1 files changed, 123 insertions, 0 deletions
diff --git a/display/puremixer.py b/display/puremixer.py
new file mode 100644
index 0000000..d0b567a
--- /dev/null
+++ b/display/puremixer.py
@@ -0,0 +1,123 @@
+import sys, audioop
+
+
+class PureMixer:
+    #
+    #  An audio mixer in Python based on audioop
+    #
+    #  Note that opening the audio device itself is outside the scope of
+    #  this module.  Anything else could also be done with the mixed data,
+    #  e.g. stored on disk, for all this module knows.
+
+    def __init__(self, freq=44100, bits=8, signed=0,
+                       channels=1, byteorder=None):
+        """Open the mixer and set its parameters."""
+        self.freq = freq
+        self.bytes = bits/8
+        self.signed = signed
+        self.channels = channels
+        self.byteorder = byteorder or sys.byteorder
+        self.parameters = (freq, self.bytes, signed, channels, self.byteorder)
+        self.bytespersample = channels*self.bytes
+        self.queue = '\x00' * self.bytes
+
+    def resample(self, data, freq=44100, bits=8, signed=0,
+                             channels=1, byteorder=None):
+        "Convert a sample to the mixer's own format."
+        bytes = bits/8
+        byteorder = byteorder or sys.byteorder
+        if (freq, bytes, signed, channels, byteorder) == self.parameters:
+            return data
+        # convert to native endianness
+        if byteorder != sys.byteorder:
+            data = byteswap(data, bytes)
+            byteorder = sys.byteorder
+        # convert unsigned -> signed for the next operations
+        if not signed:
+            data = audioop.bias(data, bytes, -(1<<(bytes*8-1)))
+            signed = 1
+        # convert stereo -> mono
+        while channels > self.channels:
+            assert channels % 2 == 0
+            data = audioop.tomono(data, bytes, 0.5, 0.5)
+            channels /= 2
+        # resample to self.freq
+        if freq != self.freq:
+            data, ignored = audioop.ratecv(data, bytes, channels,
+                                           freq, self.freq, None)
+            freq = self.freq
+        # convert between 8bits and 16bits
+        if bytes != self.bytes:
+            data = audioop.lin2lin(data, bytes, self.bytes)
+            bytes = self.bytes
+        # convert mono -> stereo
+        while channels < self.channels:
+            data = audioop.tostereo(data, bytes, 1.0, 1.0)
+            channels *= 2
+        # convert signed -> unsigned
+        if not self.signed:
+            data = audioop.bias(data, bytes, 1<<(bytes*8-1))
+            signed = 0
+        # convert to mixer endianness
+        if byteorder != self.byteorder:
+            data = byteswap(data, bytes)
+            byteorder = self.byteorder
+        # done
+        if (freq, bytes, signed, channels, byteorder) != self.parameters:
+            raise ValueError, 'sound sample conversion failed'
+        return data
+
+    def wavesample(self, file):
+        "Read a sample from a .wav file (or file-like object)."
+        import wave
+        w = wave.open(file, 'r')
+        return self.resample(w.readframes(w.getnframes()),
+                             freq = w.getframerate(),
+                             bits = w.getsampwidth() * 8,
+                             signed = w.getsampwidth() > 1,
+                             channels = w.getnchannels(),
+                             byteorder = 'little')
+
+    def mix(self, mixer_channels, bufsize):
+        """Mix the next batch buffer.
+        Each object in the mixer_channels list must be a file-like object
+        with a 'read(size)' method."""
+        data = ''
+        already_seen = {}
+        channels = mixer_channels[:]
+        channels.reverse()
+        for c in channels:
+            if already_seen.has_key(c):
+                data1 = ''
+            else:
+                data1 = c.read(bufsize)
+                already_seen[c] = 1
+            if data1:
+                l = min(len(data), len(data1))
+                data = (audioop.add(data[:l], data1[:l], 1) +
+                        (data1[l:] or data[l:]))
+            else:
+                try:
+                    mixer_channels.remove(c)
+                except ValueError:
+                    pass
+        data += self.queue * ((bufsize - len(data)) / self.bytes)
+        self.queue = data[-self.bytes:]
+        return data
+
+
+def byteswap(data, byte):
+    if byte == 1:
+        return
+    if byte == 2:
+        typecode = 'h'
+    elif byte == 4:
+        typecode = 'i'
+    else:
+        raise ValueError, 'cannot convert endianness for samples of %d bytes' % byte
+    import array
+    a = array.array(typecode, data)
+    if a.itemsize != byte:
+        raise ValueError, 'endianness convertion failed'
+    a.byteswap()
+    return a.tostring()