Added pitch shifting to audio_sdl2

examples/audio/pitch.py

@@ -0,0 +1,42 @@
+# encoding: utf8
+
+from kivy.app import App
+from kivy.lang import Builder
+from kivy.clock import Clock
+from kivy.core.audio import SoundLoader
+from kivy.uix.boxlayout import BoxLayout
+from kivy.uix.button import Button
+
+from sys import version_info
+
+
+NOTES = (
+    ('Do',  1),
+    ('Ré',  9/8.),
+    ('Mi',  5/4.),
+    ('Fa',  4/3.),
+    ('Sol', 3/2.),
+    ('La',  5/3.),
+    ('Si',  15/8.),
+)
+
+class Test(App):
+    def build(self):
+        self.sound = SoundLoader.load(
+            '/usr/lib64/python{}.{}/test/audiodata/pluck-pcm32.wav'
+            .format(*version_info[0:2])
+        )
+        root = BoxLayout()
+        for octave in range(-2, 3):
+            for note, pitch in NOTES:
+                button = Button(text=note)
+                button.pitch = pitch * 2 ** octave
+                button.bind(on_release=self.play_note)
+                root.add_widget(button)
+        return root
+
+    def play_note(self, button):
+        self.sound.pitch = button.pitch
+        self.sound.play()
+
+Test().run()

kivy/core/audio/__init__.py

@@ -50,10 +50,12 @@
 from kivy.compat import PY2
 from kivy.resources import resource_find
 from kivy.properties import StringProperty, NumericProperty, OptionProperty, \
-    AliasProperty, BooleanProperty
+    AliasProperty, BooleanProperty, BoundedNumericProperty
 from kivy.utils import platform
 from kivy.setupconfig import USE_SDL2
 
+from sys import float_info
+
 
 class SoundLoader:
     '''Load a sound, using the best loader for the given file type.
@@ -116,6 +118,16 @@ class Sound(EventDispatcher):
     to 1.
     '''
 
+    pitch = BoundedNumericProperty(1., min=float_info.epsilon)
+    '''Pitch of a sound. 2 is an octave higher, .5 one below. This is only
+    implemented for SDL2 audio provider yet.
+
+    .. versionadded:: 1.9.2
+
+    :attr:`pitch` is a :class:`~kivy.properties.NumericProperty` and defaults
+    to 1.
+    '''
+
     state = OptionProperty('stop', options=('stop', 'play'))
     '''State of the sound, one of 'stop' or 'play'.
 

kivy/core/audio/audio_sdl2.pyx

@@ -28,6 +28,7 @@ Depending the compilation of SDL2 mixer and/or installed libraries:
 __all__ = ('SoundSDL2', 'MusicSDL2')
 
 include "../../../kivy/lib/sdl2.pxi"
+include "../../../kivy/graphics/common.pxi"  # For malloc and memcpy (on_pitch)
 
 from kivy.core.audio import Sound, SoundLoader
 from kivy.logger import Logger
@@ -36,11 +37,6 @@ from kivy.clock import Clock
 cdef int mix_is_init = 0
 cdef int mix_flags = 0
 
-# old code from audio_sdl, never used it = unfinished?
-#cdef void channel_finished_cb(int channel) nogil:
-#    with gil:
-#        print('Channel finished playing.', channel)
-
 
 cdef mix_init():
     cdef int audio_rate = 44100
@@ -72,14 +68,13 @@ cdef mix_init():
         mix_is_init = -1
         return 0
 
-    #Mix_ChannelFinished(channel_finished_cb)
-
     mix_is_init = 1
     return 1
 
 # Container for samples (Mix_LoadWAV)
 cdef class ChunkContainer:
     cdef Mix_Chunk *chunk
+    cdef Mix_Chunk *original_chunk
     cdef int channel
 
     def __init__(self):
@@ -92,6 +87,9 @@ cdef class ChunkContainer:
                 Mix_HaltChannel(self.channel)
             Mix_FreeChunk(self.chunk)
             self.chunk = NULL
+        if self.original_chunk != NULL:
+            Mix_FreeChunk(self.original_chunk)
+            self.original_chunk = NULL
 
 # Container for music (Mix_LoadMUS), one channel only
 cdef class MusicContainer:
@@ -158,6 +156,26 @@ class SoundSDL2(Sound):
         frames = points / channels
         return <double>frames / <double>freq
 
+    def on_pitch(self, instance, value):
+        cdef ChunkContainer cc = self.cc
+        cdef int freq, channels
+        cdef unsigned short fmt
+        cdef SDL_AudioCVT cvt
+        if cc.chunk == NULL:
+            return
+        if not Mix_QuerySpec(&freq, &fmt, &channels):
+            return
+        SDL_BuildAudioCVT(
+            &cvt,
+            fmt, channels, int(freq * self.pitch),
+            fmt, channels, freq,
+        )
+        cvt.buf = <Uint8 *>malloc(cc.original_chunk.alen * cvt.len_mult)
+        cvt.len = cc.original_chunk.alen
+        memcpy(cvt.buf, cc.original_chunk.abuf, cc.original_chunk.alen)
+        SDL_ConvertAudio(&cvt)
+        cc.chunk = Mix_QuickLoad_RAW(cvt.buf, <Uint32>(cvt.len * cvt.len_ratio))
+
     def play(self):
         cdef ChunkContainer cc = self.cc
         self.stop()
@@ -201,7 +219,10 @@ class SoundSDL2(Sound):
             Logger.warning('AudioSDL2: Unable to load {}: {}'.format(
                            self.filename, Mix_GetError()))
         else:
+            cc.original_chunk = Mix_QuickLoad_RAW(cc.chunk.abuf, cc.chunk.alen)
             cc.chunk.volume = int(self.volume * 128)
+            if self.pitch != 1.:
+                self.on_pitch(self, self.pitch)
 
     def unload(self):
         cdef ChunkContainer cc = self.cc

kivy/lib/sdl2.pxi

@@ -775,6 +775,30 @@ cdef extern from "SDL_ttf.h":
 
 cdef extern from "SDL_audio.h":
     cdef int AUDIO_S16SYS
+    ctypedef struct SDL_AudioFilter:
+        pass
+    ctypedef struct SDL_AudioCVT:
+        int needed
+        int src_format
+        int dst_format
+        double rate_incr
+        Uint8 *buf
+        int len
+        int len_cvt
+        int len_mult
+        double len_ratio
+        SDL_AudioFilter filters[10]
+        int filter_index
+    cdef int SDL_BuildAudioCVT(
+        SDL_AudioCVT *cvt,
+        int src_format,
+        Uint8 src_channels,
+        int src_rate,
+        int dst_format,
+        Uint8 dst_channels,
+        int dst_rate
+    )
+    cdef int SDL_ConvertAudio(SDL_AudioCVT *cvt)
 
 cdef extern from "SDL_mixer.h":
     cdef struct Mix_Chunk: