Loopback Capture

What is Loopback Capture

Loopback Capture is a tool which can be used to capture the loopback from audio devices.

Build (Windows)

The win32\csharp and win32\dll version require some packages, before you build it, you need to install these packages and put dll files to 3rdparty folder:

• CSCore - An advanced audio library, written in C#.
• Unmanaged Exports - DllExport for .Net.

Suggest to use NuGet to install them:

nuget install .\build\packages.config

Then in MSBuild Command Prompt:

> build.all.bat
or
> build.cpp.bat
or
> build.csharp.bat
or
> build.dll.bat

Install Soundflower (macOS)

macOS not support to capture Loopback from device directly. The workaround is to route what is playing on the computer digitally back to the input without using a cable.

Soundflower is a free open source system add-on for Mac computers that allows you to route what is playing on the computer digitally back to the input without using a cable. Set Soundflower as your system output device, then in Audacity, set Soundflower as your recording device.

You can get compiled Soundflower kernel extension in here: https://github.com/mattingalls/Soundflower/releases

About how to setup device, there is an example in Release Note please take a look.

Install Avconv Tool (Linux)

avconv is a part from "libav-tools" package which is support to record audio use command line with specific format specific duration and from specific device.

sudo apt-get install libav-tools

BTW, the pulsectl is required for linux\LoopbackCapture.py, use following command to install it:

pip install pulsectl

Usage

# CSharp

> LoopbackCapture.exe <output/wav> <time/milliseconds>

# C++

> LoopbackCapture.exe -?
> LoopbackCapture.exe --list-devices
> LoopbackCapture.exe [--device "Device long name"] [--file "file name"] [--time "capture milliseconds"] [--int-16]
    -? prints this message.
    --list-devices displays the long names of all active playback devices.
    --device captures from the specified device (default if omitted)
    --file saves the output to a file
    --time capture specific milliseconds
    --int-16 attempts to coerce data to 16-bit integer format

# Python (DLL)

> import os, sys, platform, clr
> if platform.architecture()[0] == "32bit":
>     DLL_PATH = r"bin\x86\Release"
> elif platform.architecture()[0] == "64bit":
>     DLL_PATH = r"bin\x64\Release"
> DLL_PATH = os.path.join(os.path.dirname(os.path.realpath(__file__)), DLL_PATH)
> sys.path.append(DLL_PATH)
> clr.AddReference("LoopbackCapture")
> from LoopbackCapture import LoopbackCapture
> lc = LoopbackCapture()
> lc.Capture("record.wav", 15000)

# Python (macOS)

> from mac.LoopbackCapture import record_sounds
> exit_code = record_sounds(audio_file, milliseconds)

# Python (Linux)

> from linux.LoopbackCapture import record_sounds
> exit_code = record_sounds(audio_file, milliseconds)