MIDICraft's MIDINET CD-ROM/MIDICraft's MIDINET CD-ROM.iso/DOSUTILS/MIDIIO.DOC

Text File | 1997-03-05 | 17KB | 467 lines

        ******************************
            MIDIIO v1.7

           standard midi input and output for C++
              by Guenter Nagler
                1995
          ([e-mail])
        ******************************

[0] FEATURES
    + parses binary midi files
    + writes binary midi files
    + copies binary midi files
    + sorts midi events by time
    + maps channels of binary midi files
    + checks validity of binary midi files

[1] BACKGROUND
My first midi parser was written in programming language "C".
It was impossible to reuse the C code in other programs in slightly
modified ways without duplicating the code.

In combination with the class facilities of "C++" (invented 1983 by
B. Stroustrup) it is very simple to reuse source code.

For my midi purpose I only needed to pack the knowhow of midi file format
parsing into a virtual base class. This class reads the midi file and
validates it. For all information in the midi song the parser calls a
function that usually does nothing in the base class but can be overwritten
in derived classes so that the owner of the derived class can act on midi
events like in event oriented programming method.

I used the midiio classes in various utilities:

+ The program midi2txt shows how the midi events are fired by the midi parser.
+ The program midifmt shows how to get the header information of a midi file
  using the midi parser.
+ The program midi2gm shows how midi files can be copied with
  modifications.

My wish to port the module and other utilities to Macintosh environment
failed because some Macintosh users told me that file handling is very
different to other machines.

[2] FILES DESCRIPTION

MIDIIO.CPP..........C++ implementation of midi parser and midi writer
MIDIIO.HPP..........C++ class definitions of midi parser and midi writer
MIDIIO.DOC..........some help to the C++ classes

[3] COPYRIGHT

MIDIIO (c) 1995 was created by Guenter Nagler.

MIDIIO is free and may be used as you wish with this one exception:

    You may NOT charge any fee or derive any profit for distribution
    of MIDIIO.  Thus, you may NOT sell or bundle MIDIIO with any
    product in a retail environment (shareware disk distribution, CD-ROM,
    etc.) without permission of the author.

You may give MIDIIO to your friends, upload it to a BBS, or ftp it to
another internet site, as long as you don't charge anything for it.

[4] DISCLAIMER

MIDIIO was designed to handle 100% compatible midi files.
It was tested with 600 different midi files but I can not say if
each 100% midi compatible midi file can be correctly converted.
So I give no guarantees of the results, especially with non 100%
compatible midi files.
If you find a midi file that you think to be 100% compatible midi
that is not correctly parsed or copied, please send a sample file to
[e-mail] .

Use MIDIIO at your own risk.  Anything you do with MIDIIO is your
responsibility, and not the author's.  Any damage caused to any person,
computer, software, hardware, company, or business by running MIDIIO
is your responsibility, and the author will not be liable.

If you don't understand these terms, or are not sure of something, or
are afraid something bad might come of using MIDIIO, don't  use  it!
You are here forewarned.

[5] Compile

Use a C++ compiler to compile and link

e.g.

   g++ -o program program.cpp midiio.cpp otherfiles.cpp

Force the compiler to compile C++ code!
Some compilers use the file extension to decide compile mode.
If you compiler compiles only .C files then rename the file extension.


[6] USAGE
midiio.hpp defines following classes:

class MidiRead;
class MidiWrite;
class MidiCopy;
class MidiSerial;

Include the header file into your source:
#include "midiio.hpp"

CONSTRUCTION

All of theses need a filename to construct an instance of this class.
The class opens or creats a file with that filename.
MidiRead and MidiCopy allow to use an already opened file handle, so that
the filename is only stored but not used by the base classes.
The constructors do not write or read data.

Dynamic construction of a parser class:

    MidiRead *read = new MidiRead(input_filename);

Automatic construction of a writer class:

    MidiWrite midiwrite(output_filename);

Construction of a class using an open file:

    FILE* inputf = fopen(input_filename, READ_BINARY);
    if (!inputf)
      error...
    MidiCopy midicopy(input_filename, inputf);

Construction of a serial midi reader:
        MidiSerial* serial = new MidiSerial(input_filename);

TEST IF CONSTRUCTION WAS SUCCESSFUL

    MidiRead* midiread = new MidiRead(filename);
    if (!midiread)
      not enough memory
    else if (midiread->getf())
      file filename not found
    else
      use midiread as parser

DESTRUCTION

If automatic construction was used then destructor is called automatically.
if dynamic construction was used (new ...) then you must call delete operator

  MidiRead* midiread = new MidiRead(filename);
  ...
  delete midiread;

The destructor frees memory allocated by the class and finishs writing of
midi files and closes the file if it was opened by the class constructor.


PARSING MIDI FILES

Following functions parse midi files or parts of midi files:
  int run();         // parses full midi file
  int runhead();     // parses only header of midi file
  int runtrack(int trackno);   // parses a single track
  int runevent(long trackend);    // parses a single midi event

run() and runhead() automatically parse from the beginning of the file.
run() automatically calls the other functions for parsing special parts
of the file. In MidiRead and MidiCopy run() delivers events tracks by tracks.
In MidiSerial it delivers events sorted by time.

For direct use of runtrack() and runevent() the file must be positioned
to a valid file position (use MidiRead::seek) that it will work properly.
(E.g. you get the file positions by running in different passes, first
  call run() and collect positions when reaching the position of track
  or certain event, and call runtrack() or runevent() when run()  is ready,
  see mididrum.cpp for use of these special parsing technic).

Following functions are called by the parser while working or
when errors are found:

virtual void error(const char* msg); // found midi file format error, you should abort the procedure
virtual void warning(const char* msg); // found harmless error or incompatibility
virtual void percent(int perc);     // percentage 0..100 of parsed midi file, could be confusing if not
                // sequentially parsing like run() does

run() and runhead() call the function head() with header information:
    virtual void head(unsigned version, unsigned tracks, unsigned unitperbeat);

run() calls the function end() at end of midi file parsing

run() runtrack() call the functions

virtual void track(int trackno, long length, int channel); // at beginning of a track
virtual void endtrack(int trackno); // at end of a track

A track is a part of a song played by a certain group of instruments.
All tracks are playing together at same time.

run() and runtrack() call the time() function between all midi events
that delivers the pause between two midi events of this track.
run() and runtrack() call runevent() to parse single events.

runtrack() can be aborted by setting member variable skiptrack_ to 1.

runevent() calls a function for each different midi event type.
Some event types belong to a group and an option flag controls if
the group function or the specialized functions are called.

The option OPTION_NOCONTROLS controls if the function control() is called
rather than one of the functions:
    highbank(), wheel(), breath(), foot(), portamentotime(), data(),
    volume(), balance(), expression(), lowbank(), hold(), reverb(),
    chorus(), datainc(), datadec()

The option OPTION_NOEVENTS controls if the function rather calls only track() and endtrack()
or the time() and all the midi event functions functions too.

The option OPTION_NOMETAEVENTS controls if the function meta() is called
rather than one of the functions
    seqnumber(), smpteofs(), key(),    prefixchannel(), prefixport(),
    text(),    end(), tact(), tempo()

The option OPTION_NOSYSEVENTS  controls if the function sysex() is called
rather than one of the functions
    gmreset(), gsreset(), gsexit()

In case that the special coding is not known as standard event the
group function is called.

The parser options can be assigned to the public member variable
MidiRead::options_ . If more than one options are set then use the | operator
to combine them (e.g. midiread->options_ = OPTION_NOSYSEVENTS | OPTION_METAEVENTS; ). By default all special functions are called rather than their
group function.

Group functions help to treat events of same type common, if it is not
not necessary to distinguish them.

See midi2txt implementation as a good example for the midi parser.

See midifade implementation as example for calculating midi time to
real time.

See mididmp implementation as example for sorting midi events by real time.

WRITING MIDI FILES

1. construct an instance of a midi writer
    MidiWrite *midiwrite = new  MidiWrite(output_filename);
    if (!midiwrite)
      error out of memory
    if (!midiwrite.getf())
      error cannot create file

2. generate the midi header
    midiwrite->head(VERSION_SINGLECHANNEL, 0, resolution);

   You need to know with format you want to write:
   VERSION_SINGLECHANNEL:  only one track that contains whole song (preferred format)
   VERSION_MULTICHANNEL:   a tempo track and one or more tracks that
               contain only events of certain midi channel
               (different tracks could use same channel)
   VERSION_MULTISONG:       each track contains a whole song (rarely used)

   You need to know which note resolution (= units per quarternote) you use:
   Usually values 96, 120, 384 are used.
   The value should be computable by:    resolution = 3 * 2 * 2 * 2 * ... * 2

   The number of tracks will be updated automatically, when the destructor of the
   class is called.

3. generate track
   midiwrite->track();

   it depends on the chosen format (version) which events you should
   generate in this track:

   VERSION_SINGLECHANNEL:
      first track (tempo track) should contain only events that have no
      channel parameter,
      for each other track you should select one channel (0-15) and use
      events that have no channel parameter or events generated with this
      channel number. Only the first track should contain tempo or tact
      events.

   VERSION_MULTICHANNEL:
      Only one track is to generate and contains any events.

   VERSION_MULTISONG:
      Each track is a song (as in VERSION_MULTICHANNEL) and contains
      any events.

4. generate pause to start of next event
   midiwrite->time( pause_units );

   A quarternote has  midiwrite->unitsperquarter()  midi units.

   The time will be written to the file when you generate an event or
   close the track.
   You can call it several and the function will add it to the current pause.

   The function getcurtime() delivers the total midi time units since start
   of the track inclusive already chosen pause to the following event.

   You can reset current pause to 0 with call of function cleardelta().

   You can set current pause to a certain value by following sequence:
    midiwrite->cleardelta();
    midiwrite->time(newpause);

5. generate event
   use one of many event functions:

   Some functions are usable for a whole group of events:

void event(int what, int len, unsigned char* data); // write any event
void meta(int what, int len, unsigned char* data); // write meta events
void sysex(int syslen, unsigned char* sysdata); // write sysex events
void text(int what, int len, unsigned char* txt); // write text meta events
     // use defines meta_ in header for what parameter
void control(int channel, int what, int val);   // write control event

The special events are similiar to the events in the midi parser.

6. closing the track
  You can enter pauses and events as many as you want into a track.
  When you are ready you should close the track:

  midiwrite->endtrack();

  This will call MidiWrite::end() automatically to append an end of track
  event to the track once and updates the length of the track.

7. closing the midi file
  Repeat writing tracks until enough tracks are written.
  The midifile is finished when the destructor of the class is called.

  Therefor you use
      delete midiwrite
  or wait until the program leaves the block { ... } wherein the
  instance was automatically constructed.

  The destructor updates the length of the file, updates the number of
  tracks and flushes cached data to the file.

  if  the file was opened by the class itself the file handle is
  closed automatically, otherwise you need to close it after the
  class was destructed.

  Now the midi file is ready.
  Use midi2txt to test if the resulting file is valid and contains
  the correct information.

  See midi0to1 and midi1to0 how midi files are read and stored in an other format.

MODIFIYING MIDI FILES
  The class MidiCopy reads a midifile and writes it in same format
  to another file. While copying the channels can be mapped.

  By derivation of class MidiCopy minor changes to the
  file are possible.

1. derivation of class MidiCopy

class MidiChange : public MidiCopy
{
public:
  MidiChange(char* name);

  virtual void track(int trackno, long length, int channel);
  // specify all virtual functions that change
};

void MidiChange::track(int trackno, long length, int channel)
{
    MidiChange::track();

    // e.g. add some events at beginning of track
    char* copyright = "(c) G. Nagler";
    MidiChange::text(meta_copyright, strlen(copyright), "copyright", copyright);
}

2. construct a parser object from own type

  MidiChange midi(input_filename);
  if (!midi.getf())
    error cannot open ...

3. construct a midi writer object
  MidiWrite* write = new MidiWrite(output_filename);
  if (!write)
    error not enough memory
  if (!write->getf())
    error cannot create midi file

4. connect midi parser and midi writer
  midi.setoutput(write);

5. set channel mapping option if wanted
  for (int c = 0; c < 16; c++)
    midi.mapchannel(c, map[c]);
6. set channel ignore option if wanted
  midi.ignorechannel(9);

7. set parser options if wanted
  midi.options_ = OPTION_NOEVENTS;

8. start midi parser
  if (!midi.run())
    fprintf(stderr, "%s: midi read error at %04lX\n", input_filename, midi.getpos());

9. close output midi file by destructing object
  delete write;

You can add events, ignore events, replace events using this technic:
e.g. change volume, change speed, change programs, transpose notes, ...

See midi2gm example that adds and ignores events to make midi files more
general midi compatible.

Use getcurunit() to ask current in midi units.
Use getcurmillisec() to ask current time since start of track.
Hints:
  Use this time information only in first track and
  do not specify option OPTION_NOREALTIMEEVENTS or OPTION_NOMETAEVENTS
  because these options ignore tempo changes and tempo changes are
  only available in first track.

[7] SUGGESTIONS / COMMENTS / BUG REPORTS / QUESTIONS

         WWW:    http://hgiicm.tu-graz.ac.at/Cpub
          contains all my dos/unix midi programs
         EMAIL:  [e-mail]

[8] CHANGES
v1.0 to v1.1:
  * some portability changes for UNIX compatibility

v1.1 to v1.2
  * midiio engine writes less compressed but safer files (more compatibility
    to weak midi readers)

v1.2 to v1.3
  * added option -version
  * added class MidiCopy for modifying midi files

v1.3 to v1.4
  * better sysex support (unusual and elder variants)
  * all functions are of MidiRead are now public, that reading midi files
    can be done without functions runhead() runevent(), runtrack(), run()

v1.4 to v1.5
  * File I/O in separate base class MidiBuffer
  * MidiBuffer allows preloading loading of file into memory
  * MidiBuffer allows work on memory midi data (in DOS realtime mode
    limited to 32 KB!, in protected mode or 32bit environments not limited)
  * MidiRead: current time position available by function getcurmillisec()
  * MidiRead: current beat number available by function getcurbeat()

v1.5 to v1.6:
  * added class MidiSerial that reads a midi file and delivers events
    sorted by time (also see sample program midinote.zip)

v1.6 to v1.7:
  * added skiptrack_ member to abort function runtrack if wanted
  * removed exit(1) if track is incomplete, trying to skip the track with
    skiptrack_