While developing the games Sqrxz and Solid Gold I needed a Protracker
player which can insert sound effects from the game into the current song.
I ended up in writing a completely new player based on the original
replayer source which came with ProTracker 2.3.
This player is quite optimized and has some useful features for game
developers:
- Insert external sound effects into the replayed module.
- Can also play sound effects while music is stopped or not even initialized.
- A fast master volume for the replayed music.
- No busy waiting. DMA and repeat pointers are set with timer interrupts.
- Optionally works without timer interrupts at all.
- E8 command can be used as a trigger for your main program.
- Lots of tables for best performance. No multiplications or divisions.
The sound fx system gives you the possibility to play samples on a channel
of your choice or on the channel which the player thinks is the best one.
It may be a channel which is currently not replaying music and/or has
the longest period of inactivity ahead. This has the effect that the
replayed song is often not disturbed at all.
Up to four sound effects can be played at the same time and any of them
has its own priority, which is especially useful when trying to play
several sounds on the same channel. You may for example define that a
shooting-sound has a higher priority than a jumping-sound.
For automatic channel selection you can additionally reserve specific
channels for music only, or define the maximum number of channels which
may be used for sound effects at once.
The master volume is always applied to the music, but does never affect
external sound effects.
NOTE: When playing external sound effects, always make sure the first
word is cleared! It is used for idling when the effect stopped. This
is the same technique as used by the music samples in Amiga trackers.
(Alternatively, refer to the NULL_IS_CLEARED option.)
How to use:
1. Selecting the data model
ptplayer.asm can be configured to support two data models:
a) By default ptplayer.asm assembles into a single code section. The
player routines set up a local base register to access data.
This requires a working RS directive, which is provided by many
assemblers, like e.g. vasm, PhxAss, Devpac, Basm, AsmOne, SNMA.
b) By defining the SDATA symbol, ptplayer.asm assembles into a code
section and a small-data section (called __MERGED). All player
routines expect that the base register A4 is set up with the
small-data base pointer (provided by the linker through _LinkerDB).
It uses the NEAR directive, which might work with vasm and PhxAss only.
2. Selecting optional features
By default ptplayer builds the CIA-B timer version, for games/demos which
take over the hardware, with all features included:
MINIMAL=0, ENABLE_SAWRECT=1, NULL_IS_CLEARED=0, NO_TIMERS=0,
VBLANK_MUSIC=0 and OSCOMPAT=0.
a) By defining the symbol MINIMAL=1 (defaults to 0) you get just a
standard Protracker player, without the ability to insert external
sound effects or to control the master or sample volumes.
This approximately halves the code size.
b) By defining the symbol ENABLE_SAWRECT=0 (defaults to 1) you may
disable sawtooth and rectangle vibratos/tremolos. When disabled,
they are replaced by sine-waves. These wave forms are extremely
rare and disabling them saves another 2K for the tables.
c) By defining the symbol NULL_IS_CLEARED=1 (defaults to 0) you indicate
that the memory locations $0 and $1 in your system are zero, so they
will be used for idle-looping of audio channels. Might be useful when
dynamically loading new samples.
d) Setting NO_TIMERS=1 disables the use of both CIA-B timers completely,
which means that the player doesn't depend on level-6 EXTER interrupts
anymore. NO_TIMERS=1 automatically includes VBLANK_MUSIC=1 (see below).
With NO_TIMERS set, your main program has to call all music subroutines
itself. The typical procedure in a VERTB-based main loop would be:
1. call _mt_music
2. wait at least 550 ticks, then call _mt_dmaon
3. wait at least 550 ticks again, then call _mt_setrep
The last two steps could for example be done by Copper interrupts.
CAUTION: You should know what you do, if you use this mode! It is up
to you to take care that calling a ptplayer function is not interrupted
by another ptplayer function.
e) Define VBLANK_MUSIC=1 (defaults to 0) if you don't want ptplayer
to set up a CIA-B Timer-A interrupt for music replay, which means
you cannot set the tempo with the F-command anymore (only the speed)
and you have to call _mt_music yourself out of your own VBlank
interrupt handler. Also sound effects will no longer work, when no
music is playing.
NOTE: CIA-B Timer-B is still used for enabling Audio DMA and setting
the loop pointers (unless you define NO_TIMERS=1). So it doesn't free
the Level-6 interrupt vector. This is just an option if you must
synchronize your music with your game or demo running in VBlank interrupts.
f) Define OSCOMPAT=1 (defaults to 0) to build a ptplayer-version which
uses AmigaOS to register CIA interrupts and allocates all audio channels
via audio.device. The default version is a little bit faster and
smaller, but may NOT work correctly with AmigaOS alive!
Note, that _mt_install and _mt_remove take different arguments, when
OSCOMPAT is set.
You may change these symbols either directly in the source or override
them via the assembler's command line.
3. Common usage (standard version with CIA-B timer interrupts)
a) Install a Level-6 interrupt handler for CIA-B timer interrupts by
calling _mt_install. Do this once, during program init.
b) For every new MOD file to play initialize it with _mt_init.
Most common case is to pass a pointer to the MOD in A0 and set A1
and D0 to zero, which will play the song from the beginning.
Everything is initialized for replay now, but nothing is played.
c) Set the byte-variable _mt_Enable to non-zero to start the replay.
Clearing that variable again pauses the song.
VBLANK_MUSIC=1: You have to call _mt_music yourself out of a 50Hz
interrupt. _mt_Enable is ignored in this case.
d) Stop playing and set all volumes to zero by calling _mt_end.
e) Finally, in the cleanup routine of your program, remove the Level-6
interrupt handler again and reset all CIA registers by calling
_mt_remove.
4. Common usage (NO_TIMERS=1)
a) For every new MOD file to play initialize it with _mt_init.
Most common case is to pass a pointer to the MOD in A0 and set A1
and D0 to zero, which will play the song from the beginning.
Everything is initialized for replay now, but nothing is played.
b) As with VBLANK_MUSIC=1, you have to call _mt_music 50 times per
second to play the MOD. For example out of a VERTB interrupt.
Then wait for at least 550 ticks (12 raster lines) and call _mt_dmaon.
Thereafter wait for at least another 550 ticks and call _mt_setrep.
c) Stop playing and set all volumes to zero by calling _mt_end. Also
make sure that you don't call _mt_music, _mt_dmaon or _mt_setrep
anymore.
Exported functions:
Note, that the leading underscore disappears when a symbol is referenced
from C (you can use ptplayer.h to include all prototypes).
CUSTOM is the Amiga custom-chip base address $dff000.
Also note that the arguments for _mt_install and _mt_remove differ,
depending on whether you have built ptplayer with OS-compatibility
enabled (define OSCOMPAT) or not. When calling the OS-compatible
ptplayer routines from C, define __OSCOMPAT before including ptplayer.h.
[OSCOMPAT=0] _mt_install(a6=CUSTOM, a0=VectorBase, d0=PALflag.b)
Install a CIA-B interrupt for calling _mt_music or mt_sfxonly
automatically. The music module is replayed via _mt_music when _mt_Enable
is non-zero. Otherwise the interrupt handler calls mt_sfxonly to play
sound effects only.
VectorBase is 0 for 68000, otherwise set it to the CPU's VBR register.
A non-zero PALflag selects PAL-clock for the CIA timers (NTSC otherwise).
[OSCOMPAT=1] ok = _mt_install()
Register CIA-B interrupts with AmigaOS for calling mt_music or
mt_sfxonly. Allocate all Paula audio channels via audio.device.
The music module is replayed via _mt_music when _mt_Enable is non-zero.
Otherwise the interrupt handler calls mt_sfxonly to play sound
effects only.
Returns true (1) on success, false (0) otherwise.
You must not call _mt_remove(), when _mt_install() failed!
[OSCOMPAT=0] _mt_remove(a6=CUSTOM)
Remove the CIA-B music interrupt, restore the previous handler and
reset the CIA timer registers to their original values.
[OSCOMPAT=1] _mt_remove()
Unregister the CIA-B interrupts handlers and deallocate all
audio channels.
_mt_init(a6=CUSTOM, a0=TrackerModule, a1=Samples|NULL, d0=InitialSongPos.b)
Initialize a new module.
Reset speed to 6, tempo to 125 and start at the given song position.
Master volume is at 64 (maximum).
When a1 is NULL the samples are assumed to be stored after the patterns,
which is the usual case.
_mt_end(a6=CUSTOM)
Stop playing the current module and sound effects.
_mt_soundfx(a6=CUSTOM, a0=SamplePointer,
d0=SampleLength.w, d1=SamplePeriod.w, d2=SampleVolume.w)
Request playing of an external sound effect on the most unused channel.
This function is for compatibility with the old API only.
You should call _mt_playfx instead. MINIMAL=0 only.
channelStatus = _mt_playfx(a6=CUSTOM, a0=SfxStructurePointer)
Request playing of a prioritized external sound effect, either on a
fixed channel or on the most unused one.
Structure layout of SfxStructure:
void *sfx_ptr (pointer to raw sample start in Chip RAM, even address)
WORD sfx_len (sample length in words)
WORD sfx_per (hardware replay period for sample)
WORD sfx_vol (volume 0..64, is unaffected by the song's master volume)
BYTE sfx_cha (0..3 selected replay channel, -1 selects best channel)
BYTE sfx_pri (priority, must be in the range 1..127)
When multiple samples are assigned to the same channel the lower
priority sample will be replaced. When priorities are the same, then
the older sample is replaced.
The chosen channel is blocked for music until the effect has
completely been replayed.
RETURN VALUES: A pointer to a channel-status structure (see ptplayer.h)
when the sample is scheduled for playing, or NULL when the request was
ignored.
NOTE: Remember that sfx_ptr points to raw sample data (no IFF header
or similar). And always make sure the first two bytes of your sound
effect sample are zero! Alternatively, refer to NULL_IS_CLEARED.
MINIMAL=0 only.
_mt_loopfx(a6=CUSTOM, a0=SfxStructurePointer)
Request playing of a looped sound effect on a fixed channel, which
will be blocked for music until the effect is stopped (_mt_stopfx).
It uses the same SfxStructure as _mt_playfx, but the priority is
ignored. A looped sound effect has always highest priority and will
replace a previous effect on the same channel. No automatic channel
selection is possible!
Also make sure the sample starts with a zero-word, which is used
for idling when the effect is stopped by _mt_stopfx. This word is
included in the total length calculation, but excluded when actually
playing the loop. MINIMAL=0 only.
_mt_stopfx(a6=CUSTOM, d0=Channel.b)
Immediately stop a currently playing sound effect on a channel (0..3)
and make it available for music, or other effects, again. This is the
only way to stop a looped sound effect (_mt_loopfx), besides stopping
replay completely (_mt_end). MINIMAL=0 only.
_mt_musicmask(a6=CUSTOM, d0=ChannelMask.b)
Bits set in the mask define which specific channels are reserved
for music only. Set bit 0 for channel 0, ..., bit 3 for channel 3.
Additionally a cleared bit prevents any access to the sample pointers
of this channel.
When calling _mt_soundfx or _mt_playfx with automatic channel selection
(sfx_cha=-1) then these masked channels will never be picked.
The mask defaults to 0. MINIMAL=0 only
_mt_mastervol(a6=CUSTOM, d0=MasterVolume.w)
Set a master volume from 0 to 64 for all music channels.
Note that the master volume does not affect the volume of external
sound effects (which is desired). MINIMAL=0 only.
_mt_samplevol(d0=SampleNumber.w, d1=Volume.b)
Redefine a sample's volume. May also be done while the song is playing.
Warning: Does not check arguments for valid range! You must have done
_mt_init before calling this function!
The new volume is persistent. Even when the song is restarted.
MINIMAL=0 only.
_mt_channelmask(a6=CUSTOM, d0=ChannelMask.b)
Bits cleared in the mask define which specific channels are muted
for music replay. Clear bit 0 for channel 0, ..., bit 3 for channel 3.
The mask defaults to all channels unmuted (bits set) and is reset to
this state on _mt_init and _mt_end. MINIMAL=0 only.
_mt_music(a6=CUSTOM)
The replayer routine. Can be called from your own VERTB interrupt
handler when VBLANK_MUSIC or NO_TIMERS is set. Is otherwise called
automatically by Timer-A interrupts after _mt_install.
_mt_dmaon()
NO_TIMERS=1 only!
MUST be called ca. 550 ticks after calling _mt_music. Enables Audio
DMA to play a new note.
_mt_setrep()
NO_TIMERS=1 only!
MUST be called ca. 550 ticks after calling _mt_dmaon. Sets the
repetition pointers and lengths for looped samples.
Exported byte-sized variables:
_mt_Enable
Set this byte to non-zero to play music, zero to pause playing.
Note that you can still play sound effects, while music is stopped.
It is set to 0 by _mt_install. No effect, when VBLANK_MUSIC or
NO_TIMERS is set.
_mt_E8Trigger
This byte reflects the value of the last E8 command.
It is reset to 0 after _mt_init.
_mt_MusicChannels
This byte defines the number of channels which should be dedicated
for playing music. So sound effects will never use more
than 4 - _mt_MusicChannels channels at once. Defaults to 0.
MINIMAL=0 only.
There is also a header file for C compilers, called ptplayer.h.
It depends on the SDI_compiler.h header file, which implements
portable macros for defining compiler-specific register arguments.
Get it from Aminet: http://aminet.net/dev/c/SDI_headers.lha
License:
Written by Frank Wille in 2013, 2016 - 2024.
I, the copyright holder of this work, hereby release it into the public
domain. This applies worldwide.
If still in doubt, please read the included file "LICENSE".
FAQ:
- The player doesn't work. I'm hearing no music.
A: This can have multiple reasons. Most likely is that you didn't
call _mt_install at all or with a wrong Vector Base pointer (OSCOMPAT=0).
The Vector Base is 0 for 68000 systems. Otherwise you *must* read
it from the CPU's VBR register, which is only available in supervisor
mode. Also don't forget to set _mt_Enable to true to start playing.
The default version of ptplayer is intended for games/demos which take
over the hardware and disable the OS. Running with the OS alive may work,
as the OS doesn't use the CIA-B timers, but it is not recommended.
If you want the player to use and run under AmigaOS, define OSCOMPAT=1.
- I want to run the player in VERTB interrupt.
A: You have two options. Either define VBLANK_MUSIC=1 to free CIA-B
Timer-A and call the music replay routine _mt_music 50 times per
second yourself (Timer-B is still used for DMA enable and looped
samples), or define NO_TIMERS=1 to free all timers and don't use any
level 6 interrupts. In the last case you also have to call _mt_dmaon
and _mt_setrep after at least 550 ticks to make music replay work.
- I am hearing a high-pitched noise in my music.
A: Amiga players use the first two bytes of a sample for idle-looping.
Make sure they are zeroed.
Alternatively, assemble ptplayer with NULL_IS_CLEARED=1 and make sure
the bytes at $0 and $1 are zero.
- I am hearing a high-pitched noise when playing an empty sample.
My first initialized sample is looped or unused, so how can that be?
A: Check the first two bytes of your first initialized sample.
These bytes are used by ptplayer for all empty samples.
Alternatively, assemble ptplayer with NULL_IS_CLEARED=1 and make sure
the bytes at $0 and $1 are zero.
- I am hearing a high-pitched noise after playing a sound effect.
A: The same technique is used for playing sound effects as for
playing instrumental samples. The sound effect idles in the first
two bytes after being played. So make sure they are zero.
- But I don't want to clear the first two bytes in sound effects.
A: Then make sure that the bytes at address $0 and $1 are zero, and
assemble the player with NULL_IS_CLEARED=1.
- I am hearing some clicking noise at the beginning of a sound effect.
A: Make sure your sample pointer points to the raw sample data, and
not to any form of file header (e.g. IFF-8SVX, etc.). When loading
external sound effects you have to parse the file header yourself.
History:
3.0:
- Try not to break channels with sound effects, which are currently
playing a looped sample.
- Sound effects can also be started when the music is not playing
(_mt_Enable=0).
3.1:
- Do not trash d2/a2 in _mt_init.
- Unused samples with length 0 are played like a 1-word null-sample,
for compatibility with other players.
- Make sure all samples start with two zero-bytes.
4.0:
- For better maintenance there is only a single source text now. The
default is a PC-relative, single-section version, which uses a local
base register. Small data mode can be enabled by defining SDATA.
- _mt_install also initializes the channel structures, like _mt_init
does. So it should be possible to play sound effects without loading
a tracker module.
- New sound effects system, which truly supports playing multiple sound
effects per frame (e.g. stereo). It also supports priorities and
channel selection.
- New exported function _mt_playfx which passes a pointer to an sfx
structure, includes the new parameters like channel and priority.
The old API through _mt_soundfx is still supported and emulated by
_mt_playfx.
- New exported function _mt_musicmask defines which specific channels
are dedicated for music and won't be used for sound effects.
- New exported variable _mt_MusicChannels defines a limit for the
maximum number of channels to be used for sound effects in parallel.
5.0:
- Only few assemblers support the BASEREG directive, so I decided
to rework the code and make it more portable. This version is tested
with Devpac, vasm, PhxAss, Barfly-Asm, SNMA, AsmOne, AsmPro.
- All exported symbols (functions and variables) have got a leading
underscore now, to make them directly accessible to C programs.
So in assembler you have to call _mt_init now, while in C you can
call mt_init.
5.1:
- Included C header file, ptplayer.h, provided by BSzili.
- Fixed bug where other level 6 interrupts could trigger sample replay.
- Eliminated relocations in the fine-tune table, by replacing pointers
with word-offsets (asman).
- More optimizations in the Timer B interrupt handlers and made it
PC-relative (asman).
- Include a public domain license.
5.2:
- Make it work with broken mods, which have a sample repeat length of zero.
- Never break looped samples with sound effects, except we have looped
samples on all four channels at once!
- New variable _mt_SongEnd to automatically stop the song when having
played the last position. Don't use it! Doesn't work perfectly yet.
5.3:
- No longer clear the first word of each sample for idle looping.
Either we have a good Amiga tracker MOD with repeat-length one, which
already cleared that word, or we have a PC tracker MOD with a zero
repeat length. In the latter case the idle loop will now point to
address $0. Make sure that the word at this address is cleared!
- Treat samples with a length of one word the same as with zero length
as a workaround for broken PC trackers.
- Changed APTR to void* in the C headers, for better Kickstart 1.x
OS header file compatibility.
- Fixed detection of negative fine-tuning (broken due to optimizations
in V5.1).
6.0:
- _mt_musicmask works as documented now! Sound effects will never play
on the masked channels. Previously it was rather a hint not to use them.
- Fixed sign-bug in tremolo/vibrato command 7xx (Antiriad/EAB).
- New function _mt_samplevol may be used to redefine a sample's volume.
- _mt_playfx now returns a pointer to the selected channel status structure
when the sample was scheduled for playing and returns NULL when ignored.
- Wait 576 ticks for audio DMA instead of 496, which fixes issues with
low notes on a few A1200 configurations. (No, this doesn't harm the
player's performance, as it is a timer interrupt.)
- Defining the symbol MINIMAL lets you assemble a minimal version of
the player, without the ability to insert sound effects and without
master-volume or changing samples volumes.
- Improved interrupt handling, following a suggestion of Ross/EAB.
- Minor optimizations.
6.1:
- Fixed note delay command (EDx), which still played the previous note
in some situations (Antiriad/EAB).
- Fixed sample-offset command (9) with empty note-field (h0ffman/EAB).
- _mt_mastervol must change the volumes of all channels immediately
and shouldn't wait for the next sample being played (suggested by
h0ffman/EAB).
- Symbol ENABLE_SAWRECT may be used to disable sawtooth and rectangle
waveforms for vibrato and tremolo, which saves memory for their tables
(suggested by Antiriad).
- Symbol NULL_IS_CLEARED may be used to indicate that the memory locations
$0 and $1 in your system are zero, so they will be used for idle-looping
of audio channels (suggested by h0ffman).
- Removed cia.i and custom.i include files and included the required
symbols directly into the source.
- New function _mt_loopfx for playing looped sound effects (suggested by
mcgeezer/EAB).
- New function _mt_stopfx for immediately stopping a sound effect.
6.2:
- Fixed master volume again, which must not immediately change a channel's
volume when it is playing a sound effect (h0ffman/EAB).
- _mt_end also has to stop and reset looped sound effects. Otherwise
channels may be blocked when starting the next mod.
- Fixed a few more channel state variables, which were not reset during
_mt_end (e.g. from the funk and glissando command).
- New function mt_channelmask() to mute specific music channels at
any time (Marek Duda).
- Symbol VBLANK_MUSIC skips CIA Timer-A initialization and lets you call
_mt_music out of your own VBlank interrupt handler.
6.3:
- MINIMAL version compiles again (broken in V6.2).
- Avoid potential overflow with command 1 (portamento up).
- Muted channels by mt_channelmask() no longer touch sample pointer
and length registers (AUDxLC, AUDxLEN) (patch by roondar).
6.4:
- Fixed channel selection logic for sound effects, which was broken in
certain situations (all channels busy or looped samples) since V6.0,
and selected the worst channel instead.
- E0x command didn't work! The filter was always disabled.
- Defining NO_TIMERS disables the use of CIB-B timers and interrupts
completely. As with VBLANK_MUSIC you have to call _mt_music 50 times
per second, followed by _mt_dmaon and _mt_setrep after at least 550 ticks
each.
- Define OSCOMAPT to build a version which uses AmigaOS to register
interrupts and allocate audio channels. Patch submitted by Piru.
- Renamed mt_install_cia to mt_install and mt_remove_cia to mt_remove,
because there are now OS-compliant versions of these routines, which
additionally do other things, like allocating audio channels.
The old names remain as an alias for compatibility reasons.
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