AWCMF - Creative Music File format player

Introduction

xcmf is a graphical interface to play CMF music files. CMF stands for Creative Music Format. CMF is very similar to MIDI format, the difference being, that in CMF music files, the instrument patches are stored inside the file and the intrument patches are designed for the FM synthesizer only. xcmf provides a tape-player like interface with buttons for play, fastforward, rewind, and stop. There are controls for changing playback speed and volume.

Control Buttons

• Tempo - This slider increases or decreases the tempo of the song during playback.
• Volume - This slider increases or decreases the volume of the song during playback. ·
• Rewind - This button rewinds the CMF file. During rewinding, notes are play in reverse order.
• Play - This button plays the CFM music file on the FM synthesizer
• Forward - This button is used to fast-forward the song.
• Stop - This button stops playing, fast-forwarding or rewinding the CMF file.

Playing a CMF file

In order to play a CMF music file, you must first select a CMF file from the file menu. A selection box pops up and displays the list of CMF files. Select a file and then press the OK button. Finally, press the Play button. You may change the speed or the volume at any time. You may also press the Rewind or the Fast-forward buttons at any time to seek to a position in the CMF file. While seeking backwards or forwards, you may press the Stop button or the Play button to continue playing the file. In order to play a new song, the xcmf must be in a “stopped” state.

CMF File Format

CMF files are organized in three separate blocks, namely, the

• Header block which contains the timing values and offsets of other blocks
• Instrument block which contains the definitions of the FM synthesizer instruments. Instruments are stored in SBI format which is a 16 byte record. The number of records depends on the number of instruments stored in the CMF header (see below).
• Music block which contains the notes in Standard MIDI format (SMF). It is single-track multi-channel and polyphonic. The maximum number of channels is 16. MIDI Control Events in CMF files are described as follows:

Control Number	Control Data	Description
0x66		1 - 127		Music markers

0x67		0 or 1		If 0, then all the channels are 
				designated as melody channels. 
				If 1, then channels 12 - 16 are 
				designated as rhythm channels and
				channels 1 - 11 are melody.
				12 - Bass drum, 13 - Snare, 
				14 - Tomtom, 15 - Cymbal, 16 Hihat

0x68		0 - 127		Pitch Bend Up by 1/128th of a semitone. 
				A value of 64 implies that the pitch is
				changed only by 1/2 a semitone.
				
0x69		0 - 127		Pitch Bend down by 1/128 of a semitone.
				A value of 64 changes the pitch by 1/2 a
				semitone.

OFFSET (Bytes)	DESCRIPTION
00 - 03	        File ID - “CTMF”

04 - 05	        File format version - byte 04 = MSB, byte 05 = LSB. 
                Current version 1.1

06 - 07	        Offset of the instrument block

08 - 09	        Offset of the music block

0A - 0B	        Ticks per quarter note (one beat) 
                Number of timer ticks equivalent to a quarter note. 
                If the timer is set to 96Hz and the tempo is 120, 
                this value is 48.

0C - 0D	        Clock ticks per second - default is 96

0E - 0F         Offset of the music title.	
                The title must be a null-terminated ASCII string. 
                If this offset is 0 it means there is no music title in the CMF file.

10 - 11	        Offset of the composer’s name. 
                The name must be a null-terninated ASCII strings. 
                If this offset is 0 then there is no name in the CMF file.

12 - 13	        Offset of Remarks. 
                The remarks must be a null-terminated ASCII string. 
                If this offset is 0 it means there is no remarks title in the CMF file. 
                The remarks string must be at most 32 characters including the null char.

14 - 23	        Channel in use table 
                This 16 byte table indicates which of the 16 FM channels 
                are being used by the CMF file. 
                If a channel is in use then the corresponding byte is set to 1

24 - 25	        Number of instruments Used. 

26 - 27	        Basic tempo - the  tempo used in the CMF file

28              Title, remarks begin here.