Media Devices (#493)

add new MediaDevices class to simplify interactions with local audio devices.

Author: chenosaurus

README.md

@@ -173,6 +173,98 @@ except Exception as e:
 
 You may find it useful to adjust the `response_timeout` parameter, which indicates the amount of time you will wait for a response. We recommend keeping this value as low as possible while still satisfying the constraints of your application.
 
+## Using local media devices
+
+The `MediaDevices` class provides a high-level interface for working with local audio input (microphone) and output (speakers) devices. It's built on top of the `sounddevice` library and integrates seamlessly with LiveKit's audio processing features.  In order to use `MediaDevices`, you must have the `sounddevice` library installed in your local Python environment, if it's not available, `MediaDevices` will not work.
+
+### Capturing microphone input
+
+```python
+from livekit import rtc
+
+# Create a MediaDevices instance
+devices = rtc.MediaDevices()
+
+# Open the default microphone with audio processing enabled
+mic = devices.open_input(
+    enable_aec=True,          # Acoustic Echo Cancellation
+    noise_suppression=True,   # Noise suppression
+    high_pass_filter=True,    # High-pass filter
+    auto_gain_control=True    # Automatic gain control
+)
+
+# Use the audio source to create a track and publish it
+track = rtc.LocalAudioTrack.create_audio_track("microphone", mic.source)
+await room.local_participant.publish_track(track)
+
+# Clean up when done
+await mic.aclose()
+```
+
+### Playing audio to speakers
+
+```python
+# Open the default output device
+player = devices.open_output()
+
+# Add remote audio tracks to the player (typically in a track_subscribed handler)
+@room.on("track_subscribed")
+def on_track_subscribed(track: rtc.Track, publication, participant):
+    if track.kind == rtc.TrackKind.KIND_AUDIO:
+        player.add_track(track)
+
+# Start playback (mixes all added tracks)
+await player.start()
+
+# Clean up when done
+await player.aclose()
+```
+
+### Full duplex audio (microphone + speakers)
+
+For full duplex audio with echo cancellation, open the input device first (with AEC enabled), then open the output device. The output player will automatically feed the APM's reverse stream for effective echo cancellation:
+
+```python
+devices = rtc.MediaDevices()
+
+# Open microphone with AEC
+mic = devices.open_input(enable_aec=True)
+
+# Open speakers - automatically uses the mic's APM for echo cancellation
+player = devices.open_output()
+
+# Publish microphone
+track = rtc.LocalAudioTrack.create_audio_track("mic", mic.source)
+await room.local_participant.publish_track(track)
+
+# Add remote tracks and start playback
+player.add_track(remote_audio_track)
+await player.start()
+```
+
+### Listing available devices
+
+```python
+devices = rtc.MediaDevices()
+
+# List input devices
+input_devices = devices.list_input_devices()
+for device in input_devices:
+    print(f"{device['index']}: {device['name']}")
+
+# List output devices  
+output_devices = devices.list_output_devices()
+for device in output_devices:
+    print(f"{device['index']}: {device['name']}")
+
+# Get default device indices
+default_input = devices.default_input_device()
+default_output = devices.default_output_device()
+```
+
+See [publish_mic.py](examples/local_audio/publish_mic.py) and [full_duplex.py](examples/local_audio/full_duplex.py) for complete examples.
+
+
 #### Errors
 
 LiveKit is a dynamic realtime environment and calls can fail for various reasons.

examples/local_audio/db_meter.py

@@ -0,0 +1,262 @@
+"""
+Audio dB meter utilities for LiveKit Python SDK examples.
+
+This module provides functions to calculate and display audio levels in decibels (dB)
+from raw audio samples, useful for monitoring microphone input and room audio levels.
+"""
+
+import math
+import queue
+import time
+from typing import List
+
+# dB meter configuration constants
+DB_METER_UPDATE_INTERVAL_MS = 50  # Update every 50ms
+MIC_METER_WIDTH = 25  # Width of the mic dB meter bar
+ROOM_METER_WIDTH = 25  # Width of the room dB meter bar
+
+
+def calculate_db_level(samples: List[int]) -> float:
+    """
+    Calculate decibel level from audio samples.
+
+    Args:
+        samples: List of 16-bit audio samples
+
+    Returns:
+        dB level as float. Returns -60.0 for silence/empty samples.
+    """
+    if not samples:
+        return -60.0  # Very quiet
+
+    # Calculate RMS (Root Mean Square)
+    sum_squares = sum(
+        (sample / 32767.0) ** 2  # Normalize to -1.0 to 1.0 range
+        for sample in samples
+    )
+
+    rms = math.sqrt(sum_squares / len(samples))
+
+    # Convert to dB (20 * log10(rms))
+    if rms > 0.0:
+        return 20.0 * math.log10(rms)
+    else:
+        return -60.0  # Very quiet
+
+
+def get_meter_color(db_level: float, position_ratio: float) -> str:
+    """
+    Get ANSI color code based on dB level and position in meter.
+
+    Args:
+        db_level: Current dB level
+        position_ratio: Position in meter (0.0 to 1.0)
+
+    Returns:
+        ANSI color code string
+    """
+    # Determine color based on both dB level and position in the meter
+    if db_level > -6.0 and position_ratio > 0.85:
+        return "\x1b[91m"  # Bright red - clipping/very loud
+    elif db_level > -12.0 and position_ratio > 0.7:
+        return "\x1b[31m"  # Red - loud
+    elif db_level > -18.0 and position_ratio > 0.5:
+        return "\x1b[93m"  # Bright yellow - medium-loud
+    elif db_level > -30.0 and position_ratio > 0.3:
+        return "\x1b[33m"  # Yellow - medium
+    elif position_ratio > 0.1:
+        return "\x1b[92m"  # Bright green - low-medium
+    else:
+        return "\x1b[32m"  # Green - low
+
+
+def format_single_meter(db_level: float, meter_width: int, meter_label: str) -> str:
+    """
+    Format a single dB meter with colors.
+
+    Args:
+        db_level: dB level to display
+        meter_width: Width of the meter bar in characters
+        meter_label: Label text for the meter
+
+    Returns:
+        Formatted meter string with ANSI colors
+    """
+    # ANSI color codes
+    COLOR_RESET = "\x1b[0m"
+    COLOR_DIM = "\x1b[2m"
+
+    db_clamped = max(-60.0, min(0.0, db_level))
+    normalized = (db_clamped + 60.0) / 60.0  # Normalize to 0.0-1.0
+    filled_width = int(normalized * meter_width)
+
+    meter = meter_label
+
+    # Add the dB value with appropriate color
+    if db_level > -6.0:
+        db_color = "\x1b[91m"  # Bright red
+    elif db_level > -12.0:
+        db_color = "\x1b[31m"  # Red
+    elif db_level > -24.0:
+        db_color = "\x1b[33m"  # Yellow
+    else:
+        db_color = "\x1b[32m"  # Green
+
+    meter += f"{db_color}{db_level:>7.1f}{COLOR_RESET} "
+
+    # Add the visual meter with colors
+    meter += "["
+    for i in range(meter_width):
+        position_ratio = i / meter_width
+
+        if i < filled_width:
+            color = get_meter_color(db_level, position_ratio)
+            meter += f"{color}█{COLOR_RESET}"  # Full block for active levels
+        else:
+            meter += f"{COLOR_DIM}░{COLOR_RESET}"  # Light shade for empty
+
+    meter += "]"
+    return meter
+
+
+def format_dual_meters(mic_db: float, room_db: float) -> str:
+    """
+    Format both dB meters on the same line.
+
+    Args:
+        mic_db: Microphone dB level
+        room_db: Room audio dB level
+
+    Returns:
+        Formatted dual meter string
+    """
+    mic_meter = format_single_meter(mic_db, MIC_METER_WIDTH, "Mic: ")
+    room_meter = format_single_meter(room_db, ROOM_METER_WIDTH, "  Room: ")
+
+    return f"{mic_meter}{room_meter}"
+
+
+def display_dual_db_meters(
+    mic_db_receiver, room_db_receiver, room_name: str = "Audio Levels Monitor"
+) -> None:
+    """
+    Display dual dB meters continuously until interrupted.
+
+    Args:
+        mic_db_receiver: Queue or receiver for microphone dB levels
+        room_db_receiver: Queue or receiver for room dB levels
+        room_name: Name of the room to display as the title
+    """
+    try:
+        last_update = time.time()
+        current_mic_db = -60.0
+        current_room_db = -60.0
+
+        print()  # Start on a new line
+        print(f"\x1b[92mRoom [{room_name}]\x1b[0m")
+        print(
+            "\x1b[2m────────────────────────────────────────────────────────────────────────────────\x1b[0m"
+        )
+
+        while True:
+            # Check for new data (non-blocking)
+            try:
+                while True:  # Drain all available data
+                    mic_db = mic_db_receiver.get_nowait()
+                    current_mic_db = mic_db
+            except queue.Empty:
+                pass  # No more data available
+
+            try:
+                while True:  # Drain all available data
+                    room_db = room_db_receiver.get_nowait()
+                    current_room_db = room_db
+            except queue.Empty:
+                pass  # No more data available
+
+            # Update display at regular intervals
+            current_time = time.time()
+            if current_time - last_update >= DB_METER_UPDATE_INTERVAL_MS / 1000.0:
+                # Clear current line and display meters in place
+                print(
+                    f"\r\x1b[K{format_dual_meters(current_mic_db, current_room_db)}",
+                    end="",
+                    flush=True,
+                )
+                last_update = current_time
+
+            # Small sleep to prevent busy waiting
+            time.sleep(0.01)
+
+    except KeyboardInterrupt:
+        print()  # Move to next line after Ctrl+C
+
+
+def display_single_db_meter(db_receiver, label: str = "Mic Level: ") -> None:
+    """
+    Display a single dB meter continuously until interrupted.
+
+    Args:
+        db_receiver: Queue or receiver for dB levels
+        label: Label for the meter display
+    """
+    try:
+        last_update = time.time()
+        current_db = -60.0
+        first_display = True
+
+        if first_display:
+            print()  # Start on a new line
+            print(f"\x1b[92m{label}\x1b[0m")
+            print("\x1b[2m────────────────────────────────────────\x1b[0m")
+            first_display = False
+
+        while True:
+            # Check for new data (non-blocking)
+            try:
+                while True:  # Drain all available data
+                    db_level = db_receiver.get_nowait()
+                    current_db = db_level
+            except queue.Empty:
+                pass  # No more data available
+
+            # Update display at regular intervals
+            current_time = time.time()
+            if current_time - last_update >= DB_METER_UPDATE_INTERVAL_MS / 1000.0:
+                # Clear current line and display meter in place
+                meter = format_single_meter(current_db, 40, label)
+                print(f"\r\x1b[K{meter}", end="", flush=True)
+                last_update = current_time
+
+            # Small sleep to prevent busy waiting
+            time.sleep(0.01)
+
+    except KeyboardInterrupt:
+        print()  # Move to next line after Ctrl+C
+
+
+# Example usage and testing functions
+def demo_db_meter() -> None:
+    """Demo function to test dB meter functionality."""
+    import random
+
+    # Simulate some test data
+    class MockReceiver:
+        def __init__(self):
+            self.data = []
+
+        def get_nowait(self):
+            if not self.data:
+                # Generate random dB value between -60 and 0
+                self.data.append(random.uniform(-60, 0))
+            return self.data.pop(0)
+
+    mic_receiver = MockReceiver()
+    room_receiver = MockReceiver()
+
+    print("Starting dB meter demo (Ctrl+C to stop)...")
+    display_dual_db_meters(mic_receiver, room_receiver)
+
+
+if __name__ == "__main__":
+    demo_db_meter()