ChannelStacker

A cross-platform desktop application for stacking and managing audio channels from multiple media files. Built with JUCE and C++20.

Features

• Drag and Drop: Drop audio or video files to automatically detect and import audio channels
• Waveform Display: Visual waveform envelope for each channel lane
• Lane Reordering: Drag lanes to reorder the channel stack
• Audio Preview: Play back all channels mixed to stereo for auditioning
• Multiple Export Options:
  • Single multichannel file (WAV, AAC, Vorbis, Opus)
  • Multiple mono files
  • Stereo pair files
  • Configurable bit depth and sample rate

Prerequisites: Installing FFmpeg

ChannelStacker requires FFmpeg to be installed on your system. The app will show a helpful dialog on first launch if FFmpeg is not detected.

macOS

Option 1: Using Homebrew (Recommended)

# Install Homebrew if you don't have it
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

# Install FFmpeg
brew install ffmpeg

Option 2: Using MacPorts

sudo port install ffmpeg

Option 3: Manual Download

1. Download a static build from FFmpeg.org
2. Extract and move ffmpeg and ffprobe to /usr/local/bin/

Windows

Option 1: Using winget

winget install ffmpeg

Option 2: Manual Download

1. Download from gyan.dev (choose "ffmpeg-release-essentials.zip")
2. Extract to C:\Program Files\ffmpeg
3. Add C:\Program Files\ffmpeg\bin to your PATH:
   • Press Win+X, select "System"
   • Click "Advanced system settings"
   • Click "Environment Variables"
   • Under "System variables", find "Path", click "Edit"
   • Click "New" and add C:\Program Files\ffmpeg\bin
   • Click "OK" on all dialogs
4. Restart any open terminals or applications

Linux

Ubuntu/Debian:

sudo apt update
sudo apt install ffmpeg

Fedora:

sudo dnf install ffmpeg

Arch Linux:

sudo pacman -S ffmpeg

Verifying Installation

After installation, verify FFmpeg is working:

ffmpeg -version
ffprobe -version

Both commands should display version information.

Building

Quick Start (macOS)

make              # Build the app
make run          # Build and run
make help         # Show all available commands

Build Steps

macOS (Recommended - using Makefile):

make                    # Build Release
make BUILD_TYPE=Debug   # Build Debug
make xcode              # Open in Xcode for debugging

macOS/Linux (manual):

mkdir build
cd build
cmake ..
cmake --build . --config Release

Windows (Visual Studio):

mkdir build
cd build
cmake .. -G "Visual Studio 17 2022"
cmake --build . --config Release

Or open the generated .sln file in Visual Studio.

Packaging and Distribution (macOS)

Create DMG Installer

# Unsigned DMG (for local testing)
make dmg-unsigned

# Signed DMG (requires Developer ID)
make sign CODESIGN_IDENTITY="Developer ID Application: Your Name (TEAMID)"
make dmg

Full Release with Notarization

For distribution outside the App Store, apps must be notarized:

# Set your Apple Developer credentials
export CODESIGN_IDENTITY="Developer ID Application: Your Name (TEAMID)"
export APPLE_ID="your@email.com"
export APPLE_TEAM_ID="XXXXXXXXXX"
export APPLE_APP_PASSWORD="@keychain:notarytool-password"

# Full release: build, sign, package, notarize
make release

Usage

1. Add Files: Drag audio or video files into the application window
2. View Channels: Each audio channel creates a lane with waveform visualization
3. Reorder: Drag the grip handle on the left of each lane to reorder
4. Delete: Click the X button on any lane to remove it
5. Export: Click "Export..." to choose an export format:
   • Single Multichannel WAV: Combines all lanes into one file with N channels
   • Multiple Mono WAVs: Exports each lane as a separate mono file
   • Stereo Pairs: Groups adjacent lanes into stereo files

Technical Notes

• Uses juce::ChildProcess to run ffmpeg/ffprobe as external commands
• Audio is decoded to raw float32 PCM for waveform computation
• Waveform envelope uses 4000 points for responsive display
• Export uses ffmpeg's asplit with pan=mono and amerge filters
• No libav* linking - pure subprocess approach for simplicity and licensing flexibility

Future Enhancements

• Batch processing