Implement player speed modulation opcode for triplets and such.

README.md

@@ -56,8 +56,10 @@ New features since fork
   - **Test-driven development**. Given that 4klang was already a mature project, 
     the first thing actually implemented was a set of regression tests to avoid 
     breaking everything beyond any hope of repair. Done, using CTest.
-  - **New units**. Bit-crusher, gain, inverse gain, clip. As always, if you
+  - **New units**. Bit-crusher, gain, inverse gain, clip, modulate bpm
-    don't use them, they won't be compiled into the code.
+    (proper triplets!)... As always, if you don't use them, they won't be
+    compiled into the code.
+  - **Pattern length does not have to be a power of 2**.
 
 Future goals
 ------------
@@ -66,8 +68,8 @@ Future goals
     on CMake and compiles on Windows. Cross-platform NASM/YASM macros have been
     drafted and remain to be tested. Once the project is more mature, I will 
     try compiling on other platforms.
-  - **Even more opcodes**. At least: compressor (with side-chaining), change
+  - **Even more opcodes**. At least: compressor (with side-chaining). Maybe 
-    bpm. Maybe also equalizer.
+    also equalizer.
   - **Support for 64-bit targets**.
   - **Browser-based GUI and MIDI instrument**. Modern browsers support WebMIDI,
      WebAudio and, most importantly, they are cross-platform and come installed

src/opcodes/flowcontrol.asm

@@ -49,6 +49,33 @@ EXPORT MANGLE_FUNC(su_op_advance,0)     ; Stack: addr voice wrkptr valptr comptr
 
 %endif
 
+;-------------------------------------------------------------------------------
+;   SPEED tick
+;-------------------------------------------------------------------------------
+%if SPEED_ID > -1
+
+SECT_TEXT(suspeed)
+
+EXPORT MANGLE_FUNC(su_op_speed,0)
+    fsub    dword [c_0_5]                ; s-.5
+    fadd    st0, st0                     ; 2*s-1
+    fmul    dword [c_bpmscale]           ; (2*s-1)*64/24, let's call this p from now on
+    call    MANGLE_FUNC(su_power,0)      ; 2^p, this is how many ticks we should be taking
+    fld1                                 ; 1 2^p
+    fsubp   st1, st0                     ; 2^p-1, the player is advancing 1 tick by its own
+    fadd    dword [WRK+su_speed_wrk.remainder] ; t+2^p-1, t is the remainder from previous rounds as ticks have to be rounded to 1
+    push    eax
+    fist    dword [esp]                  ; Main stack: k=int(t+2^p-1)
+    fisub   dword [esp]                  ; t+2^p-1-k, the remainder
+    pop     eax
+    add     dword [esp+24], eax          ; add the whole ticks to song tick count, [esp+24] is the current tick in the row
+    fstp    dword [WRK+su_speed_wrk.remainder] ; save the remainder for future
+    ret
+
+SECT_DATA(suconst)
+    c_bpmscale      dd      2.666666666666 ; 64/24, 24 values will be double speed, so you can go from ~ 1/2.5 speed to 2.5x speed
+
+%endif
 
 ;-------------------------------------------------------------------------------
 ;    Constants

src/opcodes/flowcontrol.inc

@@ -0,0 +1,21 @@
+;-------------------------------------------------------------------------------
+;   SPEED related defines
+;-------------------------------------------------------------------------------
+%assign SPEED_ID -1
+%macro USE_SPEED 0
+    %if SPEED_ID == -1
+        %assign SPEED_ID CUR_ID
+        %assign CUR_ID CUR_ID + 2
+        %xdefine OPCODES OPCODES MANGLE_FUNC(su_op_speed,0),
+        %xdefine NUMPARAMS NUMPARAMS 0,
+    %endif
+%endmacro
+
+%macro SU_SPEED 0
+    USE_SPEED
+    %xdefine CMDS CMDS SPEED_ID, ; there is no stereo variant I can think of
+%endmacro
+
+struc su_speed_wrk
+    .remainder      resd    1
+endstruc

src/sointu.inc

@@ -127,6 +127,7 @@
 %define MONO            0
 %define STEREO          1
 
+%include "opcodes/flowcontrol.inc"
 %include "opcodes/arithmetic.inc"
 %include "opcodes/effects.inc"
 %include "opcodes/sources.inc"

tests/CMakeLists.txt

@@ -123,3 +123,4 @@ target_compile_definitions(test_envelope_16bit PUBLIC SU_USE_16BIT_OUTPUT)
 
 regression_test(test_polyphony "ENVELOPE;VCO_SINE")
 regression_test(test_chords "ENVELOPE;VCO_SINE")
+regression_test(test_speed "ENVELOPE;VCO_SINE")

tests/test_speed.asm

@@ -0,0 +1,37 @@
+%define BPM 100
+%define USE_SECTIONS
+
+%include "../src/sointu.inc"
+
+; warning: crashes ahead. Now that the bpm could be changed and even modulated by other
+; signals, there is no easy way to figure out how many ticks your song is. Either
+; allocate some extra memory of the output just in case or simulate exactly how many
+; samples are outputted. Here the triplets are slightly faster than the original so 
+; they fit the default MAX_TICKS that is calculated using the simple bpm assumption.
+SU_BEGIN_PATTERNS
+    PATTERN 64, 0, 64, 64, 64,  0, 64, 64, 64, 0, 64, 64,   65, 0, 65, 65,
+    PATTERN 64, 0,  0,  0,  0,  0,  0,  0,  0, 0,  0,  0,    0, 0,  0,  0, ; 4-rows
+    PATTERN 78, 0, 54,  0, 78,  0, 54,  0, 78, 0, 54,  0,   78, 0, 54,  0, ; triplets
+SU_END_PATTERNS
+
+SU_BEGIN_TRACKS
+    TRACK   VOICES(1),0,0
+    TRACK   VOICES(1),1,2
+SU_END_TRACKS
+
+SU_BEGIN_PATCH
+    SU_BEGIN_INSTRUMENT VOICES(1) ; Instrument0
+        SU_ENVELOPE MONO,ATTAC(64),DECAY(64),SUSTAIN(0),RELEASE(64),GAIN(128)
+        SU_ENVELOPE MONO,ATTAC(64),DECAY(64),SUSTAIN(0),RELEASE(64),GAIN(128)
+        SU_OSCILLAT MONO,TRANSPOSE(64),DETUNE(32),PHASE(0),COLOR(96),SHAPE(64),GAIN(128), FLAGS(TRISAW)
+        SU_OSCILLAT MONO,TRANSPOSE(72),DETUNE(64),PHASE(64),COLOR(64),SHAPE(96),GAIN(128), FLAGS(TRISAW)
+        SU_MULP     STEREO
+        SU_OUT      STEREO,GAIN(128)
+    SU_END_INSTRUMENT
+    SU_BEGIN_INSTRUMENT VOICES(1) ; Speed changer
+        SU_LOADNOTE MONO
+        SU_SPEED
+    SU_END_INSTRUMENT
+SU_END_PATCH
+
+%include "../src/sointu.asm"