Hacker Guide/Core - Revision history

DoesItReallyMatter: /* VLC Pipeline and Modularity */ nn

2019-05-30T21:33:49Z

VLC Pipeline and Modularity: nn

← Older revision		Revision as of 21:33, 30 May 2019
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	One of the main concepts in VLC is "'''''modularity'''''".		One of the main concepts in VLC is "'''''modularity'''''".

	VLC is, in fact, a complete [~~http~~:~~//en.wikipedia.org/wiki/Multimedia_framework~~ multimedia framework] (like DirectShow or GStreamer) where you can load and plug-in many modules dynamically, depending on the necessity.		VLC is, in fact, a complete [[wikipedia:multimedia framework\|multimedia framework]] (like DirectShow or GStreamer) where you can load and plug-in many modules dynamically, depending on the necessity.

	The core framework is used to do the "wiring" and the media processing, from input (files, network streams) to output (audio or video, on a screen or a network). It uses modules to do most of the work at every stage (various muxers, demuxers, decoders, filters and outputs).<br> Even the interfaces are plugins for libVLC.		The core framework is used to do the "wiring" and the media processing, from input (files, network streams) to output (audio or video, on a screen or a network). It uses modules to do most of the work at every stage (various muxers, demuxers, decoders, filters and outputs).<br> Even the interfaces are plugins for libVLC.

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

2019-04-17T03:46:43Z

+{{Back to|Hacker Guide}}

← Older revision		Revision as of 03:46, 17 April 2019
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			{{Back to\|Hacker Guide}}
	== Introduction to libVLCcore ==		== Introduction to libVLCcore ==

DoesItReallyMatter: /* Core Source code details */ Add git link

2019-03-04T08:02:39Z

Core Source code details: Add git link

← Older revision		Revision as of 08:02, 4 March 2019
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	== Core Source code details ==		== Core Source code details ==

	All the [[libVLCcore]] source files are located in the src/ directory and its subdirectories:		All the [[libVLCcore]] source files are located in the {{VLCSourceFolder\|src}} directory and its subdirectories:

	; [[{{#rel2abs:../Audio Output}}\|<code>audio_output/</code>]]		; [[{{#rel2abs:../Audio Output}}\|<code>audio_output/</code>]]

DoesItReallyMatter: rel2abs

2019-02-15T21:08:11Z

rel2abs

← Older revision		Revision as of 21:08, 15 February 2019
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	Every module offers different features that will best suit a particular use-case or a particular environment.<br>		Every module offers different features that will best suit a particular use-case or a particular environment.<br>
	Besides, most portability of VLC results from writing [[~~Hacker Guide~~/Audio_Output\|audio_output]]/[[~~Hacker Guide~~/Video Output\|video_output]]/[[~~Hacker Guide~~/Interfaces\|interface]] modules specific to the platform.		Besides, most portability of VLC results from writing [[{{#rel2abs:../Audio_Output}}\|audio_output]]/[[{{#rel2abs:../Video Output}}\|video_output]]/[[{{#rel2abs:../Interfaces}}\|interface]] modules specific to the platform.

	'''plugins''' modules are loaded and unloaded dynamically by functions in {{VLCSourceFile\|src/modules/modules.c}} .<br>		'''plugins''' modules are loaded and unloaded dynamically by functions in {{VLCSourceFile\|src/modules/modules.c}} .<br>
	Modules can also be built directly into the application which uses libVLC, for instance when VLC is on an operating system that does not have support for dynamically loadable code. They are then called '''builtins'''.		Modules can also be built directly into the application which uses libVLC, for instance when VLC is on an operating system that does not have support for dynamically loadable code. They are then called '''builtins'''.

	In the [[~~Hacker Guide~~/VLC source tree\|source code]], modules are usually located inside the [[~~Hacker Guide~~/Modules source tree\|modules/ subdirectory]].		In the [[{{#rel2abs:../VLC source tree}}\|source code]], modules are usually located inside the [[{{#rel2abs:../Modules source tree}}\|modules/ subdirectory]].

	== Thread management ==		== Thread management ==
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	All the [[libVLCcore]] source files are located in the src/ directory and its subdirectories:		All the [[libVLCcore]] source files are located in the src/ directory and its subdirectories:

	; [[~~Hacker Guide~~/Audio Output\|<code>audio_output/</code>]]		; [[{{#rel2abs:../Audio Output}}\|<code>audio_output/</code>]]
	: Initializes the audio mixer, ie. finds the right playing frequency, and then resamples audio frames received from the decoder(s).		: Initializes the audio mixer, ie. finds the right playing frequency, and then resamples audio frames received from the decoder(s).
	; <code>config/</code>		; <code>config/</code>
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	; <code>extras/</code>		; <code>extras/</code>
	: Mostly platform-specific code		: Mostly platform-specific code
	; [[~~Hacker Guide~~/Input\|<code>input/</code>]]		; [[{{#rel2abs:../Input}}\|<code>input/</code>]]
	: Opens an input module, reads packets, parses them and passes reconstituted elementary streams to the decoder(s).		: Opens an input module, reads packets, parses them and passes reconstituted elementary streams to the decoder(s).
	; [[~~Hacker Guide~~/Interfaces\|<code>interface/</code>]]		; [[{{#rel2abs:../Interfaces}}\|<code>interface/</code>]]
	: Contains code for user interaction such as key presses and device ejection.		: Contains code for user interaction such as key presses and device ejection.
	; <code>misc/</code>		; <code>misc/</code>
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	; <code>text/</code>		; <code>text/</code>
	: Charset stuff		: Charset stuff
	; [[~~Hacker Guide~~/Video Output\|<code>video_output/</code>]]		; [[{{#rel2abs:../Video Output}}\|<code>video_output/</code>]]
	: Initializes the video display, gets all pictures and subpictures (ie. subtitles) from the decoder(s), optionally converts them to another format (such as YUV to RGB), and displays them.		: Initializes the video display, gets all pictures and subpictures (ie. subtitles) from the decoder(s), optionally converts them to another format (such as YUV to RGB), and displays them.

	{{Hacker_Guide}}		{{Hacker_Guide}}

DoesItReallyMatter: /* The modules in VLC */ Change wikilink target: Hacker Guide/Modules source tree → Hacker Guide/VLC source tree

2019-02-15T07:50:46Z

The modules in VLC: Change wikilink target: Hacker Guide/Modules source tree → Hacker Guide/VLC source tree

← Older revision		Revision as of 07:50, 15 February 2019
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	Modules can also be built directly into the application which uses libVLC, for instance when VLC is on an operating system that does not have support for dynamically loadable code. They are then called '''builtins'''.		Modules can also be built directly into the application which uses libVLC, for instance when VLC is on an operating system that does not have support for dynamically loadable code. They are then called '''builtins'''.

	In the [[Hacker Guide/~~Modules~~ source tree\|source code]], modules are usually located inside the [[Hacker Guide/Modules source tree\|modules/ subdirectory]].		In the [[Hacker Guide/VLC source tree\|source code]], modules are usually located inside the [[Hacker Guide/Modules source tree\|modules/ subdirectory]].

	== Thread management ==		== Thread management ==

DoesItReallyMatter: Simplify wikilinks, replace deprecated tags, correct spelling, page variable, bypass old page-name redirects, link via Template:VLCSourceFile

2019-02-15T07:46:00Z

Simplify wikilinks, replace deprecated tags, correct spelling, page variable, bypass old page-name redirects, link via Template:VLCSourceFile

Show changes

EPirat: /* Core Source code details */ Improved formatting

2017-01-23T18:52:27Z

Core Source code details: Improved formatting

← Older revision		Revision as of 18:52, 23 January 2017
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	All the [[LibVLCcore\|libVLCcore]] source files are located in the src/ directory and its subdirectories:		All the [[LibVLCcore\|libVLCcore]] source files are located in the src/ directory and its subdirectories:

	*[[Documentation:Hacker's Guide/Audio Output\|audio_output/]]: ~~initializes~~ the audio mixer, ie. finds the right playing frequency, and then resamples audio frames received from the decoder(s).		; [[Documentation:Hacker's Guide/Audio Output\|<tt>audio_output/</tt>]]
	*config/: ~~load~~ the configuration from command line and configuration file, provides functions for the modules to read and write to configuration		: Initializes the audio mixer, ie. finds the right playing frequency, and then resamples audio frames received from the decoder(s).
	*control/: ~~functions~~ to control the behaviour of [[LibVLCcore\|libVLCcore]], like Play/Pause, volume management, fullscreen, log verbosity, etc.		; <tt>config/</tt>
	*extras/: ~~mostly~~ platform-specific code		: Load the configuration from command line and configuration file, provides functions for the modules to read and write to configuration
	*[[Documentation:Hacker's Guide/Input\|input/]]: ~~opens~~ an input module, reads packets, parses them and passes reconstituted elementary streams to the decoder(s).		; <tt>control/</tt>
	*[[Documentation:Hacker's Guide/Interfaces\|interface/]]: ~~contains~~ code for user interaction such as key presses and device ejection.		: Functions to control the behaviour of [[LibVLCcore\|libVLCcore]], like Play/Pause, volume management, fullscreen, log verbosity, etc.
	*misc/: ~~miscellaneous~~ utilities used in other parts of libvlc, such as the thread system, the message queue, CPU detection, the object lookup system, or platform-specific code.		; <tt>extras/</tt>
	*modules/: ~~modules~~ management		: Mostly platform-specific code
	*network/: ~~network~~ interface (socket management, network errors, etc.)		; [[Documentation:Hacker's Guide/Input\|<tt>input/</tt>]]
	*osd/: On Screen Display manipulation		: Opens an input module, reads packets, parses them and passes reconstituted elementary streams to the decoder(s).
	*playlist/: ~~manages~~ playlist interaction such as stop, play, next, or random playback.		; [[Documentation:Hacker's Guide/Interfaces\|<tt>interface/</tt>]]
	*stream_output/: ~~functions~~ to stream audio and video to the network		: Contains code for user interaction such as key presses and device ejection.
	*test/: libVLC needs to be tested, and not only by users~~ ~~:)		; <tt>misc/</tt>
	*text/: ~~charset~~ stuff		: Miscellaneous utilities used in other parts of libvlc, such as the thread system, the message queue, CPU detection, the object lookup system, or platform-specific code.
	*[[Documentation:Hacker's Guide/Video Output\|video_output/]]: ~~initializes~~ the video display, gets all pictures and subpictures (ie. subtitles) from the decoder(s), optionally converts them to another format (such as YUV to RGB), and displays them.		; <tt>modules/</tt>
			: Modules management
			; <tt>network/</tt>
			: Network interface (socket management, network errors, etc.)
			; <tt>osd/</tt>
			: On Screen Display manipulation
			; <tt>playlist/</tt>
			: Manages playlist interaction such as stop, play, next, or random playback.
			; <tt>stream_output/</tt>
			: Functions to stream audio and video to the network
			; <tt>test/</tt>
			: libVLC needs to be tested, and not only by users :)
			; <tt>text/</tt>
			: Charset stuff
			; [[Documentation:Hacker's Guide/Video Output\|<tt>video_output/</tt>]]
			: Initializes the video display, gets all pictures and subpictures (ie. subtitles) from the decoder(s), optionally converts them to another format (such as YUV to RGB), and displays them.

	{{Hacker_Guide}}		{{Hacker_Guide}}

EPirat: /* Synchronization */ Improve formatting

2017-01-23T18:44:54Z

Synchronization: Improve formatting

← Older revision		Revision as of 18:44, 23 January 2017
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	Having several input and video_output threads reading multiple files at the same time is permitted, despite the fact that the current interface doesn't allow any way to do it (this is subject to change in the near future). Anyway the client has been written from the ground up with this in mind. This also implies that a non-reentrant library (including in particular liba52<sup>[[Talk:Hacker Guide/Core\|See talk page]]</sup>) cannot be used without using a global lock.		Having several input and video_output threads reading multiple files at the same time is permitted, despite the fact that the current interface doesn't allow any way to do it (this is subject to change in the near future). Anyway the client has been written from the ground up with this in mind. This also implies that a non-reentrant library (including in particular liba52<sup>[[Talk:Hacker Guide/Core\|See talk page]]</sup>) cannot be used without using a global lock.

	Presentation Time Stamps located in the system layer of the stream are passed to the decoders, and all resulting samples are dated accordingly. The output layers are supposed to play them at the right time. Dates are converted to microseconds~~ ;~~ an absolute date is the number of microseconds since Epoch (Jan 1st, 1970). The mtime_t type is a signed 64-bit integer.		Presentation Time Stamps located in the system layer of the stream are passed to the decoders, and all resulting samples are dated accordingly. The output layers are supposed to play them at the right time. Dates are converted to microseconds, an absolute date is the number of microseconds since Epoch (Jan 1st, 1970). The <code>mtime_t</code> type is a signed 64-bit integer.

	The current date can be retrieved with mdate(). The execution of a thread can be suspended until a certain date via mwait ( mtime_t date ). You can sleep for a fixed number of microseconds with msleep ( mtime_t delay ).		The current date can be retrieved with <code>mdate()</code>. The execution of a thread can be suspended until a certain date via <code>mwait ( mtime_t date )</code>. You can sleep for a fixed number of microseconds with <code>msleep ( mtime_t delay )</code>.

	=== Warning ===		=== Warning ===

	Please remember to wake up slightly before the presentation date, if some particular treatment needs to be done (e.g. a chroma transformation). For instance in modules/codec/libmpeg2.c, track of the average decoding times is kept to ensure pictures are not decoded too late.		Please remember to wake up slightly before the presentation date, if some particular treatment needs to be done (e.g. a chroma transformation). For instance in <tt>modules/codec/libmpeg2.c</tt>, track of the average decoding times is kept to ensure pictures are not decoded too late.

	== Core Source code details ==		== Core Source code details ==

EPirat: /* Thread management */ Improve formatting

2017-01-23T18:42:33Z

Thread management: Improve formatting

← Older revision		Revision as of 18:42, 23 January 2017
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	Multi-process approach wasn't chosen either, because multi-process decoders usually imply more overhead (problems of shared memory) and communication between processes is harder.		Multi-process approach wasn't chosen either, because multi-process decoders usually imply more overhead (problems of shared memory) and communication between processes is harder.

	VLC's threading structure is modeled after POSIX threads (''pthread''). However, for portability reasons, VLC does not use pthread_* functions directly, but a similar custom set of APIs.		VLC's threading structure is modeled after POSIX threads (''pthread''). However, for portability reasons, VLC does not use <code>pthread_*</code> functions directly, but a similar custom set of APIs.

	=== Threads (vlc_thread_t) ===		=== Threads (vlc_thread_t) ===
	* vlc_clone() ~~creates~~ a thread.		; <code>vlc_clone()</code>
	* vlc_join() ~~waits~~ for a thread to terminate and releases its resources		: Creates a thread.
			; <code>vlc_join()</code>
			: Waits for a thread to terminate and releases its resources

	=== Mutual exclusion (vlc_mutex_t) ===		=== Mutual exclusion (vlc_mutex_t) ===
	* vlc_mutex_init() ~~creates~~ a non-recursive mutex.		; <code>vlc_mutex_init()</code>
	* vlc_mutex_init_recursive() ~~creates~~ a recursive mutex (discouraged).		: Creates a non-recursive mutex.
	* vlc_mutex_lock() ~~locks~~ a mutex, waiting if required.		; <code>vlc_mutex_init_recursive()</code>
	* vlc_mutex_trylock() ~~locks~~ a mutex if it is not already locked, or returns an error otherwise.		: Creates a recursive mutex (discouraged).
	* vlc_mutex_unlock() ~~unlocks~~ a mutex.		; <code>vlc_mutex_lock()</code>
	* vlc_mutex_destroy() ~~destroys~~ a mutex.		: Locks a mutex, waiting if required.
			; <code>vlc_mutex_trylock()</code>
			: Locks a mutex if it is not already locked, or returns an error otherwise.
			; <code>vlc_mutex_unlock()</code>
			: Unlocks a mutex.
			; <code>vlc_mutex_destroy()</code>
			: Destroys a mutex.

	=== Condition variable (vlc_cond_t) ===		=== Condition variable (vlc_cond_t) ===
	* vlc_cond_init() ~~creates~~ a condition variable using the monotonic clock (''mdate()'') for timeouts.		; <code>vlc_cond_init()</code>
	* vlc_cond_init_daytime() ~~creates~~ a condition variable using the realtime clock / wall clock for timeouts.		: Creates a condition variable using the monotonic clock (<code>mdate()</code>) for timeouts.
	* vlc_cond_signal() ~~signals~~ one thread waiting on a condition variable.		; <code>vlc_cond_init_daytime()</code>
	* vlc_cond_broadcast() ~~signals~~ all threads waiting on a condition variable.		: Creates a condition variable using the realtime clock / wall clock for timeouts.
	* vlc_cond_wait() ~~waits~~ for a condition variable to be signaled (can also wake up spuriously).		; <code>vlc_cond_signal()</code>
	* vlc_cond_timedwait() ~~waits~~ for a condition variable to be signaled up to a certain timeout (can also wake up spuriosuly).		: Signals one thread waiting on a condition variable.
	* vlc_cond_destroy() ~~destroys~~ a condition variable.		; <code>vlc_cond_broadcast()</code>
			: Signals all threads waiting on a condition variable.
			; <code>vlc_cond_wait()</code>
			: Waits for a condition variable to be signaled (can also wake up spuriously).
			; <code>vlc_cond_timedwait()</code>
			: Waits for a condition variable to be signaled up to a certain timeout (can also wake up spuriosuly).
			; <code>vlc_cond_destroy()</code>
			: Destroys a condition variable.

	=== Misc ===		=== Misc ===
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	=== Atomic variables ===		=== Atomic variables ===
	Atomic variables are small (sizeof(void *)) values that can be manipulated from multiple threads without locking. See include/vlc_atomic.h for the list of supported operations.		Atomic variables are small <code>(sizeof(void *))</code> values that can be manipulated from multiple threads without locking. See <tt>include/vlc_atomic.h</tt> for the list of supported operations.

	== Synchronization ==		== Synchronization ==

Duffsterlp: Remove duplicate 'modules' text

2016-01-05T01:31:58Z

Remove duplicate 'modules' text

← Older revision		Revision as of 01:31, 5 January 2016
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	*control/: functions to control the behaviour of [[LibVLCcore\|libVLCcore]], like Play/Pause, volume management, fullscreen, log verbosity, etc.		*control/: functions to control the behaviour of [[LibVLCcore\|libVLCcore]], like Play/Pause, volume management, fullscreen, log verbosity, etc.
	*extras/: mostly platform-specific code		*extras/: mostly platform-specific code
	[[Documentation:Hacker's Guide/Input\|input/]]: opens an input module, reads packets, parses them and passes reconstituted elementary streams to the decoder(s).modules/: module management		*[[Documentation:Hacker's Guide/Input\|input/]]: opens an input module, reads packets, parses them and passes reconstituted elementary streams to the decoder(s).
	*[[Documentation:Hacker's Guide/Interfaces\|interface/]]: contains code for user interaction such as key presses and device ejection.		*[[Documentation:Hacker's Guide/Interfaces\|interface/]]: contains code for user interaction such as key presses and device ejection.
	*misc/: miscellaneous utilities used in other parts of libvlc, such as the thread system, the message queue, CPU detection, the object lookup system, or platform-specific code.		*misc/: miscellaneous utilities used in other parts of libvlc, such as the thread system, the message queue, CPU detection, the object lookup system, or platform-specific code.