proc-tap 0.4.0

Cross-platform process-level audio capture library

📡 ProcTap

Cross-Platform Per-Process Audio Capture

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ProcTap is a Python library for per-process audio capture with platform-specific backends.

Capture audio from a specific process only — without system sounds or other app audio mixed in. Ideal for VRChat, games, DAWs, browsers, and AI audio analysis pipelines.

Platform Support

Platform	Status	Backend	Notes
Windows	✅ Fully Supported	WASAPI (C++ native)	Windows 10/11 (20H1+)
Linux	✅ Fully Supported	PipeWire Native / PulseAudio	Per-process isolation, auto-fallback (v0.3.0+)
macOS	✅ Officially Supported	ScreenCaptureKit	macOS 13+ (Ventura), bundleID-based (v0.4.0+)

_{* Linux is fully supported with PipeWire/PulseAudio (v0.3.0+). macOS is officially supported with ScreenCaptureKit (v0.4.0+).}

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🚀 Features

• 🎧 Capture audio from a single target process (VRChat, games, browsers, Discord, DAWs, streaming tools, etc.)

• 🌍 Cross-platform architecture → Windows (fully supported) | Linux (fully supported, v0.3.0+) | macOS (officially supported, v0.4.0+)

• ⚡ Platform-optimized backends → Windows: ActivateAudioInterfaceAsync (modern WASAPI) → Linux: PipeWire Native API / PulseAudio (fully supported, v0.3.0+) → macOS: ScreenCaptureKit API (macOS 13+, bundleID-based, v0.4.0+)

• 🧵 Low-latency, thread-safe audio engine → 44.1 kHz / stereo / 16-bit PCM format (Windows)

• 🐍 Python-friendly high-level API

  • Callback-based streaming
  • Async generator streaming (async for)

• 🔌 Native extensions for high-performance → C++ extension on Windows for optimal throughput

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📦 Installation

From PyPI:

pip install proc-tap

Platform-specific dependencies are automatically installed:

• Windows: No additional dependencies
• Linux: pulsectl is automatically installed, but you also need system packages:

  # Ubuntu/Debian
  sudo apt-get install pulseaudio-utils
  
  # Fedora/RHEL
  sudo dnf install pulseaudio-utils
  

Optional: High-Quality Audio Resampling (74% faster / 3.8x speedup for sample rate conversion):

pip install proc-tap[hq-resample]

Performance: With libsamplerate, resampling achieves 0.66ms per 10ms chunk (vs 2.6ms with scipy-only).

Compatibility Notes:

• ✅ Python 3.10-3.12: Works on all platforms
• ✅ Linux/macOS + Python 3.13+: Should work (you can try it!)
• ⚠️ Windows + Python 3.13+: May fail to build (as of 2025-01)
  • If it fails, the library automatically falls back to scipy's polyphase filtering
  • Still provides excellent audio quality, just 74% slower for resampling
  • You can still try installing - if it works, great! If not, no harm done.

📚 Read the Full Documentation for detailed guides and API reference.

From TestPyPI (for testing pre-releases):

pip install --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple/ proctap

From Source:

git clone https://github.com/m96-chan/ProcTap
cd ProcTap
pip install -e .

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🎬 CLI Usage (Pipe to FFmpeg)

ProcTap includes a CLI for piping audio directly to FFmpeg or other tools:

# Pipe to FFmpeg (MP3 encoding) - Direct command
proctap --pid 12345 --stdout | ffmpeg -f s16le -ar 48000 -ac 2 -i pipe:0 output.mp3

# Or using python -m
python -m proctap --pid 12345 --stdout | ffmpeg -f s16le -ar 48000 -ac 2 -i pipe:0 output.mp3

# Using process name instead of PID
proctap --name "VRChat.exe" --stdout | ffmpeg -f s16le -ar 48000 -ac 2 -i pipe:0 output.mp3

# FLAC encoding (lossless)
proctap --pid 12345 --stdout | ffmpeg -f s16le -ar 48000 -ac 2 -i pipe:0 output.flac

# Custom sample rate and mono output
proctap --pid 12345 --sample-rate 44100 --channels 1 --stdout | ffmpeg -f s16le -ar 44100 -ac 1 -i pipe:0 output.wav

CLI Options:

Option	Description
--pid PID	Process ID to capture (required if --name not used)
--name NAME	Process name to capture (e.g., VRChat.exe or VRChat)
--stdout	Output raw PCM to stdout for piping (required)
--sample-rate RATE	Sample rate in Hz (default: 48000)
--channels {1,2}	Number of channels: 1=mono, 2=stereo (default: 2)
--verbose	Enable verbose logging to stderr

Finding Process IDs:

# Windows
tasklist | findstr "VRChat"

# Linux/macOS
ps aux | grep VRChat

FFmpeg Format Arguments:

The CLI outputs raw PCM in s16le (signed 16-bit little-endian) format by default, but can be customized via --sample-rate and --channels options. FFmpeg needs these arguments:

• -f s16le: PCM format
• -ar RATE: Sample rate (must match --sample-rate, default 48000)
• -ac CHANNELS: Number of channels (must match --channels, default 2)
• -i pipe:0: Read from stdin

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🛠 Requirements

Windows (Fully Supported):

• Windows 10 / 11 (20H1 or later)
• Python 3.10+
• WASAPI support
• No admin privileges required

Linux (Fully Supported - v0.3.0+):

• Linux with PulseAudio or PipeWire
• Python 3.10+
• Auto-detection: Automatically selects best available backend
• Native PipeWire API (in development, experimental):
  • libpipewire-0.3-dev: sudo apt-get install libpipewire-0.3-dev
  • Target latency: ~2-5ms (when fully implemented)
  • Auto-selected when available (may fall back to subprocess)
• PipeWire subprocess:
  • pw-record: install with sudo apt-get install pipewire-media-session
• PulseAudio fallback:
  • pulsectl library: automatically installed
  • parec command: sudo apt-get install pulseaudio-utils
• ✅ Per-process isolation using null-sink strategy
• ✅ Graceful fallback chain: Native → PipeWire subprocess → PulseAudio

macOS (Officially Supported - v0.4.0+):

• macOS 13.0 (Ventura) or later (macOS 13+ recommended)
• Python 3.10+
• Swift helper binary (screencapture-audio)
• Screen Recording permission (automatically prompted)
• ✅ ScreenCaptureKit Backend: Apple Silicon compatible, no AMFI/SIP hacks needed
• ✅ Simple Permissions: Screen Recording only (no Microphone/TCC hacks)
• ✅ Low Latency: ~10-15ms audio capture

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🧰 Basic Usage (Callback API)

from proctap import ProcTap, StreamConfig

def on_chunk(pcm: bytes, frames: int):
    print(f"Received {len(pcm)} bytes ({frames} frames)")

pid = 12345  # Target process ID

tap = ProcTap(pid, StreamConfig(), on_data=on_chunk)
tap.start()

input("Recording... Press Enter to stop.\n")

tap.close()

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🔁 Async Usage (Async Generator)

import asyncio
from proctap import ProcTap

async def main():
    tap = ProcTap(pid=12345)
    tap.start()

    async for chunk in tap.iter_chunks():
        print(f"PCM chunk size: {len(chunk)} bytes")

asyncio.run(main())

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📄 API Overview

class ProcTap

Control Methods:

Method	Description
start()	Start WASAPI per-process capture
stop()	Stop capture
close()	Release native resources

Data Access:

Method	Description
iter_chunks()	Async generator yielding PCM chunks
read(timeout=1.0)	Synchronous: read one chunk (blocking)

Properties:

Property	Type	Description
is_running	bool	Check if capture is active
pid	int	Get target process ID
config	StreamConfig	Get stream configuration

Utility Methods:

Method	Description
set_callback(callback)	Change or remove audio callback
get_format()	Get audio format info (dict)

Audio Format

Native Backend Format (Windows WASAPI, hardcoded in C++):

Parameter	Value	Description
Sample Rate	44,100 Hz	CD quality (fixed in C++)
Channels	2	Stereo (fixed in C++)
Bit Depth	16-bit	PCM format (fixed in C++)

Output Format Conversion (v0.2.1+):

The StreamConfig class controls the output format through automatic conversion:

• Native format → converted to match your StreamConfig settings
• Supports sample rate conversion (e.g., 44.1kHz → 48kHz)
• Supports channel conversion (mono ↔ stereo)
• Supports bit depth conversion (8/16/24/32-bit)
• Zero overhead when formats match (automatic bypass)

Example:

# Get audio as 48kHz mono 24-bit
config = StreamConfig(sample_rate=48000, channels=1, width=3)
tap = ProcTap(pid, config=config)

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🎯 Use Cases

• 🎮 Record audio from one game only
• 🕶 Capture VRChat audio cleanly (without system sounds)
• 🎙 Feed high-SNR audio into AI recognition models
• 📹 Alternative to OBS "Application Audio Capture"
• 🎧 Capture DAW/app playback for analysis tools

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📚 Example: Save to WAV

from proctap import ProcTap
import wave

pid = 12345

wav = wave.open("output.wav", "wb")
wav.setnchannels(2)
wav.setsampwidth(2)  # 16-bit PCM
wav.setframerate(44100)  # Native format is 44.1 kHz

def on_data(pcm, frames):
    wav.writeframes(pcm)

with ProcTap(pid, on_data=on_data):
    input("Recording... Press Enter to stop.\n")

wav.close()

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📚 Example: Synchronous Read API

from proctap import ProcTap

tap = ProcTap(pid=12345)
tap.start()

try:
    while True:
        chunk = tap.read(timeout=1.0)  # Blocking read
        if chunk:
            print(f"Got {len(chunk)} bytes")
            # Process audio data...
        else:
            print("Timeout, no data")
except KeyboardInterrupt:
    pass
finally:
    tap.close()

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🐧 Linux Example

from proctap import ProcessAudioCapture, StreamConfig
import wave

pid = 12345  # Your target process ID

# Create WAV file
wav = wave.open("linux_capture.wav", "wb")
wav.setnchannels(2)
wav.setsampwidth(2)
wav.setframerate(44100)

def on_data(pcm, frames):
    wav.writeframes(pcm)

# Create stream config (Linux backend respects these settings)
config = StreamConfig(sample_rate=44100, channels=2)

try:
    with ProcessAudioCapture(pid, config=config, on_data=on_data):
        print("⚠️  Make sure the process is actively playing audio!")
        input("Recording... Press Enter to stop.\n")
finally:
    wav.close()

Linux-specific requirements:

• Install system package: sudo apt-get install pulseaudio-utils (provides parec command)
• Python dependency pulsectl is automatically installed with pip install proc-tap
• The target process must be actively playing audio
• See examples/linux_basic.py for a complete example

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🍎 macOS Example (v0.4.0+)

from proctap import ProcessAudioCapture, StreamConfig
import wave

pid = 12345  # Your target process ID

# Create WAV file
wav = wave.open("macos_capture.wav", "wb")
wav.setnchannels(2)
wav.setsampwidth(2)
wav.setframerate(48000)  # macOS backend default is 48 kHz

def on_data(pcm, frames):
    wav.writeframes(pcm)

# Create stream config (macOS backend respects these settings)
config = StreamConfig(sample_rate=48000, channels=2)

try:
    with ProcessAudioCapture(pid, config=config, on_data=on_data):
        print("⚠️  Make sure the process is actively playing audio!")
        print("⚠️  On first run, macOS will prompt for Screen Recording permission.")
        input("Recording... Press Enter to stop.\n")
finally:
    wav.close()

macOS-specific requirements (v0.4.0+):

• macOS 13.0 (Ventura) or later
• Swift helper binary (screencapture-audio) - automatically built during installation
• Screen Recording permission - macOS will prompt on first run
• The target process must be actively playing audio
• Works with bundleID-based capture (PID is automatically converted to bundleID)
• See examples/macos_screencapture_test.py for a complete example

Building the Swift helper manually:

cd src/proctap/swift/screencapture-audio
swift build -c release

Note: The ScreenCaptureKit backend (v0.4.0+) is recommended over the experimental PyObjC/C extension backends.

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🏗 Build From Source

git clone https://github.com/m96-chan/ProcTap
cd ProcTap
pip install -e .

Windows Build Requirements:

• Visual Studio Build Tools
• Windows SDK
• CMake (if you modularize the C++ code)

Linux:

• No C++ compiler required (pure Python)
• System dependencies: pulseaudio-utils or pipewire with libpipewire-0.3-dev

macOS:

• Swift toolchain required for building the ScreenCaptureKit helper (v0.4.0+)
• Xcode Command Line Tools: xcode-select --install
• No C++ compiler required (pure Python backend)
• Helper binary location: src/proctap/swift/screencapture-audio/

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🤝 Contributing

Contributions are welcome! We have structured issue templates to help guide your contributions:

• 🐛 Bug Report - Report bugs or unexpected behavior
• ✨ Feature Request - Suggest new features or enhancements
• ⚡ Performance Issue - Report performance problems or optimizations
• 🔧 Type Hints / Async - Improve type annotations or async functionality
• 📚 Documentation - Improve docs, examples, or guides

Special Interest:

• PRs from WASAPI/C++ experts are especially appreciated
• Linux backend improvements (PulseAudio/PipeWire per-app isolation)
• macOS backend testing (ScreenCaptureKit on macOS 13+)
• Cross-platform testing and compatibility
• Performance profiling and optimization

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📄 License

MIT License

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👤 Author

m96-chan
Windows Audio / VRChat Tools / Python / C++
https://github.com/m96-chan