Goffredo Haus, editor
Fall 1995
© IEEE Computer Society Press.

3.5. Program Fragments and Example MIDI Files

Here are some of the routines to read and write variable-length numbers in MIDI Files. These routines are in C, and use getc and putc, which read and write single 8-bit characters from/to the files infile and outfile.

WriteVarLen (value)
register long value;

{

register long buffer;
buffer = value & 0x7f;
while ((value >>= 7) > 0)
{
buffer <<= 8;
buffer |= 0x80;
buffer += (value & 0x7f);
}
while (TRUE)
{
putc(buffer,outfile);
if (buffer & 0x80)
buffer >>= 8
else
break;
}
}

doubleword ReadVarLen () {

register doubleword value;
register byte c;
if ((value = getc(infile)) & 0x80)
{
value &= 0x7f;
do
{
value = (value << 7) + ((c = getc(infile)) & 0x7f);
} while (c & 0x80);
}
return (value);
}
As an example, MIDI Files for the following excerpt are shown below. First, a format 0 file is shown, with all inforrnation intermingled; then, a format 1 file is shown with all data separated into four tracks: one for tempo and time signature, and three for the notes. A resolution of 96 "ticks" per quarter note is used. A time signature of 4/4 and a tempo of 120, though implied, are explicitly stated.

Figure 10 - Example of 3 parts excerpt.

The contents of the MIDI stream represented by this example are broken down here:

Table XXVIII

The entire formats 0 and 1 MIDI file contents in hex follow. First, the header chunk, then, the track chunk.

Table XXIX

Table XXX

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