Add ability to set bandwith and bitrate.

Patch by Jake.

discord/opus.py

@@ -49,6 +49,7 @@ exported_functions = [
     ('opus_encoder_get_size', [ctypes.c_int], ctypes.c_int),
     ('opus_encoder_create', [ctypes.c_int, ctypes.c_int, ctypes.c_int, c_int_ptr], EncoderStructPtr),
     ('opus_encode', [EncoderStructPtr, c_int16_ptr, ctypes.c_int, ctypes.c_char_p, ctypes.c_int32], ctypes.c_int32),
+    ('opus_encoder_ctl', None, ctypes.c_int32),
     ('opus_encoder_destroy', [EncoderStructPtr], None)
 ]
 
@@ -64,7 +65,9 @@ def libopus_loader(name):
             raise e
 
         try:
-            func.argtypes = item[1]
+            if item[1]:
+                func.argtypes = item[1]
+
             func.restype = item[2]
         except KeyError:
             pass
@@ -134,6 +137,7 @@ class OpusError(DiscordException):
     code : int
         The error code returned.
     """
+
     def __init__(self, code):
         self.code = code
         msg = _lib.opus_strerror(self.code).decode('utf-8')
@@ -150,6 +154,16 @@ OK = 0
 APPLICATION_AUDIO    = 2049
 APPLICATION_VOIP     = 2048
 APPLICATION_LOWDELAY = 2051
+CTL_SET_BITRATE      = 4002
+CTL_SET_BANDWIDTH    = 4008
+
+band_ctl = {
+    'narrow': 1101,
+    'medium': 1102,
+    'wide': 1103,
+    'superwide': 1104,
+    'full': 1105,
+}
 
 class Encoder:
     def __init__(self, sampling, channels, application=APPLICATION_AUDIO):
@@ -158,7 +172,7 @@ class Encoder:
         self.application = application
 
         self.frame_length = 20
-        self.sample_size = 2 * self.channels # (bit_rate / 8) but bit_rate == 16
+        self.sample_size = 2 * self.channels  # (bit_rate / 8) but bit_rate == 16
         self.samples_per_frame = int(self.sampling_rate / 1000 * self.frame_length)
         self.frame_size = self.samples_per_frame * self.sample_size
 
@@ -166,6 +180,8 @@ class Encoder:
             raise OpusNotLoaded()
 
         self._state = self._create_state()
+        self.set_bitrate(128)
+        self.set_bandwidth('full')
 
     def __del__(self):
         if hasattr(self, '_state'):
@@ -182,6 +198,27 @@ class Encoder:
 
         return result
 
+    def set_bitrate(self, kbps):
+        kbps = min(128, max(16, int(kbps)))
+
+        ret = _lib.opus_encoder_ctl(self._state, CTL_SET_BITRATE, kbps * 1024)
+        if ret < 0:
+            log.info('error has happened in set_bitrate')
+            raise OpusError(ret)
+
+        return kbps
+
+    def set_bandwidth(self, req):
+        if req not in band_ctl:
+            raise KeyError('%r is not a valid bandwidth setting. Try one of: %s' % (req, ','.join(band_ctl)))
+
+        k = band_ctl[req]
+        ret = _lib.opus_encoder_ctl(self._state, CTL_SET_BANDWIDTH, k)
+
+        if ret < 0:
+            log.info('error has happened in set_bandwidth')
+            raise OpusError(ret)
+
     def encode(self, pcm, frame_size):
         max_data_bytes = len(pcm)
         pcm = ctypes.cast(pcm, c_int16_ptr)