Third Party Software

Third-Party Software

Flashback is built with help from several open-source projects. This page credits them and says where their licenses are in your install. Flashback's own code and branding aren't covered by these licenses.

At a glance

Component	Version	License	What Flashback uses it for
ScreenRecorderLib (Flashback fork)	6.6.0	MIT	Display capture, Media Foundation encoding and WASAPI audio, inside the capture worker
FFmpeg (Flashback LGPL build)	8.1.2	LGPL 2.1 or later	Saving, trimming, exporting and inspecting clips
Microsoft Visual C++ runtime	14.44.35211.0	Microsoft Visual Studio redistributable license terms	Runtime for the native capture engine
Velopack	1.2.0	MIT	Installer and update flow
NAudio	2.3.0	MIT	Opening the selected microphone for voice commands
sherpa-onnx	1.13.4	Apache 2.0	Offline keyword spotting for voice commands
GigaSpeech keyword-spotting model	2024-01-01 release	Apache 2.0	The small model that recognizes "Flashback clip" and the other phrases

ScreenRecorderLib

ScreenRecorderLib provides the Windows display, Media Foundation and WASAPI recording layer. Flashback ships an x64 source fork of version 6.6.0, keeping the upstream API and MIT license, with focused changes for low-overhead replay capture: frame-rate pacing, a bounded GPU sample pool, copy-engine dirty-rectangle copies, continuous output rotation on keyframes, first-frame timestamping for audio sync, discontinuity padding at the packet boundary, per-encoder textures on AMD, and several correctness fixes. Those changes are described on Capture pipeline, Hardware encoding and Audio and video sync.

FFmpeg

Flashback bundles its own FFmpeg 8.1.2 build, compiled from unmodified FFmpeg source as an LGPL-only shared build with networking off. It includes these statically linked libraries:

Library	Version	License
dav1d	1.5.4	BSD-2-Clause
OpenH264	2.6.0	BSD-2-Clause
libass	0.17.5	ISC
FreeType	2.14.3	FreeType License
HarfBuzz	14.5.0	MIT ("Old MIT")
FriBidi	1.0.17	LGPL 2.1 or later
Fontconfig	2.18.3	MIT-style
libxml2	2.16.0	MIT
libunibreak	8.0	zlib
GNU libiconv	1.19	LGPL 2.1 or later
Intel VPL dispatcher	2.17	MIT
AMD AMF headers	1.5.2.0	MIT
NVIDIA codec headers	13.0.19.2	MIT
zlib	1.3.2.1	zlib
liblzma (XZ Utils)	5.8.4	0BSD
mingw-w64 winpthreads	15.0.0	MIT
GCC runtime (libgcc, libstdc++)	16.2.0	GPL 3 with the GCC Runtime Library Exception 3.1

Portions of this software are copyright © 2026 The FreeType Project (https://freetype.org). All rights reserved.

The complete corresponding source is published in this repository's Releases under the tag ffmpeg-n8.1.2-flashback.1. Details are on FFmpeg build.

The NVIDIA, AMD and Intel hardware encoders load their runtimes from your installed graphics driver. Those runtimes aren't distributed with Flashback.

Microsoft Visual C++ runtime

The capture engine is built with the Visual C++ 2022 toolset and needs four Microsoft runtime files: vcruntime140.dll, vcruntime140_1.dll, msvcp140.dll and concrt140.dll (version 14.44.35211.0). Flashback installs the unmodified, Microsoft-signed redistributable files in its own app folder instead of asking setup to install the Visual C++ Redistributable, and replaces them with each update. They're covered by Microsoft's Visual Studio 2022 redistribution terms.

Velopack

Velopack provides the Windows installer and update mechanism. Flashback adds its own signature and package checks on top; see Update security chain.

NAudio

NAudio's WASAPI and core components open the microphone you select for optional, local voice commands.

sherpa-onnx and the GigaSpeech model

sherpa-onnx runs offline keyword spotting on your PC. The model is sherpa-onnx-kws-zipformer-gigaspeech-3.3M-2024-01-01, trained on the GigaSpeech corpus. Flashback ships only the INT8 encoder, decoder, joiner, token table and its own command list; the full-precision models, tokenizer and test audio aren't included.

Where the licenses are in your install

What	Folder in the Flashback install
ScreenRecorderLib, Velopack, NAudio, sherpa-onnx and GigaSpeech licenses	licenses
FFmpeg's static library licenses	licenses\ffmpeg
FFmpeg's own license and build record	tools\ffmpeg
The full notices file	THIRD_PARTY_NOTICES.md

Flashback installs per user under %LocalAppData%\Flashback.Desktop.

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Related pages: FFmpeg build · Architecture overview · Getting help