Add .wav to pcm converter.

1 files changed, 121 insertions, 0 deletions

diff --git a/pokemontools/pcm.py b/pokemontools/pcm.py
new file mode 100755
index 0000000..b352147
--- /dev/null
+++ b/pokemontools/pcm.py
@@ -0,0 +1,121 @@
+# pcm.py
+# Converts between .wav files and 1-bit pcm data. (pcm = pulse-code modulation)
+
+import argparse
+import os
+import struct
+import wave
+
+
+def convert_to_wav(filenames=[]):
+    """
+    Converts a file containing 1-bit pcm data into a .wav file.
+    """
+    for filename in filenames:
+        with open(filename, 'rb') as pcm_file:
+            # Generate array of on/off pcm values.
+            samples = []
+            byte = pcm_file.read(1)
+            while byte != "":
+                byte = struct.unpack('B', byte)[0]
+                for i in range(8):
+                    bit_index = 7 - i
+                    value = (byte >> bit_index) & 1
+                    samples.append(value)
+                byte = pcm_file.read(1)
+
+        # Write a .wav file using the pcm data.
+        name, extension = os.path.splitext(filename)
+        wav_filename = name + '.wav'
+        wave_file = wave.open(wav_filename, 'w')
+        wave_file.setframerate(22050)
+        wave_file.setnchannels(1)
+        wave_file.setsampwidth(1)
+
+        for value in samples:
+            if value > 0:
+                value = 0xff
+
+            packed_value = struct.pack('B', value)
+            wave_file.writeframesraw(packed_value)
+
+        wave_file.close()
+
+
+def convert_to_pcm(filenames=[]):
+    """
+    Converts a .wav file into 1-bit pcm data.
+    Samples in the .wav file are simply clamped to on/off.
+
+    TODO: This currently only works correctly on .wav files with the following attributes:
+            1. Sample Rate = 22050
+            2. Sample Width = 1 byte
+            3. 1 Channel
+        It can be improved to account for these factors.
+    """
+    for filename in filenames:
+        samples, sample_width = get_wav_samples(filename)
+        sample_middle = (sample_width * 0xff) / 2
+
+        # Generate a list of clamped samples
+        clamped_samples = []
+        for sample in samples:
+            # Clamp the raw sample to on/off
+            if sample < sample_middle:
+                clamped_samples.append(0)
+            else:
+                clamped_samples.append(1)
+
+        # The pcm data must be a multiple of 8, so pad the clamped samples with 0.
+        while len(clamped_samples) % 8 != 0:
+            clamped_samples.append(0)
+
+        # Pack the 1-bit samples together.
+        packed_samples = bytearray()
+        for i in xrange(0, len(clamped_samples), 8):
+            # Read 8 pcm values to pack one byte.
+            packed_value = 0
+            for j in range(8):
+                packed_value <<= 1
+                packed_value += clamped_samples[i + j]
+            packed_samples.append(packed_value)
+
+        # Open the output .pcm file, and write all 1-bit samples.
+        name, extension = os.path.splitext(filename)
+        pcm_filename = name + '.pcm'
+        with open(pcm_filename, 'wb') as out_file:
+            out_file.write(packed_samples)
+
+
+def get_wav_samples(filename):
+    """
+    Reads the given .wav file and returns a list of its raw samples.
+    Also returns the byte width of the samples.
+    """
+    wav_file = wave.open(filename, 'r')
+    sample_width = wav_file.getsampwidth()
+    sample_count = wav_file.getnframes()
+
+    samples = bytearray(wav_file.readframes(sample_count))
+
+    return samples, sample_width
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument('mode')
+    ap.add_argument('filenames', nargs='*')
+    args = ap.parse_args()
+
+    method = {
+        'wav': convert_to_wav,
+        'pcm': convert_to_pcm,
+    }.get(args.mode, None)
+
+    if method == None:
+        raise Exception, "Unknown conversion method!"
+
+    method(args.filenames)
+
+if __name__ == "__main__":
+    main()