From f0dcf399464f3c434c4773fba8176f03cdbae641 Mon Sep 17 00:00:00 2001
From: Michael Hansen <mike@rhasspy.org>
Date: Thu, 1 Feb 2024 16:55:14 -0600
Subject: [PATCH] Add --mic-channel-index

---
 wyoming_satellite/__main__.py  |  6 ++++++
 wyoming_satellite/satellite.py | 30 ++++++++++++++++++++++++++----
 wyoming_satellite/settings.py  |  3 +++
 3 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/wyoming_satellite/__main__.py b/wyoming_satellite/__main__.py
index 74f4289..9bcb284 100644
--- a/wyoming_satellite/__main__.py
+++ b/wyoming_satellite/__main__.py
@@ -85,6 +85,11 @@ async def main() -> None:
         action="store_true",
         help="Don't mute the microphone while awake wav is being played",
     )
+    parser.add_argument(
+        "--mic-channel-index",
+        type=int,
+        help="Take microphone input from a specific channel (first channel is 0)",
+    )
 
     # Sound output
     parser.add_argument("--snd-uri", help="URI of Wyoming sound service")
@@ -321,6 +326,7 @@ async def main() -> None:
             noise_suppression=args.mic_noise_suppression,
             seconds_to_mute_after_awake_wav=args.mic_seconds_to_mute_after_awake_wav,
             mute_during_awake_wav=(not args.mic_no_mute_during_awake_wav),
+            channel_index=args.mic_channel_index,
         ),
         vad=VadSettings(
             enabled=args.vad,
diff --git a/wyoming_satellite/satellite.py b/wyoming_satellite/satellite.py
index 492c54b..3f2a19a 100644
--- a/wyoming_satellite/satellite.py
+++ b/wyoming_satellite/satellite.py
@@ -1,4 +1,5 @@
 """Satellite code."""
+import array
 import asyncio
 import logging
 import math
@@ -458,15 +459,36 @@ class SatelliteBase:
                     continue
 
                 # Audio processing
-                if self.settings.mic.needs_processing and AudioChunk.is_type(
-                    event.type
+                if (
+                    self.settings.mic.needs_processing
+                    or (self.settings.mic.channel_index is not None)
+                    and AudioChunk.is_type(event.type)
                 ):
                     chunk = AudioChunk.from_event(event)
-                    audio_bytes = self._process_mic_audio(chunk.audio)
+                    if self.settings.mic.channel_index is not None:
+                        if chunk.width != 2:
+                            raise ValueError(
+                                "Mic channel index selection requires 16-bit samples"
+                            )
+
+                        # Convert to unsigned 16-bit array to make channel extraction easier
+                        audio_array = array.array("H", chunk.audio)
+                        audio_bytes = audio_array[
+                            self.settings.mic.channel_index :: chunk.channels
+                        ].tobytes()
+
+                    if self.settings.mic.needs_processing:
+                        if audio_bytes is None:
+                            audio_bytes = chunk.audio
+
+                        audio_bytes = self._process_mic_audio(chunk.audio)
+
                     event = AudioChunk(
                         rate=chunk.rate,
                         width=chunk.width,
-                        channels=chunk.channels,
+                        channels=chunk.channels
+                        if (self.settings.mic.channel_index is None)
+                        else 1,
                         audio=audio_bytes,
                     ).event()
                 else:
diff --git a/wyoming_satellite/settings.py b/wyoming_satellite/settings.py
index 82084d8..903ff27 100644
--- a/wyoming_satellite/settings.py
+++ b/wyoming_satellite/settings.py
@@ -55,6 +55,9 @@ class MicSettings(ServiceSettings):
     seconds_to_mute_after_awake_wav: float = 0.5
     """Extra second(s) of microphone audio to mute after awake WAV has finished playing."""
 
+    channel_index: Optional[int] = None
+    """Index of microphone channel to use. When not set, all input channels are used as-is."""
+
     @property
     def needs_webrtc(self) -> bool:
         """True if webrtc audio enhancements are needed."""