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diff --git a/doc/hackersguide/output.docbook b/doc/hackersguide/output.docbook new file mode 100644 index 000000000..dc254641d --- /dev/null +++ b/doc/hackersguide/output.docbook @@ -0,0 +1,668 @@ +<chapter id="output"> + <title>xine's output layer</title> + + <sect1> + <title>Post plugin layer</title> + <para> + In this section you will learn, how the powerful post plugin architecture + works and how to write post plugins. + </para> + <sect2> + <title>General principle of post plugins</title> + <para> + The name "post plugin" comes from "postprocessing" which already describes + what these plugins are supposed to do: they take video frames, audio + buffers or subpicture planes as they leave the decoders and apply arbitrary + processing to them. Then they pass processed elements on to the output + loops. Post plugins can not only be chained to process the predecessor's + output and advance the data to their successor, they can form arbitrary trees, + since post plugins can have any number of inputs and outputs. Additionally, + the interconnection of the plugins currently inserted in such a tree can + be changed on the fly during playback. The public function + <function>xine_post_wire()</function> is used by frontends to form such + connections. + </para> + <para> + Due to the variety of possible applications, the interface post plugins have + to implement is just the basic foundation. The complexity comes from hooking + your post plugin into the engine data paths for video frames and audio buffers, + intercepting the data and performing your operation on them. This is done by + taking the interface of a video or audio port, replacing some of the functions + with your own ones and passing the interface to the decoder or predecessor + post plugin that is going to feed you with data by accessing this interface + and by doing that, calling the functions you provide. From there you can do + almost anything you want. Constructing video frames from audio buffers to + visualize sound is possible as well as just outputting an integer giving the + average brightness of an image. It is also possible to invent post plugins + with no output (not very useful, unless the plugin has some side-effect) or + no input at all; for the latter you have to create your own pthread, otherwise + your plugin will not do anything. An audio signal generator could be + implemented like this. The various data types, post plugins can + accept as input or offer as output are defined in <filename>xine.h</filename> + as <varname>XINE_POST_DATA_*</varname> defines. + </para> + <para> + Some terminology used in the following explanations: + <itemizedlist> + <listitem> + <para> + <varname>down direction</varname>: + The direction from the decoders to the output. This is the way video or audio + data (actual content and meta information) usually travels through the engine. + </para> + </listitem> + <listitem> + <para> + <varname>up direction</varname>: + The direction from the output to the decoders. This is the way some video or audio + metadata like metronom timestamps travel through the engine. + </para> + </listitem> + <listitem> + <para> + <varname>interception</varname>: + Post plugins are inserted into the engine data paths by the means of the decorator + design pattern. This works by taking engine structures with member funtions like + video or audio ports, video frames or overlay managers and inserting your own functions + into a copy of this structure. This is called interception. This modified structure + is then passed up to the plugin that uses it and thus calls your replaced functions. + </para> + </listitem> + </itemizedlist> + </para> + </sect2> + <sect2> + <title>Writing a xine post plugin</title> + <para> + The post plugin API is declared in <filename>src/xine-engine/post.h</filename> + The plugin info of post plugins contains the post plugin type, which is one of the + <varname>XINE_POST_TYPE_*</varname> defines and the init_class function of the plugin. + </para> + <para> + <programlisting> post_plugin_t *open_plugin(post_class_t *class_gen, int inputs, xine_audio_port_t **audio_target, xine_video_port_t **video_target);</programlisting> + Returns an instance of the plugin. Some post plugins evaluate <varname>inputs</varname> + to open a variable number of inputs. Since almost all post plugins have audio or video + outputs, you can hand in a NULL-terminated array of ports to connect to these outputs. + In this function you can also intercept these ports so that your plugin is actually used. + There is a helper function to initialize a <type>post_plugin_t</type>, which you are + encouraged to use: <function>_x_post_init()</function>. + </para> + <para> + <programlisting> char *get_identifier(post_class_t *class_gen);</programlisting> + This function returns a short identifier describing the plugin. + </para> + <para> + <programlisting> char *get_description(post_class_t *class_gen);</programlisting> + This function returns a plaintext, one-line string describing the plugin. + </para> + <para> + <programlisting> void dispose(post_class_t *class_gen);</programlisting> + This function frees the memory used by the video out plugin class object. + </para> + <para> + The <type>post_plugin_t</type> structure contains the publicly visible + part of the post plugin with the audio and video inputs and the type of + the post plugin. Not publicly visible are the lists of all inputs and outputs, + the <function>dispose()</function> function and some internal stuff which + plugins do not have to worry about. + </para> + <para> + <programlisting> void dispose(post_plugin_t *this_gen);</programlisting> + This function frees the memory used by the plugin instance, but not necessarily + immediately. Since post plugins enter their own functions into engine structures, + they might still be needed when <function>dispose()</function> is being called. + They maintain a usage counter to detect that. To check for such a condition, you + should use the <function>_x_post_dispose()</function> helper function like that: + <programlisting> + if (_x_post_dispose(this)) + really_free(this);</programlisting> + <function>_x_post_dispose()</function> frees any ressources allocated by any of the + post plugin helper functions and returns boolean true, if the plugin is not needed + any more. + </para> + </sect2> + <sect2> + <title>Interception</title> + <para> + Currently, we have four engine structures which can be intercepted by post plugins: + video ports, video frames, overlay managers and audio ports. You could do this + interception manually, but since this is quite a complex process, there are helper + functions to assist you and their usage is encouraged. + </para> + <sect3> + <title>Intercepting a video port</title> + <para> + <programlisting> + post_video_port_t *_x_post_intercept_video_port(post_plugin_t *post, + xine_video_port_t *port, post_in_t **input, post_out_t **output);</programlisting> + This function will intercept <varname>port</varname> and returns a structure + for you to pass up. All functions in the port will be replaced with dummy + pass through functions that do nothing but relaying the call down to the original + port. If you want (that is, <varname>input</varname> or <varname>output</varname> are + not NULL), this function will also create the input and output descriptors complete + with rewiring functions and add them to the relevant lists. + This is required, if you want this port to be advertised by the plugin to the outside world. + </para> + <para> + <type>post_video_port_t</type> makes a variety of interception schemes very easy. + If you want to replace any of the default functions with your own, just enter it + into <varname>new_port</varname>. You can use <varname>original_port</varname> + from within your function to propagate calls down to the original port. + The constraint is that your functions have to ensure that every original + port held open scores one usage counter point, so that opened ports are always + closed before the plugin is disposed. Therefore, you should use the macro + <function>_x_post_inc_usage()</function> before calling + <function>original_port->open()</function> and use the macro + <function>_x_post_dec_usage()</function> after calling + <function>original_port->close()</function>. Note that <function>_x_post_dec_usage()</function> + might dispose the plugin, when <function>dispose()</function> has been called + earlier and usage count drops to zero, so do never touch plugin structures after + <function>_x_post_dec_usage()</function>. In addition, you must never call a port + function of the original port when the port is not open. + </para> + <para> + Intercepting video frames or the overlay manager of the port is even easier. + You do not have to reimplement <function>get_frame()</function> or + <function>get_overlay_manager()</function>. Just enter a <varname>intercept_frame</varname> + or <varname>intercept_ovl</varname> function which returns boolean true, if + you want to intercept. The functions to insert in the intercepted frame or overlay + manager are taken from <varname>new_frame</varname> and <varname>new_manager</varname> + respectively. Note that the defaults are reversed: If you do not enter such a + decision function for either one, all frames and no overlay manager will be intercepted. + </para> + <para> + For convenience <type>post_video_port_t</type> also contains pointers to the + current stream and to the current post plugin and a user_data pointer, where you + can put in anything you need in addition. If your port is used by more than one + thread, you can also enforce locking on the port, frame or overlay manager level + by entering a lock into <varname>port_lock</varname>, <varname>frame_lock</varname> or + <varname>manager_lock</varname> respectively. + </para> + </sect3> + <sect3> + <title>Intercepting an audio port</title> + <para> + Audio port interception is just a stripped down version of video port interception. + Everything related to frames and overlay manager is not needed and audio buffers + do not need to be intercepted, since they have no member functions. Everything else + of the above still applies. + </para> + </sect3> + <sect3> + <title>Intercepting overlay manager</title> + <para> + <programlisting> void _x_post_intercept_overlay_manager(video_overlay_manager_t *original, post_video_port_t *port);</programlisting> + Interception of the overlay manager is done automatically when your + <function>intercept_ovl()</function> decision function returns boolean true. + Should you ever decide not to use that, interception can be done with this helper + function, which simply creates an intercepted overlay manager with dummy + pass through functions in <varname>port->new_manager</varname> and stores the original + manager in <varname>port->original_manager</varname>. + </para> + <para> + No matter how you intercepted the overlay manager, your own replacement + functions will receive <varname>port->new_manager</varname> as the overlay manager + argument. But you most likely want to have access to the <type>post_video_port_t</type> + from within your functions. For that, there exists a pointer retrieval function: + <programlisting> post_video_port_t *_x_post_ovl_manager_to_port(video_overlay_manager_t *manager);</programlisting> + </para> + </sect3> + <sect3> + <title>Intercepting a video frame</title> + <para> + <programlisting> + vo_frame_t *_x_post_intercept_video_frame(vo_frame_t *frame, post_video_port_t *port); + vo_frame_t *_x_post_restore_video_frame(vo_frame_t *frame, post_video_port_t *port);</programlisting> + Interception of video frames is done automatically when your + <function>intercept_frame()</function> decision function returns boolean true or + when there is no such function in <type>post_video_port_t</type>. + Should you ever decide not to use that, interception can be done with the helper + function <function>_x_post_intercept_video_frame()</function>. + </para> + <para> + Since the same video frame can be in use in the decoder and in the output and in + any post plugin in between at the same time, simply modifying the frame + structure does not work, because every user of the frame needs to see his version + and the frame must always travel along the same path through the plugins for its + entire lifetime. To ensure that, <function>_x_post_intercept_video_frame()</function> + provides a shallow copy of the frame structure with the original frame attached to + <varname>copy->next</varname>. This copy will be filled with your own + frame functions from <varname>port->new_frame</varname> and with dummy pass + through functions for those you did not provide. This way, every part of xine + using this frame will see its own frame structure with a list of frame + contexts from down the data path attached to <varname>frame->next</varname>. + <function>_x_post_restore_video_frame()</function> reverses this and should be + used when the frame is freed or disposed. + </para> + <para> + Your own replacement functions will receive the copied frame as as argument. + But you most likely want to have access to the <type>post_video_port_t</type> + from within your functions. For that, there exists a pointer retrieval function: + <programlisting> post_video_port_t *_x_post_video_frame_to_port(vo_frame_t *frame);</programlisting> + The constraint is that your functions have to ensure that every intercepted + frame scores one usage counter point, so that these frames are always + freed or disposed before the plugin is disposed. Therefore, you should use the macro + <function>_x_post_inc_usage()</function> before calling + <function>_x_post_intercept_video_frame()</function> and use the macro + <function>_x_post_dec_usage()</function> after calling + <function>_x_post_restore_video_frame()</function>. Note that <function>_x_post_dec_usage()</function> + might dispose the plugin, when <function>dispose()</function> has been called + earlier and usage count drops to zero, so do never touch plugin structures after + <function>_x_post_dec_usage()</function>. + </para> + <para> + From within your own frame functions, you can propagate calls to the original + frame by calling a function on <varname>frame->next</varname>. Since + modifications to the frame can travel both upwards and downwards (decoders and + output can modify the frame), changes need to be copied between the frame + structure contexts. You should use the <function>_x_post_frame_copy_down()</function> + and <function>_x_post_frame_copy_up()</function> helper functions like that: + <programlisting> + _x_post_frame_copy_down(frame, frame->next); + frame->next->draw(frame->next, stream); + _x_post_frame_copy_up(frame, frame->next);</programlisting> + </para> + <para> + If your post plugin modifies the content of the frame, you have to modify + a deep copy of the frame, because the decoder might still use the frame as + a reference frame for future decoding. The usual procedure is: + <programlisting> + modified_frame = port->original_port->get_frame(port->original_port, …); + _x_post_frame_copy_down(frame, modified_frame); + copy_and_modify(frame, modified_frame); + skip = modified_frame->draw(modified_frame, stream); + _x_post_frame_copy_up(frame, modified_frame); + modified_frame->free(modified_frame);</programlisting> + </para> + <para> + When the output receives a frame via <function>draw()</function>, + it usually receives the stream where the frame + originates as well and modifies the state of this stream by passing + the frame through the stream's metronom. Sometimes this is unwanted. + For example, when you pass the same frame to the output more than once, it + will confuse metronom. To solve this, you can call + <function>frame->next->draw()</function> with NULL as the stream. + You might also want to prevent frames from being passed down to the output + completely, because your post plugin creates something else from these frames, + but does not need them to be drawn. In both these situations, you have + to call the helper function <function>_x_post_frame_u_turn()</function> + when the frame is drawn, because this does some housekeeping which the + decoder might expect to take place. + </para> + <para> + The following diagram summarizes the situations of a video frame passing + through a post plugin: + </para> + <mediaobject> + <imageobject> + <imagedata fileref="post_frame.png" format="PNG" /> + </imageobject> + <imageobject> + <imagedata fileref="post_frame.eps" format="EPS" /> + </imageobject> + <caption> + <para>video frame passing through a post plugin</para> + </caption> + </mediaobject> + </sect3> + <sect3> + <title>Summary of constraints</title> + <itemizedlist> + <listitem> + <para> + Call <function>_x_post_inc_usage()</function> before port <function>open()</function> + before any other port function. + </para> + </listitem> + <listitem> + <para> + Call <function>_x_post_inc_usage()</function> before issueing an intercepted frame. + </para> + </listitem> + <listitem> + <para> + Call <function>_x_post_dec_usage()</function> after port <function>close()</function> + and do not call any port functions after that. + </para> + </listitem> + <listitem> + <para> + Call <function>_x_post_dec_usage()</function> after restoring a frame. + </para> + </listitem> + <listitem> + <para> + When a frame is drawn by your plugin, it must either be drawn on the original + port with the correct stream as argument or U-turned (or passed through a + private metronom manually). + </para> + </listitem> + <listitem> + <para> + If your post plugin keeps locked frames, release them when your input port is being + closed. + </para> + </listitem> + <listitem> + <para> + Do not assume your plugin is alive after <function>_x_post_dec_usage()</function>. + </para> + </listitem> + </itemizedlist> + </sect3> + </sect2> + <sect2> + <title>Rewiring and the ticket system</title> + <para> + Rewiring is the reconnection of one post plugin's outputs and another post plugin's + inputs. This can happen on the fly during playback, which makes this a very delicate + process. In one such input to output connection, only the output is active by either + writing data directly to the connected input or by calling functions there. Therefore + we have to notify only the output, when it is rewired. This is done by calling the + <function>rewire()</function> member function of the corresponding + <type>xine_post_out_t</type> when the frontend issues a rewiring on this output. + This is done from the frontend thread for the rewire operation to return synchroneously. + But since this can happen on the fly, we have to assure that no other thread is relying + on the connection while we modify it. For this, threads working within post plugins + have to be accounted and on demand suspended in safe positions. For this, xine offers + a synchronization facility called "tickets". + </para> + <sect3> + <title>Ticket system principles and operations</title> + <para> + The idea of the ticket system is based on an extended read-write lock, where there can + be many readers in parallel, but only one exclusive writer. A certain interface might + require you to have a ticket before calling its functions. The ticket system now + allows multiple threads to operate within the component behind the interface by + granting as many tickets as needed. But should an outside operation require exclusive + access to the component, all granted tickets can be revoked and have to be given back + by the threads who hold them, which suspends the threads. After the exclusive + operation, tickets will be reissued so all suspended threads can continue where they + stopped. We will now look at the ticket primitives in detail: + </para> + <variablelist> + <varlistentry> + <term><function>acquire()</function></term> + <listitem> + <para> + You receive a new ticket. If the ticket is currently revoked, you can be blocked + until it is reissued. There is one exception to this: You can acquire a revoked + ticket, if you revoked it atomic yourself. You can also acquire a ticket irrevocably. + Between acquire and release of an irrevocable ticket, it is guaranteed that + you will not be blocked by ticket revocation. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><function>release()</function></term> + <listitem> + <para> + You give a ticket back when you do not need it any longer. If the ticket is + currently revoked, you can be blocked until it is reissued. If you acquired the + ticket irrevocably, you have to release it irrevocably as well. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><function>renew()</function></term> + <listitem> + <para> + You must only call this function, when the ticket has been revoked, so be + sure to check <varname>ticket_revoked</varname> before. You give the ticket + back and receive a new one. In between, you can be blocked until the ticket is + reissued. You have to renew irrevocably, if you cannot assure that the thread holds + no irrevocable tickets. If you can assure this, renew revocably. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><function>revoke()</function></term> + <listitem> + <para> + This function can only be called by the xine engine, plugins do not have access to it. + It revokes all tickets and after finite time, all threads will run into a + <function>acquire()</function>, <function>release()</function> or <function>renew()</function> + and will be suspended there. Then the revocation returns and you can modify structures + or call functions with the knowledge that all ticket holders will remain in safe + positions. When you additionally need exclusive access where no other revoker + can interfere, you have to revoke atomic. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><function>issue()</function></term> + <listitem> + <para> + This function can only be called by the xine engine, plugins do not have access to it. + It ends ticket revocation and hands out new tickets to all threads that applied with a + <function>acquire()</function> or <function>renew()</function>. If you revoked the + tickets atomic, you have to issue them atomic. + </para> + </listitem> + </varlistentry> + </variablelist> + <para> + When you use the ticket system in any way, you have to obey to the following rules: + <itemizedlist> + <listitem> + <para> + Assure to release irrevocable tickets ater a finite time. + </para> + </listitem> + <listitem> + <para> + Assure to release or renew revocable tickets ater a finite time. + </para> + </listitem> + <listitem> + <para> + Assure to reissue tickets you revoked atomic after a finite time. + </para> + </listitem> + <listitem> + <para> + Pair calls properly. + </para> + </listitem> + <listitem> + <para> + Never revoke a ticket you hold. + </para> + </listitem> + <listitem> + <para> + Never acquire a ticket you revoked atomic before. + </para> + </listitem> + <listitem> + <para> + Never acquire a ticket revocable more than once. + </para> + </listitem> + </itemizedlist> + </para> + </sect3> + <sect3> + <title>Ticket handling in decoder and post plugins</title> + <para> + The contract of the video and audio port interfaces is that you need to have + the port ticket, when you want to call functions of these interfaces. The decoder + plugins do not have to worry about this at all, since the decoder loops inside the + engine handle the ticketing. Post plugins get the ticket assigned by the engine, + but usually, a post plugin does not create a new thread, it is called by the + decoder thread and therefore already owns the necessary ticket. All port functions + are also ticket-safe as they follow all the rules given above. + </para> + <para> + You only have to remember that tickets need to be renewed as soon as possible, + when the are revoked. For this, the helper function + <function>_x_post_rewire()</function> should be used in prominent locations + where it is safe to be suspended. Candidates for such locations are at the + beginning of the port's <function>open()</function> and + <function>get_frame()</function>/<function>get_buffer()</function> functions. + The default pass through implementations for intercepted ports already do this. + </para> + <para> + The port tickets are revoked, whenever a rewiring takes place or the engine + switches into pause mode. The tickets are reissued, when the rewiring is finished + or the engine switches from pause mode into playback. Some post plugins might + contain critical parts, where they must not be interrupted by a rewire or pause. + These sections can be enclosed in <function>_x_post_lock()</function> and + <function>_x_post_unlock()</function>, which will simply acquire and release an + irrevocable ticket for you. As long as you hold such a ticket, it is guaranteed + that you will never be interrupted by a pause or rewire. + </para> + </sect3> + </sect2> + </sect1> + + <sect1> + <title>Video output</title> + <para> + In order to allow for device-dependant acceleration features, xine + calls upon the video output plugin for more than just displaying + images. The tasks performed by the video plugins are: + <itemizedlist> + <listitem> + <para> + Allocation of <type>vo_frame_t</type> structures and their + subsequent destruction. + </para> + </listitem> + <listitem> + <para> + Allocation of memory for use by one frame (this is to allow + for the ability of some video output plugins to map frames directly + into video-card memory hence removing the need for the frame to + be copied across the PCI/AGP bus at display time). + </para> + </listitem> + <listitem> + <para> + Most important, the ability to render/copy a given + frame to the output device. + </para> + </listitem> + <listitem> + <para> + Optionally the copying of the frame from a file dependant + colour-space and depth into the frame structure. This is to allow for + on-the fly colour-space conversion and scaling if required (e.g. the XShm + ouput plugin uses this mechanism). + </para> + </listitem> + </itemizedlist> + </para> + <para> + Although these extra responsibilities add great complexity to your + plugin it should be noted that they allow plugins to take full advantage + of any special hardware-acceleration without sacrificing flexibility. + </para> + <sect2> + <title>Writing a xine video out plugin</title> + <para> + The video out plugin API is declared in <filename>src/xine-engine/video_out.h</filename> + The plugin info of video out plugins contains the visual type, priority, + and the init_class function of the plugin. + </para> + <para> + The <varname>visual_type</varname> field is used by xine to + determine if the GUI used by the client is supported by the plugin + (e.g. X11 output plugins require the GUI to be running under the + X Windowing system) and also to determine the type of information passed to the + <function>open_plugin()</function> function as its <varname>visual</varname> parameter. + </para> + <para> + <programlisting> char *get_description(video_driver_class_t *this_gen);</programlisting> + This function returns a plaintext, one-line string describing the plugin. + </para> + <para> + <programlisting> char *get_identifier(video_driver_class_t *this_gen);</programlisting> + This function returns a shorter identifier describing the plugin. + </para> + <para> + <programlisting> void dispose(video_driver_class_t *this_gen);</programlisting> + This function frees the memory used by the video out plugin class object. + </para> + <para> + <programlisting> vo_driver_t *get_instance(video_driver_class_t *class_gen, const void *visual);</programlisting> + Returns an instance of the plugin. + The <varname>visual</varname> is a pointer to a visual-dependant + structure/variable. For example, if you had previously claimed your + plugin was of the VISUAL_TYPE_X11 type, this would be a pointer + to a <type>x11_visual_t</type>, which amongst other things hold the + <type>Display</type> variable associated with the + X-server xine should display to. See plugin source-code for other + VISUAL_TYPE_* constants and associated structures. Note that this + field is provided by the client application and so if you wish to add another visual + type you will either need to extend an existing client or write a new + one. + </para> + <para> + <programlisting> uint32_t get_capabilities(vo_driver_t *this_gen);</programlisting> + Returns a bit mask describing the output plugin's capabilities. + You may logically OR the <varname>VO_CAP_*</varname> constants together to get + a suitable bit-mask (via the '|' operator). + </para> + <para> + <programlisting> + int get_property(vo_driver_t *self, int property); + int set_property(vo_driver_t *self, int property, int value); + void get_property_min_max(vo_driver_t *self, int property, int *min, int *max);</programlisting> + Handle the getting, setting of properties and define their bounds. + Valid property IDs can be found in the <filename>video_out.h</filename> + header file. + </para> + <para> + <programlisting> int gui_data_exchange(vo_driver_t *self, int data_type, void *data);</programlisting> + Accepts various forms of data from the UI (e.g. the mouse has moved or the + window has been hidden). Look at existing plugins for examples of data + exchanges from various UIs. + </para> + <para> + <programlisting> vo_frame_t *alloc_frame(vo_driver_t *self);</programlisting> + Returns a pointer to a xine video frame. + Typically the video plugin will add private fields to the end of the + <type>vo_frame_t</type> structure which are used for internal purposes by the plugin. + </para> + <para> + The function pointers within the frame structure provide a mechanism for the + driver to retain full control of how the frames are managed and rendered to. If + the VO_CAP_COPIES_IMAGE flag was set in the plugins capabilities then the + copy field is required and will be called sequentially for each 16-pixel high + strip in the image. The plugin may then decide, based on the frame's format, how + this is copied into the frame. + </para> + <para> + <programlisting> void update_frame_format(vo_driver_t *self, vo_frame_t *img, uint32_t width, uint32_t height, double ratio, int format, int flags);</programlisting> + This function will be called each time the colour-depth/space or size of a frame changes. + Typically this function would allocate sufficient memory for the frame, assign the pointers + to the individual planes of the frame to the <varname>base</varname> field of the + frame and perform any driver-specific changes. + </para> + <para> + <programlisting> void display_frame(vo_driver_t *self, vo_frame_t *vo_img);</programlisting> + Renders a given frame to the output device. + </para> + <para> + <programlisting> + void overlay_begin(vo_driver_t *self, vo_frame_t *vo_img, int changed); + void overlay_blend(vo_driver_t *self, vo_frame_t *vo_img, vo_overlay_t *overlay); + void overlay_end(vo_driver_t *self, vo_frame_t *vo_img);</programlisting> + These are used to blend overlays on frames. <function>overlay_begin()</function> is called, + when the overlay appears for the first time, <function>overlay_blend()</function> is then + called for every subsequent frame and <function>overlay_end()</function> is called, when + the overlay should disappear again. + </para> + <para> + <programlisting> int redraw_needed(vo_driver_t *self);</programlisting> + Queries the driver, if the current frame needs to be drawn again. + </para> + <para> + <programlisting> void dispose(vo_driver_t *self);</programlisting> + Releases all resources and frees the plugin. + </para> + </sect2> + </sect1> + +</chapter> |