1 files changed, 63 insertions, 0 deletions

diff --git a/music_sampler/mixer.py b/music_sampler/mixer.py
new file mode 100644
index 0000000..9242b61
--- /dev/null
+++ b/music_sampler/mixer.py
@@ -0,0 +1,63 @@
+import sounddevice as sd
+import audioop
+import time
+
+from . import Config
+
+sample_width = Config.sample_width
+
+def sample_width_to_dtype(sample_width):
+    if sample_width == 1 or sample_width == 2 or sample_width == 4:
+        return 'int' + str(8*sample_width)
+    else:
+        raise "Unknown sample width"
+
+def _latency(latency):
+    if latency == "high" or latency == "low":
+        return latency
+    else:
+        return float(latency)
+
+class Mixer:
+    def __init__(self):
+        self.stream = sd.RawOutputStream(
+                samplerate=Config.frame_rate,
+                channels=Config.channels,
+                dtype=sample_width_to_dtype(Config.sample_width),
+                latency=_latency(Config.latency),
+                blocksize=Config.blocksize,
+                callback=self.play_callback)
+        self.open_files = []
+
+    def add_file(self, music_file):
+        if music_file not in self.open_files:
+            self.open_files.append(music_file)
+        self.start()
+
+    def remove_file(self, music_file):
+        if music_file in self.open_files:
+            self.open_files.remove(music_file)
+        if len(self.open_files) == 0:
+            self.stop()
+
+    def stop(self):
+        self.stream.stop()
+
+    def start(self):
+        self.stream.start()
+
+    def play_callback(self, out_data, frame_count, time_info, status_flags):
+        out_data_length = len(out_data)
+        empty_data = b"\0" * out_data_length
+        data = b"\0" * out_data_length
+
+        for open_file in self.open_files:
+            file_data = open_file.play_callback(out_data_length, frame_count)
+
+            if data == empty_data:
+                data = file_data
+            elif file_data != empty_data:
+                data = audioop.add(data, file_data, sample_width)
+
+        out_data[:] = data
+