what is equalizer fr?

This is a terminal-based audio equalizer that adjusts sound in real time as it plays. It takes raw, uncompressed audio coming in through standard input, a named pipe called a FIFO, or a unix socket, runs it through the same digital signal processing used by the Rockbox media player firmware, and then either plays the adjusted sound through your speakers or passes it along to another program. The equalizer gives you 10 separate frequency bands to adjust, plus dedicated bass and treble controls, each adjustable up or down by 24 decibels. All of this is controlled through a visual interface in your terminal with sliders for every band, a status line showing details like sample rate and playback time, and a bar showing which keys do what. Any change you make is saved automatically to a settings file and reloaded the next time you run the program, and there are ready-made presets for genres like rock, jazz, and electronic, plus bass-boost and treble-boost options. It accepts many different raw audio formats and sample rates, automatically converting them to match your sound card, and works with mono, stereo, or multichannel audio. Instead of playing through speakers, it can also work as a pure filter, taking audio in and sending processed audio back out through a pipe or socket, so it can sit in the middle of a chain of other audio tools like ffmpeg or a Spotify client called spotifyd. Installation is available through Homebrew on macOS and Linux, prebuilt Debian and Fedora packages, downloadable tarballs, Nix, or building from source with Rust's cargo tool, though building from source needs a C compiler and, on Linux, some audio development libraries installed first. There is also a remote control feature using a gRPC API, letting you adjust the equalizer running on one machine from another.