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author | Jamieson Christian | 2003-12-11 00:51:51 +0000 |
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committer | Jamieson Christian | 2003-12-11 00:51:51 +0000 |
commit | f82a23771c95a7e70b4bc85c48d515853e289516 (patch) | |
tree | f2d7bc53ed9aa6e8189f2bd932305dc38133857c /sound | |
parent | c95e9d12a2dab1e49eaf8febaf063a76c0fc1d64 (diff) | |
download | scummvm-rg350-f82a23771c95a7e70b4bc85c48d515853e289516.tar.gz scummvm-rg350-f82a23771c95a7e70b4bc85c48d515853e289516.tar.bz2 scummvm-rg350-f82a23771c95a7e70b4bc85c48d515853e289516.zip |
Expanded the Doxygen docs for the MidiParser class.
Painfully detailed in its description of how to
get a MidiParser object hooked up and running.
Hope this helps ya, Joost! ;)
svn-id: r11559
Diffstat (limited to 'sound')
-rw-r--r-- | sound/midiparser.h | 141 |
1 files changed, 127 insertions, 14 deletions
diff --git a/sound/midiparser.h b/sound/midiparser.h index 502fd9c14f..d6d729103d 100644 --- a/sound/midiparser.h +++ b/sound/midiparser.h @@ -131,21 +131,134 @@ struct NoteTimer { // ////////////////////////////////////////////////// -//! A framework and common functionality for parsing MIDI streams. -/*! The MidiParser provides a framework in which to load - * parse and traverse MIDI streams. Loading and parsing - * events for specific formats requires a class to be - * derived from MidiParser. +//! A framework and common functionality for parsing event-based music streams. +/*! The MidiParser provides a framework in which to load, + * parse and traverse event-based music data. Note the + * avoidance of the phrase "MIDI data." Despite its name, + * MidiParser derivatives can be used to manage a wide + * variety of event-based music formats. It is, however, + * based on the premise that the format in question can + * be played in the form of specification MIDI events. * - * The MidiParser must be provided with a MidiDriver interface, - * which it uses to transmit events. However, it does NOT - * automatically hook into the MidiDriver's timer callback - * or set up its timer rate from the MidiDriver. The client - * using the MidiParser must set the timer rate and provide - * a means of firing the MidiParser's onTimer() method at - * appropriate intervals. The onTimer() event may be called - * by the client or by manually hooking and unhooking the - * MidiParser to the MidiDriver's timer callback. + * In order to use MidiParser to parse your music format, + * follow these steps: + * + * <b>STEP 1: Write a MidiParser derivative.</b> + * The MidiParser base class provides functionality + * considered common to the task of parsing event-based + * music. In order to parse a particular format, create + * a derived class that implements, at minimum, the + * following format-specific methods: + * - loadMusic + * - parseNextEvent + * + * In addition to the above functions, the derived class + * may also override the default MidiParser behavior for + * the following methods: + * - resetTracking + * - allNotesOff + * - unloadMusic + * - property + * - getTick + * + * Please see the documentation for these individual + * functions for more information on their use. + * + * The naming convention for classes derived from + * MidiParser is MidiParser_XXX, where "XXX" is some + * short designator for the format the class will + * support. For instance, the MidiParser derivative + * for parsing the Standard MIDI File format is + * MidiParser_SMF. + * + * <b>STEP 2: Create an object of your derived class.</b> + * Each MidiParser object can parse at most one (1) song + * at a time. However, a MidiParser object can be reused + * to play another song once it is no longer needed to + * play whatever it was playing. In other words, MidiParser + * objects do not have to be destroyed and recreated from + * one song to the next. + * + * <b>STEP 3: Specify a MidiDriver to send events to.</b> + * MidiParser works by sending MIDI and meta events to a + * MidiDriver. In the simplest configuration, you can plug + * a single MidiParser directly into the output MidiDriver + * being used. However, you can only plug in one at a time; + * otherwise channel conflicts will occur. Furthermore, + * meta events that may be needed to interactively control + * music flow cannot be handled because they are being + * sent directly to the output device. + * + * If you need more control over the MidiParser while it's + * playing, you can create your own "pseudo-MidiDriver" and + * place it in between your MidiParser and the output + * MidiDriver. The MidiParser will send events to your + * pseudo-MidiDriver, which in turn must send them to the + * output MidiDriver (or do whatever special handling is + * required). + * + * To specify the MidiDriver to send music output to, + * use the MidiParser::setMidiDriver method. + * + * <b>STEP 4: Specify the onTimer call rate.</b> + * MidiParser bases the timing of its parsing on an external + * clock. Every time MidiParser::onTimer is called, a bit + * more music is parsed. You must specify how many + * microseconds will occur between each call to onTimer, + * in order to ensure an accurate music tempo. + * + * To set the onTimer call rate, in microseconds, + * use the MidiParser::setTimerRate method. The onTimer + * call rate will typically match the timer rate for + * the output MidiDriver used. This rate can be obtained + * by calling MidiDriver::getBaseTempo. + * + * <b>STEP 5: Load the music.</b> + * MidiParser requires that the music data already be loaded + * into memory. The client code is responsible for memory + * management on this block of memory. That means that the + * client code must ensure that the data remain in memory + * while the MidiParser is using it, and properly freed + * after it is no longer needed. Some MidiParser variants may + * require internal buffers as well; memory management for those + * buffers is the responsibility of the MidiParser object. + * + * To load the music into the MidiParser, use the + * MidiParser::loadMusic method, specifying a memory pointer + * to the music data and the size of the data. (NOTE: Some + * MidiParser variants don't require a size, and 0 is fine. + * However, when writing client code to use MidiParser, it is + * best to assume that a valid size will be required. + * + * Convention requires that each implementation of + * MidiParser::loadMusic automatically set up default tempo + * and current track. This effectively means that the + * MidiParser will start playing as soon as timer events + * start coming in. + * + * <b>STEP 6: Activate a timer source for the MidiParser.</b> + * The easiest timer source to use is the timer of the + * output MidiDriver. You can attach the MidiDriver's + * timer output directly to a MidiParser by calling + * MidiDriver::setTimerCallback. In this case, the timer_proc + * will be the static method MidiParser::timerCallback, + * and timer_param will be a pointer to your MidiParser object. + * + * This configuration only allows one MidiParser to be driven + * by the MidiDriver at a time. To drive more MidiDrivers, you + * will need to create a "pseudo-MidiDriver" as described earlier, + * In such a configuration, the pseudo-MidiDriver should be set + * as the timer recipient in MidiDriver::setTimerCallback, and + * could then call MidiParser::onTimer for each MidiParser object. + * + * <b>STEP 7: Music shall begin to play!</b> + * Congratulations! At this point everything should be hooked up + * and the MidiParser should generate music. Note that there is + * no way to "stop" the MidiParser. You can "pause" the MidiParser + * simply by not sending timer events to it, or you can call + * MidiParser::unloadMusic to permanently stop the music. (This + * method resets everything and detaches the MidiParser from the + * memory block containing the music data.) */ class MidiParser { |