Hacker Guide/Video Output - Revision history

DoesItReallyMatter: Remove h1, use Template:Warning, add wikilink

2019-04-17T08:57:16Z

Remove h1, use Template:Warning, add wikilink

← Older revision		Revision as of 08:57, 17 April 2019
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	{{Back to\|Hacker Guide}}		{{Back to\|Hacker Guide}}
	~~= The~~ video output layer =		This page is about the video output layer

	== Data structures and main loop ==		== Data structures and main loop ==

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	=== picture_t ===		=== picture_t ===

	The main data structure is ''picture_t'', which describes everything a video decoder thread needs. Please, refer to those files for more information. Typically, p_data will be a pointer to YUV planar picture.		The main data structure is ''picture_t'', which describes everything a video decoder thread needs. Please, refer to those files for more information. Typically, p_data will be a pointer to [[YUV]] planar picture.

	=== subpicture_t and SPU ===		=== subpicture_t and SPU ===
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	{{fn\|picture_t * vout_CreatePicture ( vout_thread_t *p_vout, int i_type, int i_width, int i_height )\|Returns an allocated picture buffer. i_type will be for instance YUV_420_PICTURE, and i_width and i_height are in pixels.}}		{{fn\|picture_t * vout_CreatePicture ( vout_thread_t *p_vout, int i_type, int i_width, int i_height )\|Returns an allocated picture buffer. i_type will be for instance YUV_420_PICTURE, and i_width and i_height are in pixels.}}

	~~'''~~Warning~~'''~~		{{Warning\|If no picture is available in the heap, vout_CreatePicture will return NULL.}}

	If no picture is available in the heap, vout_CreatePicture will return NULL.

	{{fn\|vout_LinkPicture ( vout_thread_t p_vout, picture_t p_pic )\|Increases the refcount of the picture, so that it doesn't get accidently freed while the decoder still needs it. For instance, an I or P picture can still be needed after displaying to decode interleaved B pictures.}}		{{fn\|vout_LinkPicture ( vout_thread_t p_vout, picture_t p_pic )\|Increases the refcount of the picture, so that it doesn't get accidently freed while the decoder still needs it. For instance, an I or P picture can still be needed after displaying to decode interleaved B pictures.}}

DoesItReallyMatter: Format with Template:Fn

2019-04-17T07:59:33Z

Format with Template:Fn

← Older revision		Revision as of 07:59, 17 April 2019
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	The video output exports a bunch of functions so that decoders can send their decoded data. The most important function is vout_CreatePicture which allocates the picture buffer to the size indicated by the video decoder. It then just needs to feed (void *) p_picture->p_data with the decoded data, and call vout_DisplayPicture and vout_DatePicture upon necessary.		The video output exports a bunch of functions so that decoders can send their decoded data. The most important function is vout_CreatePicture which allocates the picture buffer to the size indicated by the video decoder. It then just needs to feed (void *) p_picture->p_data with the decoded data, and call vout_DisplayPicture and vout_DatePicture upon necessary.

	picture_t vout_CreatePicture ( vout_thread_t *p_vout, int i_type, int i_width, int i_height )~~ :~~ Returns an allocated picture buffer. i_type will be for instance YUV_420_PICTURE, and i_width and i_height are in pixels.		{{fn\|picture_t * vout_CreatePicture ( vout_thread_t *p_vout, int i_type, int i_width, int i_height )\|Returns an allocated picture buffer. i_type will be for instance YUV_420_PICTURE, and i_width and i_height are in pixels.}}

	'''Warning'''		'''Warning'''
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	If no picture is available in the heap, vout_CreatePicture will return NULL.		If no picture is available in the heap, vout_CreatePicture will return NULL.

	vout_LinkPicture ( vout_thread_t p_vout, picture_t *p_pic )~~ :~~ Increases the refcount of the picture, so that it doesn't get accidently freed while the decoder still needs it. For instance, an I or P picture can still be needed after displaying to decode interleaved B pictures.		{{fn\|vout_LinkPicture ( vout_thread_t p_vout, picture_t p_pic )\|Increases the refcount of the picture, so that it doesn't get accidently freed while the decoder still needs it. For instance, an I or P picture can still be needed after displaying to decode interleaved B pictures.}}
	vout_UnlinkPicture ( vout_thread_t p_vout, picture_t *p_pic )~~ :~~ Decreases the refcount of the picture. An unlink must be done for every link previously made.		{{fn\|vout_UnlinkPicture ( vout_thread_t p_vout, picture_t p_pic )\|Decreases the refcount of the picture. An unlink must be done for every link previously made.}}
	vout_DatePicture ( vout_thread_t p_vout, picture_t *p_pic )~~ :~~ Gives the picture a presentation date. You can start working on a picture before knowing precisely at what time it will be displayed. For instance to date an I or P picture, you must wait until you have decoded all previous B pictures (which are indeed placed after - decoding order != presentation order).		{{fn\|vout_DatePicture ( vout_thread_t p_vout, picture_t p_pic )\|Gives the picture a presentation date. You can start working on a picture before knowing precisely at what time it will be displayed. For instance to date an I or P picture, you must wait until you have decoded all previous B pictures (which are indeed placed after - decoding order != presentation order). }}
	vout_DisplayPicture ( vout_thread_t p_vout, picture_t *p_pic )~~ :~~ Tells the video output that a picture has been completely decoded and is ready to be rendered. It can be called before or after vout_DatePicture.		{{fn\|vout_DisplayPicture ( vout_thread_t p_vout, picture_t p_pic )\|Tells the video output that a picture has been completely decoded and is ready to be rendered. It can be called before or after vout_DatePicture. }}
	vout_DestroyPicture ( vout_thread_t p_vout, picture_t *p_pic )~~ :~~ Marks the picture as empty (useful in case of a stream parsing error).		{{fn\|vout_DestroyPicture ( vout_thread_t p_vout, picture_t p_pic )\|Marks the picture as empty (useful in case of a stream parsing error). }}
	subpicture_t vout_CreateSubPicture ( vout_thread_t *p_vout, int i_channel, int i_type )~~ :~~ Returns an allocated subpicture buffer. i_channel is the ID of the subpicture channel, i_type is DVD_SUBPICTURE or TEXT_SUBPICTURE, i_size is the length in bytes of the packet.		{{fn\|subpicture_t * vout_CreateSubPicture ( vout_thread_t *p_vout, int i_channel, int i_type )\|Returns an allocated subpicture buffer. i_channel is the ID of the subpicture channel, i_type is DVD_SUBPICTURE or TEXT_SUBPICTURE, i_size is the length in bytes of the packet. }}
	vout_DisplaySubPicture ( vout_thread_t p_vout, subpicture_t *p_subpic )~~ :~~ Tells the video output that a subpicture has been completely decoded. It obsoletes the previous subpicture.		{{fn\|vout_DisplaySubPicture ( vout_thread_t p_vout, subpicture_t p_subpic )\|Tells the video output that a subpicture has been completely decoded. It obsoletes the previous subpicture. }}
	vout_DestroySubPicture ( vout_thread_t p_vout, subpicture_t *p_subpic )~~ :~~ Marks the subpicture as empty.		{{fn\|vout_DestroySubPicture ( vout_thread_t p_vout, subpicture_t p_subpic )\|Marks the subpicture as empty.}}

	== How to write a video output plug-in ==		== How to write a video output plug-in ==
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	<br> Video outputs reside in the {{VLCSourceFolder\|modules/video_output}} directory. modules/video_output/x11/xcommon.c gives example of functions you must write :		<br> Video outputs reside in the {{VLCSourceFolder\|modules/video_output}} directory. modules/video_output/x11/xcommon.c gives example of functions you must write :

	int Activate ( vlc_object_t p_this )		{{fn\|int Activate ( vlc_object_t *p_this )}}
	**As for any VLC module, this function verifies if the module suits VLC core needs, by interrogating p_this structure.		* As for any VLC module, this function verifies if the module suits VLC core needs, by interrogating p_this structure.
	**In case of success, Activate sets up callback functions needed to run the video output (needed functions explained below), and returns VLC_SUCCESS		*In case of success, Activate sets up callback functions needed to run the video output (needed functions explained below), and returns VLC_SUCCESS
	**In case of failure, Activate frees memory and returns an error code (VLC_EGENERIC, VLC_ENOMEM, ...)		*In case of failure, Activate frees memory and returns an error code (VLC_EGENERIC, VLC_ENOMEM, ...)
	void Deactivate ( vlc_object_t p_this )		{{fn\|void Deactivate ( vlc_object_t *p_this )\|Called to destroy the module: Deactivate needs to free all allocated memory and destroys cleanly the video output thread}}
	**Called to destroy the module: Deactivate needs to free all allocated memory and destroys cleanly the video output thread

	The callback functions you need to implement are (callback name, function prototype) :		The callback functions you need to implement are (callback name, function prototype) :

	(p_vout->pf_init, static int InitVideo ( vout_thread_t );)		{{fn\|(p_vout->pf_init, static int InitVideo ( vout_thread_t * );)\|Called at the beginning of the output thread and each time the window is resized, it creates a buffer of output pictures }}
	**Called at the beginning of the output thread and each time the window is resized, it creates a buffer of output pictures		{{fn\|(p_vout->pf_end, static void EndVideo ( vout_thread_t * );)\|Destroys output pictures created by InitVideo }}
	(p_vout->pf_end, static void EndVideo ( vout_thread_t );)		{{fn\|(p_vout->pf_manage, static int ManageVideo ( vout_thread_t * );)\|Manage X11 events, and handle window resizing }}
	** Destroys output pictures created by InitVideo		{{fn\|(p_vout->pf_render, static void RenderVideo ( vout_thread_t , picture_t );)\|Optional (set p_vout->pf_render to NULL if not implemented); Used when pictures from the decoder need to be rendered before display }}
	(p_vout->pf_manage, static int ManageVideo ( vout_thread_t );)		{{fn\|(p_vout->pf_display, static void DisplayVideo ( vout_thread_t , picture_t );)\|Does the actual display of pictures onto screen }}
	**Manage X11 events, and handle window resizing		{{fn\|(p_vout->pf_control, static int Control ( vout_thread_t *, int, va_list );)\|Control facility for the video output}}
	(p_vout->pf_render, static void RenderVideo ( vout_thread_t , picture_t * );)
	**Optional (set p_vout->pf_render to NULL if not implemented); Used when pictures from the decoder need to be rendered before display
	(p_vout->pf_display, static void DisplayVideo ( vout_thread_t , picture_t * );)
	** Does the actual display of pictures onto screen
	(p_vout->pf_control, static int Control ( vout_thread_t , int, va_list );)
	**Control facility for the video output

	== How to write a YUV plug-in ==		== How to write a YUV plug-in ==

DoesItReallyMatter: +{{Back to|Hacker Guide}}

2019-04-17T06:39:47Z

+{{Back to|Hacker Guide}}

← Older revision		Revision as of 06:39, 17 April 2019
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			{{Back to\|Hacker Guide}}
	= The video output layer =		= The video output layer =

DoesItReallyMatter: Add links using Template:VLCSourceFile and Template:VLCSourceFolder

2019-02-15T09:41:39Z

Add links using Template:VLCSourceFile and Template:VLCSourceFolder

← Older revision		Revision as of 09:41, 15 February 2019
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	== Data structures and main loop ==		== Data structures and main loop ==

	Important data structures are defined under include/ in the files vlc_picture.h, vlc_subpicture.h and vlc_vout.h.		Important data structures are defined under {{VLCSourceFolder\|include}} in the files {{VLCSourceFile\|include/vlc_picture.h}}, {{VLCSourceFile\|include/vlc_subpicture.h}} and {{VLCSourceFile\|include/vlc_vout.h}}.

	=== picture_t ===		=== picture_t ===
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	=== subpicture_t and SPU ===		=== subpicture_t and SPU ===

	Note also the ''subpicture_t'' structure. In fact the VLC SPU (''SubPicture Unit'') decoder only parses the SPU header, and converts the SPU graphical data to an internal format which can be rendered much faster. So a part of the "actual" SPU decoder lies in src/video_output/vout_subpictures.c.		Note also the ''subpicture_t'' structure. In fact the VLC SPU (''SubPicture Unit'') decoder only parses the SPU header, and converts the SPU graphical data to an internal format which can be rendered much faster. So a part of the "actual" SPU decoder lies in {{VLCSourceFile\|src/video_output/vout_subpictures.c}}.

	=== vout_thread_t ===		=== vout_thread_t ===
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	A video output takes care of the system calls to display the pictures and manage the output window. For the most minimalistic framework, look at vmem.c, which just "renders" to dummy internal memory. From there, go on to directfb.c and svgalib.c, and finally go for x11 and windows.		A video output takes care of the system calls to display the pictures and manage the output window. For the most minimalistic framework, look at vmem.c, which just "renders" to dummy internal memory. From there, go on to directfb.c and svgalib.c, and finally go for x11 and windows.

	<br> Video outputs reside in the modules/video_output/ directory. modules/video_output/x11/xcommon.c gives example of functions you must write :		<br> Video outputs reside in the {{VLCSourceFolder\|modules/video_output}} directory. modules/video_output/x11/xcommon.c gives example of functions you must write :

	int Activate ( vlc_object_t p_this )		int Activate ( vlc_object_t p_this )

DoesItReallyMatter: Added the page to :Category:Pages to check, note was on the talk page

2019-01-21T11:38:27Z

Added the page to Category:Pages to check, note was on the talk page

← Older revision		Revision as of 11:38, 21 January 2019
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	{{Hacker_Guide}}		{{Hacker_Guide}}

			[[Category:Pages to check]]

Zil0: Update paths.

2017-08-01T12:03:34Z

Update paths.

← Older revision		Revision as of 12:03, 1 August 2017
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	== Data structures and main loop ==		== Data structures and main loop ==

	Important data structures are defined in include/~~video~~.h and ~~include/video_output~~.h.		Important data structures are defined under include/ in the files vlc_picture.h, vlc_subpicture.h and vlc_vout.h.

	=== picture_t ===		=== picture_t ===
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	=== subpicture_t and SPU ===		=== subpicture_t and SPU ===

	Note also the ''subpicture_t'' structure. In fact the VLC SPU (''SubPicture Unit'') decoder only parses the SPU header, and converts the SPU graphical data to an internal format which can be rendered much faster. So a part of the "actual" SPU decoder lies in src/video_output/~~video_spu~~.c.		Note also the ''subpicture_t'' structure. In fact the VLC SPU (''SubPicture Unit'') decoder only parses the SPU header, and converts the SPU graphical data to an internal format which can be rendered much faster. So a part of the "actual" SPU decoder lies in src/video_output/vout_subpictures.c.

	=== vout_thread_t ===		=== vout_thread_t ===

Corbax: /* How to write a YUV plug-in */

2013-11-14T17:27:37Z

How to write a YUV plug-in

← Older revision		Revision as of 17:27, 14 November 2013
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	Look at the C source plugins/yuv/transforms_yuv.c. You need to redefine just the same transformations. Basically, it is a matrix multiply operation. Good luck.		Look at the C source plugins/yuv/transforms_yuv.c. You need to redefine just the same transformations. Basically, it is a matrix multiply operation. Good luck.

	~~[[Category:Coding]]~~
	{{Hacker_Guide}}		{{Hacker_Guide}}

Corbax at 16:22, 30 October 2013

2013-10-30T16:22:42Z

← Older revision		Revision as of 16:22, 30 October 2013
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	[[Category:Coding]]		[[Category:Coding]]
	{{~~Documentation~~}}		{{Hacker_Guide}}

Corbax at 14:42, 1 October 2013

2013-10-01T14:42:04Z

← Older revision		Revision as of 14:42, 1 October 2013
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	Look at the C source plugins/yuv/transforms_yuv.c. You need to redefine just the same transformations. Basically, it is a matrix multiply operation. Good luck.		Look at the C source plugins/yuv/transforms_yuv.c. You need to redefine just the same transformations. Basically, it is a matrix multiply operation. Good luck.

			[[Category:Coding]]
			{{Documentation}}

J-b: moved Documentation:Hacker's Guide/Video Output to Hacker Guide/Video Output

2011-11-09T11:52:00Z

moved Documentation:Hacker's Guide/Video Output to Hacker Guide/Video Output

← Older revision	Revision as of 11:52, 9 November 2011
(No difference)

← Older revision		Revision as of 07:59, 17 April 2019
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	The video output exports a bunch of functions so that decoders can send their decoded data. The most important function is vout_CreatePicture which allocates the picture buffer to the size indicated by the video decoder. It then just needs to feed (void *) p_picture->p_data with the decoded data, and call vout_DisplayPicture and vout_DatePicture upon necessary.		The video output exports a bunch of functions so that decoders can send their decoded data. The most important function is vout_CreatePicture which allocates the picture buffer to the size indicated by the video decoder. It then just needs to feed (void *) p_picture->p_data with the decoded data, and call vout_DisplayPicture and vout_DatePicture upon necessary.

	picture_t vout_CreatePicture ( vout_thread_t *p_vout, int i_type, int i_width, int i_height )~~ :~~ Returns an allocated picture buffer. i_type will be for instance YUV_420_PICTURE, and i_width and i_height are in pixels.		{{fn\|picture_t * vout_CreatePicture ( vout_thread_t *p_vout, int i_type, int i_width, int i_height )\|Returns an allocated picture buffer. i_type will be for instance YUV_420_PICTURE, and i_width and i_height are in pixels.}}

	'''Warning'''		'''Warning'''
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	If no picture is available in the heap, vout_CreatePicture will return NULL.		If no picture is available in the heap, vout_CreatePicture will return NULL.

	vout_LinkPicture ( vout_thread_t p_vout, picture_t *p_pic )~~ :~~ Increases the refcount of the picture, so that it doesn't get accidently freed while the decoder still needs it. For instance, an I or P picture can still be needed after displaying to decode interleaved B pictures.		{{fn\|vout_LinkPicture ( vout_thread_t p_vout, picture_t p_pic )\|Increases the refcount of the picture, so that it doesn't get accidently freed while the decoder still needs it. For instance, an I or P picture can still be needed after displaying to decode interleaved B pictures.}}
	vout_UnlinkPicture ( vout_thread_t p_vout, picture_t *p_pic )~~ :~~ Decreases the refcount of the picture. An unlink must be done for every link previously made.		{{fn\|vout_UnlinkPicture ( vout_thread_t p_vout, picture_t p_pic )\|Decreases the refcount of the picture. An unlink must be done for every link previously made.}}
	vout_DatePicture ( vout_thread_t p_vout, picture_t *p_pic )~~ :~~ Gives the picture a presentation date. You can start working on a picture before knowing precisely at what time it will be displayed. For instance to date an I or P picture, you must wait until you have decoded all previous B pictures (which are indeed placed after - decoding order != presentation order).		{{fn\|vout_DatePicture ( vout_thread_t p_vout, picture_t p_pic )\|Gives the picture a presentation date. You can start working on a picture before knowing precisely at what time it will be displayed. For instance to date an I or P picture, you must wait until you have decoded all previous B pictures (which are indeed placed after - decoding order != presentation order). }}
	vout_DisplayPicture ( vout_thread_t p_vout, picture_t *p_pic )~~ :~~ Tells the video output that a picture has been completely decoded and is ready to be rendered. It can be called before or after vout_DatePicture.		{{fn\|vout_DisplayPicture ( vout_thread_t p_vout, picture_t p_pic )\|Tells the video output that a picture has been completely decoded and is ready to be rendered. It can be called before or after vout_DatePicture. }}
	vout_DestroyPicture ( vout_thread_t p_vout, picture_t *p_pic )~~ :~~ Marks the picture as empty (useful in case of a stream parsing error).		{{fn\|vout_DestroyPicture ( vout_thread_t p_vout, picture_t p_pic )\|Marks the picture as empty (useful in case of a stream parsing error). }}
	subpicture_t vout_CreateSubPicture ( vout_thread_t *p_vout, int i_channel, int i_type )~~ :~~ Returns an allocated subpicture buffer. i_channel is the ID of the subpicture channel, i_type is DVD_SUBPICTURE or TEXT_SUBPICTURE, i_size is the length in bytes of the packet.		{{fn\|subpicture_t * vout_CreateSubPicture ( vout_thread_t *p_vout, int i_channel, int i_type )\|Returns an allocated subpicture buffer. i_channel is the ID of the subpicture channel, i_type is DVD_SUBPICTURE or TEXT_SUBPICTURE, i_size is the length in bytes of the packet. }}
	vout_DisplaySubPicture ( vout_thread_t p_vout, subpicture_t *p_subpic )~~ :~~ Tells the video output that a subpicture has been completely decoded. It obsoletes the previous subpicture.		{{fn\|vout_DisplaySubPicture ( vout_thread_t p_vout, subpicture_t p_subpic )\|Tells the video output that a subpicture has been completely decoded. It obsoletes the previous subpicture. }}
	vout_DestroySubPicture ( vout_thread_t p_vout, subpicture_t *p_subpic )~~ :~~ Marks the subpicture as empty.		{{fn\|vout_DestroySubPicture ( vout_thread_t p_vout, subpicture_t p_subpic )\|Marks the subpicture as empty.}}

	== How to write a video output plug-in ==		== How to write a video output plug-in ==
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	<br> Video outputs reside in the {{VLCSourceFolder\|modules/video_output}} directory. modules/video_output/x11/xcommon.c gives example of functions you must write :		<br> Video outputs reside in the {{VLCSourceFolder\|modules/video_output}} directory. modules/video_output/x11/xcommon.c gives example of functions you must write :

	int Activate ( vlc_object_t p_this )		{{fn\|int Activate ( vlc_object_t *p_this )}}
	**As for any VLC module, this function verifies if the module suits VLC core needs, by interrogating p_this structure.		* As for any VLC module, this function verifies if the module suits VLC core needs, by interrogating p_this structure.
	**In case of success, Activate sets up callback functions needed to run the video output (needed functions explained below), and returns VLC_SUCCESS		*In case of success, Activate sets up callback functions needed to run the video output (needed functions explained below), and returns VLC_SUCCESS
	**In case of failure, Activate frees memory and returns an error code (VLC_EGENERIC, VLC_ENOMEM, ...)		*In case of failure, Activate frees memory and returns an error code (VLC_EGENERIC, VLC_ENOMEM, ...)
	void Deactivate ( vlc_object_t p_this )		{{fn\|void Deactivate ( vlc_object_t *p_this )\|Called to destroy the module: Deactivate needs to free all allocated memory and destroys cleanly the video output thread}}
	**Called to destroy the module: Deactivate needs to free all allocated memory and destroys cleanly the video output thread

	The callback functions you need to implement are (callback name, function prototype) :		The callback functions you need to implement are (callback name, function prototype) :

	(p_vout->pf_init, static int InitVideo ( vout_thread_t );)		{{fn\|(p_vout->pf_init, static int InitVideo ( vout_thread_t * );)\|Called at the beginning of the output thread and each time the window is resized, it creates a buffer of output pictures }}
	**Called at the beginning of the output thread and each time the window is resized, it creates a buffer of output pictures		{{fn\|(p_vout->pf_end, static void EndVideo ( vout_thread_t * );)\|Destroys output pictures created by InitVideo }}
	(p_vout->pf_end, static void EndVideo ( vout_thread_t );)		{{fn\|(p_vout->pf_manage, static int ManageVideo ( vout_thread_t * );)\|Manage X11 events, and handle window resizing }}
	** Destroys output pictures created by InitVideo		{{fn\|(p_vout->pf_render, static void RenderVideo ( vout_thread_t , picture_t );)\|Optional (set p_vout->pf_render to NULL if not implemented); Used when pictures from the decoder need to be rendered before display }}
	(p_vout->pf_manage, static int ManageVideo ( vout_thread_t );)		{{fn\|(p_vout->pf_display, static void DisplayVideo ( vout_thread_t , picture_t );)\|Does the actual display of pictures onto screen }}
	**Manage X11 events, and handle window resizing		{{fn\|(p_vout->pf_control, static int Control ( vout_thread_t *, int, va_list );)\|Control facility for the video output}}
	(p_vout->pf_render, static void RenderVideo ( vout_thread_t , picture_t * );)
	**Optional (set p_vout->pf_render to NULL if not implemented); Used when pictures from the decoder need to be rendered before display
	(p_vout->pf_display, static void DisplayVideo ( vout_thread_t , picture_t * );)
	** Does the actual display of pictures onto screen
	(p_vout->pf_control, static int Control ( vout_thread_t , int, va_list );)
	**Control facility for the video output

	== How to write a YUV plug-in ==		== How to write a YUV plug-in ==