4K Video Downloader was originally developed in the proprietary programming language C++ with QT framework using such libraries as boost, ffmpeg, opencv, openssl, lame, portaudio.
Fabrice Bellard, computer programmer best known as the founder of FFmpeg and QEMU
The lack of GNU C library support has not stopped various library authors from using it and bundling a replacement, among other SDL, glib2, ffmpeg, rsync...
Recording via built-in microphone or FM radio in ADPCM WAV (32 kbit/s mono or 64k bps stereo; using FFmpeg codec named adpcm ima wav), ACT (8 kbit/s) or VOR (32 or 8 kbit/s) formats, and ability to play back these files locally or via Windows Media Player when connected as an MSC device.