostic towards graphic adapters (i.e. it targets no specific graphics card) its functionality is only available to those graphic hardware which are able to handle video overlay. Most, if not all, modern graphics hardware no longer provide a traditional video overlay hardware engine, but, rather, rely upon Textured Video (part of the 3D engine) for rendering video streams. To the best of memory:
		+	* nvidia 5xxx gpus were the last series to include a video overlay engine. All newer devices utilize texture video
		+	* radeons had their overlay engine removed ?
		+	* Intel, IIRC, moved to texture video exclusively with i915 and later
		+	* SIS 300 supports overlay ... but what else ?
		+	* Via ??...
		+	And so on.
		+
		+	To check whether a particular feature is available to your graphics hardware, or, more correctly stated, whether it is even exposed/supported via its corresponding driver, you can use the
		+	* <code>xdpyinfo </code>utility (X server display info) - checks whether the X server driver for your video adapter supports ''{feature xxxx}''' ...
		+	The output is rather lengthy, but if you scroll up to near the very begining, it will list the number and which particular extentions are supported. If you see XVideo listed (and almost all should) you've meet the first part of the requirement to use video-v4l.
		+
		+	Next, you have to drill down to see the specifics as to how Xv is supported by your hardware and its corresponding driver. This you can do using
		+	* <code>xvinfo </code>– queries the XVideo extension capabilities of the attached graphics cards ...
		+	With some older hardware, before the gpu manufacturer's full transition to Texture Video, the device's driver will expose several Xv rendering methods: Blitter, Overlay Video, Texture Video, ...
		+	An example of xvinfo output for a more contemporary (cirrca 2009/2010) graphics adapter/driver combination is provided on the side. Clearly the adaptor is missing Overlay Video capabilities (relying instead only upon Texture Video), so, in such a case, the video-v4l driver is not useable.
		+

	===The Graphics Adaptor device driver Must Support Xv offscreen images and putvideo functions ===		===The Graphics Adaptor device driver Must Support Xv offscreen images and putvideo functions ===

CityK: add inline reference links; minor edits

2011-02-13T03:36:09Z

add inline reference links; minor edits

← Older revision		Revision as of 03:36, 13 February 2011
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	===The Graphics Adaptor device driver Must Support Xv offscreen images and putvideo functions ===		===The Graphics Adaptor device driver Must Support Xv offscreen images and putvideo functions ===
-	Further in the chain of requirements for video-v4l to work, the gpu X driver must support Xv offscreen images '''and''' putvideo functions. Apparently not many video drivers support these. Rather, most graphics drivers in Xorg support only the XvPutImage capability. (~~See~~ the output of xvinfo).	+	Further in the chain of requirements for video-v4l to work, the gpu X driver must support Xv offscreen images '''and''' putvideo functions. Apparently not many video drivers support these. Rather, most graphics drivers in Xorg support only the XvPutImage capability [http://web.archive.org/web/20061003104218/http://etvcookbook.org/reference/mozilla.html] [http://www.mail-archive.com/devel@xfree86.org/msg05317.html] (as can be seen in the output of the "xvinfo" command).

	=== The video playback software has to make use of this interface ===		=== The video playback software has to make use of this interface ===
-	Lastly, video-v4l won't just work with any tv viewing app; rather, to actually take advantage of the V4L Xv interface provided by xf86-video-v4l, you'll also need to be using an app like [[xawtv]] that supports this interface. Efforts have been made in a couple of cases to bring legacy Video4Linux applications up to par with V4L2 specification, and, consequently, supportive of ~~the~~ video-v4l ~~functioality~~. [http://www.kernellabs.com/blog/?p=1462 Tvtime],[http://www.mail-archive.com/linux-media@vger.kernel.org/msg27739.html] and [http://www.mail-archive.com/linux-media@vger.kernel.org/msg27742.html xawtv], for instance.	+	Lastly, video-v4l won't just work with any tv viewing app; rather, to actually take advantage of the V4L Xv interface provided by xf86-video-v4l, you'll also need to be using an app like [[xawtv]] that supports this interface. Efforts have been made in a couple of cases to bring legacy Video4Linux applications up to par with V4L2 specification, and, consequently, should now be supportive of video-v4l functionality. ([http://www.kernellabs.com/blog/?p=1462 Tvtime],[http://www.mail-archive.com/linux-media@vger.kernel.org/msg27739.html] and [http://www.mail-archive.com/linux-media@vger.kernel.org/msg27742.html xawtv], for instance).

	===In Conclusion===		===In Conclusion===
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	==In the Future...==		==In the Future...==
-	video-v4l may gain a bunch of utility in the future if support for textured video can be added to the driver [http://lists.x.org/archives/xorg-devel/2011-February/019049.html] [http://lists.x.org/archives/xorg-devel/2011-February/019180.html]. This will open up the possibility of using the module (i.e. gaining the benefits it provides) with most modern graphics adaptors. However, despite the fact that some of the updated traditional apps, such as Tvtime and xawtv, will be able to make use of this extended capability, it may come just as the sun in setting in the case of using video-v4l in others; for example, MythTV development plans for version 0.26 or later call dropping Xv support in favour of other rendering methods [http://www.phoronix.com/scan.php?page=news_item&px=ODg2Mw]	+	video-v4l may gain a bunch of utility in the future if support for textured video can be added to the driver [http://lists.x.org/archives/xorg-devel/2011-February/019049.html] [http://lists.x.org/archives/xorg-devel/2011-February/019180.html]. This will open up the possibility of using the module (i.e. gaining the benefits it provides) with most modern graphics adaptors, provided the associated device driver for the hardware is also up to the task. However, despite the fact that some of the updated traditional apps, such as Tvtime and xawtv, will be able to make use of this extended capability, it may come just as the sun in setting in the case of using video-v4l in others; for example, MythTV development plans for version 0.26 or later call for dropping Xv support in favour of other rendering methods [http://www.phoronix.com/scan.php?page=news_item&px=ODg2Mw]

	==External Links==		==External Links==