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diff --git a/doc/hackersguide/internals.docbook b/doc/hackersguide/internals.docbook new file mode 100644 index 000000000..d31a6eff5 --- /dev/null +++ b/doc/hackersguide/internals.docbook @@ -0,0 +1,762 @@ +<chapter id="internals"> + <title>xine internals</title> + + <sect1> + <title>Engine architecture and data flow</title> + <mediaobject> + <imageobject> + <imagedata fileref="architecture.png" format="PNG" /> + </imageobject> + <imageobject> + <imagedata fileref="architecture.eps" format="EPS" /> + </imageobject> + <caption> + <para>xine engine architecture</para> + </caption> + </mediaobject> + <para> + Media streams usually consist of audio and video data multiplexed + into one bitstream in the so-called system-layer (e.g. AVI, Quicktime or MPEG). + A demuxer plugin is used to parse the system layer and extract audio and video + packages. The demuxer uses an input plugin to read the data and stores it + in pre-allocated buffers from the global buffer pool. + The buffers are then added to the audio or video stream fifo. + </para> + <para> + From the other end of these fifos the audio and video decoder threads + consume the buffers and hand them over to the current audio or video + decoder plugin for decompression. These plugins then send the decoded + data to the output layer. The buffer holding the encoded + data is no longer needed and thus released to the global buffer pool. + </para> + <para> + In the output layer, the video frames and audio samples pass through a + post plugin tree, which can apply effects or other operations to the data. + When reaching the output loops, frames and samples are enqueued to be + displayed, when the presentation time has arrived. + </para> + <para> + A set of extra information travels with the data. Starting at the input and + demuxer level, where this information is generated, the data is attached to + the buffers as they wait in the fifo. The decoder loops copy the data to + a storage of their own. From there, every frame and audio buffer leaving + the stream layer is tagged with the data the decoder loop storage currently + holds. + </para> + </sect1> + + <sect1> + <title>Plugin system</title> + <para> + The plugin system enables some of xine's most valuable features: + <itemizedlist> + <listitem> + <para> + drop-in extensiability + </para> + </listitem> + <listitem> + <para> + support parallel installation of multiple (incompatible) libxine versions + </para> + </listitem> + <listitem> + <para> + support for multiple plugin directories + (<filename>$prefix/lib/xine/plugins</filename>, + <filename>$HOME/.xine/plugins</filename>, …) + </para> + </listitem> + <listitem> + <para> + support for recursive plugin directories + (plugins are found even in subdirectories of the plugin directories) + </para> + </listitem> + <listitem> + <para> + version management + (On start, xine finds all plugins in its plugin (sub)directories and + chooses an appropriate version (usually the newest) for each plugin.) + </para> + </listitem> + <listitem> + <para> + simplification + (Plugins don't have to follow any special naming convention, + and any plugin may contain an arbitrary subset of input, demuxer, + decoder or output plugins.) + </para> + </listitem> + </itemizedlist> + </para> + <para> + Essentally, plugins are just shared objects, ie dynamic libraries. In + contrast to normal dynamic libraries, they are stored outside of the + system's library PATHs and libxine does its own bookkeeping, which + enables most advanced features mentioned above. + </para> + <sect2> + <title>Plugin location and filesystem layout</title> + <para> + The primary goal for this new plugin mechanism was the need to support + simultaneous installation of several (most likely incompatible) + libxine versions without them overwriting each other's + plugins. Therefore, we have this simple layout: + </para> + <para> + Plugins are installed below XINE_PLUGINDIR + (<filename>/usr/local/lib/xine/plugins</filename> by default). + Note that plugins are never directly installed into XINE_PLUGINDIR. + Instead, a separate subdirectory is created for each "plugin + provider". A plugin provider is equivalent with the exact version of + one source package. Typical examples include "xine-lib-0.9.11" or + "xine-vcdnav-1.0". Every source package is free to install an + arbitrary number of plugins in its own, private directory. If a + package installs several plugins, they may optionally be organized + further into subdirectories. + </para> + <para> + So you will finally end up with something like this: + <screen> + /usr/local/lib/xine/plugins + xine-lib-0.9.11 + demux_mpeg_block.so + decode_mpeg.so + video_out_xv.so + … + xine-vcdnav-0.9.11 + input_vcdnav.so + xine-lib-1.2 + input + file.so + stdin_fifo.so + vcd.so + demuxers + fli.so + avi.so + … + decoders + ffmpeg.so + mpeg.so (may contain mpeg 1/2 audio and video decoders) + pcm.so + … + output + video_xv.so + audio_oss.so + … + xine-lib-3.0 + avi.so (avi demuxer) + mpeg.so (contains mpeg demuxers and audio/video decoders) + video_out_xv.so (Xv video out) + …</screen> + </para> + <para> + As you can see, every package is free to organize plugins at will + below its own plugin provider directory. + Additionally, administrators may choose to put plugins directly into + XINE_PLUGINDIR, or in a "local" subdirectory. + Users may wish to put additional plugins in ~/.xine/plugins/. + Again, there may be subdirectories to help organize the plugins. + </para> + <para> + The default value for XINE_PLUGINDIR can be obtained using the + <command>pkg-config --variable=plugindir libxine</command> command. + </para> + </sect2> + <sect2> + <title>Plugin Content: What's inside the .so?</title> + <para> + Each plugin library (.so file) contains an arbitrary number of (virtual) + plugins. Typically, it will contain exactly one plugin. However, it + may be useful to put a set of related plugins in one library, so they + can share common code. + </para> + <para> + First of all, what is a virtual plugin? + A virtual plugin is essentially a structure that is defined by the + xine engine. This structure typically contains lots of function + pointers to the actual API functions. + For each plugin API, there are several API versions, and each API + version may specify a new, incompatible structure. Therefore, it is + essential that only those plugins are loaded that support current + libxine's API, so the .so file needs a plugin list that + provides libxine with the version information, even before it tries to + load any of the plugins. + </para> + <para> + This plugin list is held in an array named <varname>xine_plugin_info</varname>": + <programlisting> + plugin_info_t xine_plugin_info[] = { + /* type, API, "name", version, special_info, init_function */ + { PLUGIN_DEMUX, 20, "flac", XINE_VERSION_CODE, NULL, demux_flac_init_class }, + { PLUGIN_AUDIO_DECODER, 13, "flacdec", XINE_VERSION_CODE, &dec_info_audio, init_plugin }, + { PLUGIN_NONE, 0, "", 0, NULL, NULL } + };</programlisting> + </para> + <para> + The structure of xine_plugin_info may <emphasis>never</emphasis> be changed. + If it ever needs to be changed, it must be renamed to avoid + erraneous loading of incompatible plugins. + </para> + <para> + <varname>xine_plugin_info</varname> can contain any number of plugins + and must be terminated with a <type>PLUGIN_NONE</type> entry. Available plugin + types are: + <programlisting> + #define PLUGIN_NONE 0 + #define PLUGIN_INPUT 1 + #define PLUGIN_DEMUX 2 + #define PLUGIN_AUDIO_DECODER 3 + #define PLUGIN_VIDEO_DECODER 4 + #define PLUGIN_SPU_DECODER 5 + #define PLUGIN_AUDIO_OUT 6 + #define PLUGIN_VIDEO_OUT 7 + #define PLUGIN_POST 8</programlisting> + </para> + <para> + The plugin version number is generated from xine-lib's version number + like this: MAJOR * 10000 + MINOR * 100 + SUBMINOR. + This is not required, but it's an easy way to ensure that the version + increases for every release. + </para> + <para> + Every entry in <varname>xine_plugin_info</varname> has an initialization + function for the plugin class context. + This function returns a pointer to freshly allocated (typically + via <function>malloc()</function>) structure containing mainly function + pointers; these are the "methods" of the plugin class. + </para> + <para> + The "plugin class" is not what we call to do the job yet (like decoding + a video or something), it must be instantiated. One reason for having the + class is to hold any global settings that must be accessed by every + instance. Remember that xine library is multistream capable: multible + videos can be decoded at the same time, thus several instances of the + same plugin are possible. + </para> + <para> + If you think this is pretty much an object-oriented aproach, + then you're right. + </para> + <para> + A fictitious file input plugin that supports input plugin API 12 and + 13, found in xine-lib 2.13.7 would then define this plugin list: + <programlisting> + #include <xine/plugin.h> + … + plugin_t *init_api12(void) { + input_plugin_t *this; + + this = malloc(sizeof(input_plugin_t)); + … + return (plugin_t *)this; + } + /* same thing, with different initialization for API 13 */ + + const plugin_info_t xine_plugin_info[] = { + { PLUGIN_INPUT, 12, "file", 21307, init_api12 }, + { PLUGIN_INPUT, 13, "file", 21307, init_api13 }, + { PLUGIN_NONE, 0, "", 0, NULL } + }</programlisting> + This input plugin supports two APIs, other plugins might provide a + mixture of demuxer and decoder plugins that belong together somehow + (ie. share common code). + </para> + <para> + You'll find exact definitions of public functions and plugin structs + in the appropriate header files for each plugin type: + <filename>input/input_plugin.h</filename> for input plugins, + <filename>demuxers/demux.h</filename> for demuxer plugins, + <filename>xine-engine/video_decoder.h</filename> for video decoder plugins, + <filename>xine-engine/audio_decoder.h</filename> for audio decoder plugins, + <filename>xine-engine/post.h</filename> for post plugins, + <filename>xine-engine/video_out.h</filename> for video out plugins, + <filename>xine-engine/audio_out.h</filename> for audio out plugins. + Additional information will also be given in the dedicated sections below. + </para> + <para> + Many plugins will need some additional "private" data fields. + These should be simply added at the end of the plugin structure. + For example a demuxer plugin called "foo" with two private + fields "xine" and "count" may have a plugin structure declared in + the following way: + <programlisting> + typedef struct { + /* public fields "inherited" from demux.h */ + demux_plugin_t demux_plugin; + + xine_t *xine; + int count; + } demux_foo_t;</programlisting> + </para> + <para> + The plugin would then access public members via the + <varname>demux_plugin</varname> field and private fields directly. + </para> + <para> + Summary: Plugins consist of two C-style classes, each representing a different context. + <itemizedlist> + <listitem> + <para> + The first is the so called "plugin class" context. This is a singleton context, + which means it will exist either not at all or at most once per xine context. + This plugin class context is a C-style class which is subclassing the related + class from the xine plugin headers. This contains functions, which are + independent of the actual instance of the plugin. Most prominently, it contains + a factory method to instantiate the next context. + </para> + </listitem> + <listitem> + <para> + The second context is the instance context. This is another C-style class, which + is constructed and disposed withing the plugin class context. This one does + the actual work and subclasses the related plugin struct from the xine plugin + headers. It is instantiated for every separate running instance of the plugin + </para> + </listitem> + </itemizedlist> + </para> + </sect2> + </sect1> + + <sect1> + <title>What is this metronom thingy?</title> + <para> + Metronom serves two purposes: + <itemizedlist> + <listitem> + <para> + Generate vpts (virtual presentation time stamps) from pts (presentation time stamps) + for a/v output and synchronization. + </para> + </listitem> + <listitem> + <para> + Provide a master clock (system clock reference, scr), possibly provided + by external scr plugins (this can be used if some hardware decoder or network + server dictates the time). + </para> + </listitem> + </itemizedlist> + </para> + <para> + pts/vpts values are given in 1/90000 sec units. pts values in mpeg streams + may wrap (that is, return to zero or any other value without further notice), + can be missing on some frames or (for broken streams) may "dance" around + the correct values. Metronom therefore has some heuristics built-in to generate + clean vpts values which can then be used in the output layers to schedule audio/video + output. + </para> + <para> + The heuristics used in metronom have always been a field of research. Current metronom's + implementation <emphasis>tries</emphasis> to stick to pts values as reported from demuxers, + that is, vpts may be obtained by a simple operation of vpts = pts + <varname>vpts_offset</varname>, + where <varname>vpts_offset</varname> takes into account any wraps. Whenever pts is zero, + metronom will estimate vpts based on previous values. If a difference is found between the + estimated and calculated vpts values by above formula, it will be smoothed by using a + "drift correction". + </para> + </sect1> + + <sect1> + <title>How does xine synchronize audio and video?</title> + <para> + Every image frame or audio buffer leaving decoder is tagged by metronom with + a vpts information. This will tell video_out and audio_out threads when that + data should be presented. Usually there isn't a significative delay associated + with video driver, so we expect it to get on screen at the time it's + delivered for drawing. Unfortunately the same isn't true for audio: all sound + systems implement some amount of buffering (or fifo), any data being send to it + <emphasis>now</emphasis> will only get played some time in future. audio_out thread + must take this into account for making perfect A-V sync by asking the sound latency + to audio driver. + </para> + <para> + Some audio drivers can't tell the current delay introduced in playback. This is + especially true for most sound servers like ESD or aRts and explain why in such + cases the sync is far from perfect. + </para> + <para> + Another problem xine must handle is the sound card clock drift. vpts are + compared to the system clock (or even to a different clock provided by a scr plugin) + for presentation but sound card is sampling audio by its own clocking + mechanism, so a small drift may occur. As the playback goes on this + error will accumulate possibly resulting in audio gaps or audio drops. To avoid that + annoying effect, two countermeasures are available (switchable with xine config + option <parameter>audio.synchronization.av_sync_method</parameter>): + <itemizedlist> + <listitem> + <para> + The small sound card errors are feedbacked to metronom. The details + are given by <filename>audio_out.c</filename> comments: + <programlisting> + /* By adding gap errors (difference between reported and expected + * sound card clock) into metronom's vpts_offset we can use its + * smoothing algorithms to correct sound card clock drifts. + * obs: previously this error was added to xine scr. + * + * audio buf ---> metronom --> audio fifo --> (buf->vpts - hw_vpts) + * (vpts_offset + error) gap + * <---------- control --------------| + * + * Unfortunately audio fifo adds a large delay to our closed loop. + * + * These are designed to avoid updating the metronom too fast. + * - it will only be updated 1 time per second (so it has a chance of + * distributing the error for several frames). + * - it will only be updated 2 times for the whole audio fifo size + * length (so the control will wait to see the feedback effect) + * - each update will be of gap/SYNC_GAP_RATE. + * + * Sound card clock correction can only provide smooth playback for + * errors < 1% nominal rate. For bigger errors (bad streams) audio + * buffers may be dropped or gaps filled with silence. + */</programlisting> + </para> + </listitem> + <listitem> + <para> + The audio is stretched or squeezed a slight bit by resampling, thus compensating + the drift: The next comment in <filename>audio_out.c</filename> explains: + <programlisting> + /* Alternative for metronom feedback: fix sound card clock drift + * by resampling all audio data, so that the sound card keeps in + * sync with the system clock. This may help, if one uses a DXR3/H+ + * decoder board. Those have their own clock (which serves as xine's + * master clock) and can only operate at fixed frame rates (if you + * want smooth playback). Resampling then avoids A/V sync problems, + * gaps filled with 0-frames and jerky video playback due to different + * clock speeds of the sound card and DXR3/H+. + */</programlisting> + </para> + </listitem> + </itemizedlist> + </para> + </sect1> + + <sect1 id="osd"> + <title>Overlays and OSD</title> + <para> + The roots of xine overlay capabilities are DVD subpictures and subtitles support + (also known as 'spu'). The DVD subtitles are encoded in a RLE (Run Length Encoding - the + most simple compressing technique) format, with a palette of colors and transparency + levels. You probably thought that subtitles were just simple text saved into DVDs, right? + Wrong, they are bitmaps. + </para> + <para> + In order to optimize to the most common case, xine's internal format for screen overlays + is a similar representation to the 'spu' data. This brings not only performance + benefit (since blending functions may skip large image areas due to RLE) but also + compatibility: it's possible to re-encode any xine overlay to the original spu format + for displaying with mpeg hardware decoders like DXR3. + </para> + <para> + Displaying subtitles requires the ability to sync them to the video stream. This + is done using the same kind of pts/vpts stuff of a-v sync code. DVD subtitles, + for example, may request: show this spu at pts1 and hide it at pts2. This brings the + concept of the 'video overlay manager', that is a event-driven module for managing + overlay's showing and hiding. + </para> + <para> + The drawback of using internal RLE format is the difficulty in manipulating it + as graphic. To overcome that we created the 'OSD renderer', where OSD stands + for On Screen Display just like in TV sets. The osd renderer is a module + providing simple graphic primitives (lines, rectagles, draw text etc) over + a "virtual" bitmap area. Everytime we want to show that bitmap it will + be RLE encoded and sent to the overlay manager for displaying. + </para> + <mediaobject> + <imageobject> + <imagedata fileref="overlays.png" format="PNG" /> + </imageobject> + <imageobject> + <imagedata fileref="overlays.eps" format="EPS" /> + </imageobject> + <caption> + <para>overlays architecture</para> + </caption> + </mediaobject> + <sect2> + <title>Overlay Manager</title> + <para> + The overlay manager interface is available to any xine plugin. It's a bit unlikely + to be used directly, anyway here's a code snippet for enqueueing an overlay for + displaying: + <programlisting> + video_overlay_event_t event; + + event.object.handle = this->video_overlay->get_handle(this->video_overlay,0); + + memset(this->event.object.overlay, 0, sizeof(*this->event.object.overlay)); + + /* set position and size for this overlay */ + event.object.overlay->x = 0; + event.object.overlay->y = 0; + event.object.overlay->width = 100; + event.object.overlay->height = 100; + + /* clipping region is mostly used by dvd menus for highlighting buttons */ + event.object.overlay->clip_top = 0; + event.object.overlay->clip_bottom = image_height; + event.object.overlay->clip_left = 0; + event.object.overlay->clip_right = image_width; + + /* the hard part: provide a RLE image */ + event.object.overlay->rle = your_rle; + event.object.overlay->data_size = your_size; + event.object.overlay->num_rle = your_rle_count; + + /* palette must contain YUV values for each color index */ + memcpy(event.object.overlay->clip_color, color, sizeof(color)); + + /* this table contains transparency levels for each color index. + 0 = completely transparent, 15 - completely opaque */ + memcpy(event.object.overlay->clip_trans, trans, sizeof(trans)); + + /* set the event type and time for displaying */ + event.event_type = EVENT_SHOW_SPU; + event.vpts = 0; /* zero is a special vpts value, it means 'now' */ + video_overlay->add_event(video_overlay, &event);</programlisting> + </para> + </sect2> + <sect2> + <title>OSD Renderer</title> + <para> + OSD is a general API for rendering stuff over playing video. It's available both + to xine plugins and to frontends. + </para> + <para> + The first thing you need is to allocate a OSD object for drawing from the + renderer. The code below allocates a 300x200 area. This size can't be changed + during the lifetime of a OSD object, but it's possible to place it anywhere + over the image. + </para> + <programlisting> + osd_object_t osd; + + osd = this->osd_renderer->new_object(osd_renderer, 300, 200);</programlisting> + <para> + Now we may want to set font and color for text rendering. Although we will + refer to fonts over this document, in fact the OSD can be any kind of bitmap. Font + files are searched and loaded during initialization from + <filename>$prefix/share/xine/fonts/</filename> and <filename>~/.xine/fonts</filename>. + There's a sample utility to convert truetype fonts at + <filename>xine-lib/misc/xine-fontconv.c</filename>. Palette may be manipulated directly, + however most of the time it's convenient to use pre-defined text palettes. + </para> + <programlisting> + /* set sans serif 24 font */ + osd_renderer->set_font(osd, "sans", 24); + + /* copy pre-defined colors for white, black border, transparent background to + starting at the index used by the first text palette */ + osd_renderer->set_text_palette(osd, TEXTPALETTE_WHITE_BLACK_TRANSPARENT, OSD_TEXT1); + + /* copy pre-defined colors for white, no border, translucid background to + starting at the index used by the second text palette */ + osd_renderer->set_text_palette(osd, TEXTPALETTE_WHITE_NONE_TRANSLUCID, OSD_TEXT2);</programlisting> + <para> + Now render the text and show it: + <programlisting> + osd_renderer->render_text(osd, 0, 0, "white text, black border", OSD_TEXT1); + osd_renderer->render_text(osd, 0, 30, "white text, no border", OSD_TEXT2); + + osd_renderer->show(osd, 0); /* 0 stands for 'now' */</programlisting> + </para> + <para> + There's a 1:1 mapping between OSD objects and overlays, therefore the + second time you send an OSD object for displaying it will actually substitute + the first image. By using set_position() function we can move overlay + over the video. + </para> + <programlisting> + for( i=0; i < 100; i+=10 ) { + osd_renderer->set_position(osd, i, i ); + osd_renderer->show(osd, 0); + sleep(1); + } + osd_renderer->hide(osd, 0);</programlisting> + <para> + For additional functions please check osd.h or the public header. + </para> + <sect3> + <title>OSD palette notes</title> + <para> + The palette functions demand some additional explanation, skip this if you + just want to write text fast without worring with details! :) + </para> + <para> + We have a 256-entry palette, each one defining yuv and transparency levels. + Although xine fonts are bitmaps and may use any index they want, we have + defined a small convention: + </para> + <programlisting> + /* + Palette entries as used by osd fonts: + + 0: not used by font, always transparent + 1: font background, usually transparent, may be used to implement + translucid boxes where the font will be printed. + 2-5: transition between background and border (usually only alpha + value changes). + 6: font border. if the font is to be displayed without border this + will probably be adjusted to font background or near. + 7-9: transition between border and foreground + 10: font color (foreground) + */</programlisting> + <para> + The so called 'transitions' are used to implement font anti-aliasing. That + convention requires that any font file must use only the colors from 1 to 10. + When we use the set_text_palette() function we are just copying 11 palette + entries to the specified base index. + </para> + <para> + That base index is the same we pass to render_text() function to use the + text palette. With this scheme is possible to have several diferent text + colors at the same time and also draw fonts over custom background. + </para> + <programlisting> + /* obtains size the text will occupy */ + renderer->get_text_size(osd, text, &width, &height); + + /* draws a box using font background color (translucid) */ + renderer->filled_rect(osd, x1, y1, x1+width, y1+height, OSD_TEXT2 + 1); + + /* render text */ + renderer->render_text(osd, x1, y1, text, OSD_TEXT2);</programlisting> + </sect3> + <sect3> + <title>OSD text and palette FAQ</title> + <para> + Q: What is the format of the color palette entries? + </para> + <para> + A: It's the same as used by overlay blending code (YUV). + </para> + <para> + Q: What is the relation between a text palette and a palette + I set with xine_osd_set_palette? + </para> + <para> + A: xine_osd_set_palette will set the entire 256 color palette + to be used when we blend the osd image. + "text palette" is a sequence of 11 colors from palette to be + used to render text. that is, by calling osd_render_text() + with color_base=100 will render text using colors 100-110. + </para> + <para> + Q: Can I render text with colors in my own palette? + </para> + <para> + A: Sure. Just pass the color_base to osd_render_text() + </para> + <para> + Q: Has a text palette change effects on already drawed text? + </para> + <para> + A: osd_set_text_palette() will overwrite some colors on palette + with pre-defined ones. So yes, it will change the color + on already drawed text (if you do it before calling osd_show, + of course). + If you don't want to change the colors of drawed text just + use different color_base values. + </para> + <para> + Q: What about the shadows of osd-objects? Can I turn them off + or are they hardcoded? + </para> + <para> + A: osd objects have no shadows by itself, but fonts use 11 + colors to produce an anti-aliased effect. + if you set a "text palette" with entries 0-9 being transparent + and 10 being foreground you will get rid of any borders or + anti-aliasing. + </para> + </sect3> + </sect2> + </sect1> + + <sect1> + <title>MRLs</title> + <para> + This section defines a draft for a syntactic specification of MRLs as + used by xine-lib. The language of MRLs is designed to be a true subset + of the language of URIs as given in RFC2396. A type 2 grammar for the + language of MRLs is given in EBNF below. + </para> + <para> + Semantically, MRLs consist of two distinct parts that are evaluated by + different components of the xine architecture. The first part, + derivable from the symbol <input_source> in the given grammar, is + completely handed to the input plugins, with input plugins signaling + if they can handle the MRL. + </para> + <para> + The second part, derivable from <stream_setup> and delimited from the + first by a crosshatch ('#') contains parameters that modify the + initialization and playback behaviour of the stream to which the MRL + is passed. The possible parameters are mentioned in the manpage to + xine-ui. + </para> + <para> + The following definition should be regarded as a guideline only. + Of course any given input plugin only understands a subset of all + possible MRLs. On the other hand, invalid MRLs according to this + definition might be understood for convenience reasons. + Some user awareness is required at this point. + </para> + <para> + EBNF grammar for MRLs: + <programlisting> + <mrl> ::= <input_source>[#<stream_setup>] + <input_source> ::= (<absolute_mrl>|<relative_mrl>) + <absolute_mrl> ::= <input>:(<hierarch_part>|<opaque_part>) + <hierarch_part> ::= (<net_path>|<abs_path>)[?<query>] + <opaque_part> ::= (<unreserved>|<escaped>|;|?|:|@|&|=|+|$|,){<mrl_char>} + <relative_mrl> ::= (<abs_path>|<rel_path>) + <net_path> ::= //<authority>[<abs_path>] + <abs_path> ::= /<path_segments> + <rel_path> ::= <rel_segment>[<abs_path>] + <rel_segment> ::= <rel_char>{<rel_char>} + <rel_char> ::= (<unreserved>|<escaped>|;|@|&|=|+|$|,) + <input> ::= <alpha>{(<alpha>|<digit>|+|-|.)} + <authority> ::= (<server>|<reg_name>) + <server> ::= [[<userinfo>@]<host>[:<port>]] + <userinfo> ::= {(<unreserved>|<escaped>|;|:|&|=|+|$|,)} + <host> ::= (<hostname>|<ipv4_address>|<ipv6_reference>) + <hostname> ::= {<domainlabel>.}<toplabel>[.] + <domainlabel> ::= (<alphanum>|<alphanum>{(<alphanum>|-)}<alphanum>) + <toplabel> ::= (<alpha>|<alpha>{(<alphanum>|-)}<alphanum>) + <ipv4_address> ::= <digit>{<digit>}.<digit>{<digit>}.<digit>{<digit>}.<digit>{<digit>} + <port> ::= {<digit>} + <reg_name> ::= <reg_char>{<reg_char>} + <reg_char> ::= (<unreserved>|<escaped>|;|:|@|&|=|+|$|,) + <path_segments> ::= <segment>{/<segment>} + <segment> ::= {<path_char>}{;<param>} + <param> ::= {<path_char>} + <path_char> ::= (<unreserved>|<escaped>|:|@|&|=|+|$|,) + <query> ::= {<mrl_char>} + <stream_setup> ::= <stream_option>;{<stream_option>} + <stream_option> ::= (<configoption>|<engine_option>|novideo|noaudio|nospu) + <configoption> ::= <configentry>:<configvalue> + <configentry> ::= <unreserved>{<unreserved>} + <configvalue> ::= <stream_char>{<stream_char>} + <engine_option> ::= <unreserved>{<unreserved>}:<stream_char>{<stream_char>} + <stream_char> ::= (<unreserved>|<escaped>|:|@|&|=|+|$|,) + <mrl_char> ::= (<reserved>|<unreserved>|<escaped>) + <reserved> ::= (;|/|?|:|@|&|=|+|$|,|[|]) + <unreserved> ::= (<alphanum>|<mark>) + <mark> ::= (-|_|.|!|~|*|'|(|)) + <escaped> ::= %<hex><hex> + <hex> ::= (<digit>|A|B|C|D|E|F|a|b|c|d|e|f) + <alphanum> ::= (<alpha>|<digit>) + <alpha> ::= (<lowalpha>|<upalpha>) + <lowalpha> ::= (a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z) + <upalpha> ::= (A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z) + <digit> ::= (0|1|2|3|4|5|6|7|8|9)</programlisting> + With <ipv6_reference> being an IPv6 address enclosed in [ and ] as defined in RFC2732. + </para> + </sect1> + +</chapter> |