# Riff: sound and licensing

## Where are the equalizer and sound effects?

There is no built-in equalizer, and the author does not plan to add one. His preference is to tune
the audio chain with a system DSP such as [JamesDSP](https://james34602.github.io/JamesDSPManager/)
or a separate DSP processor/amplifier. Whether a system tool fits your head unit depends on its
firmware and output path.

Riff does include ReplayGain and a peak limiter, so neighboring recordings do not make you keep
reaching for the volume control. On Android, Riff does that work on the audio samples itself.

## What do ReplayGain F, I and N mean?

**F** outputs float32 after processing; **I** outputs int16; **N** has no Riff ReplayGain processor.
In I/F, the processor starts with PCM16, applies the gain and runs a peak limiter. F avoids rounding
the result back to int16. If F causes trouble on a particular device, try I; that is a fallback
worth checking, not a guarantee for every firmware.

Open **Settings → More… → ReplayGain**, choose the values and save **More**.

## What are the numbers 16, 18, 23 and 0?

Target loudness: 16 means -16 LUFS, 18 means -18 LUFS, and 23 means -23 LUFS. The current starting
setting is **F / 23**. This concerns the recording's overall loudness, not forcing every instant of
a song to the same level.

**0** applies no ReplayGain adjustment, but I/F still run the limiter. Use **N** to remove Riff's
processor. Missing usable gain data does not become an invented adjustment from the target alone.

## Where does ReplayGain come from? Should I prepare my files first?

That is a good way to get a whole-recording scan before copying files to the drive.
[rsgain](https://github.com/complexlogic/rsgain) and
[loudgain](https://github.com/Moonbase59/loudgain) can write ReplayGain metadata without rewriting
the audio itself. Riff also reads supported iTunes/Apple Music Sound Check data, `iTunNORM`.

Without usable data, Riff attempts its own measurement. Normally it uses three up-to-20-second
sections, up to a minute in total. If the bounded measurements fail, music can get a full-span
fallback; audiobooks do not. A hard “never more than one minute” limit would be inaccurate.

## Does float output make this a bit-perfect player?

No. I/F start with PCM16 even if the source stores more bits. Float output cannot recover precision
already lost at the input. Riff concentrates on listening comfortably in a car.

A dedicated bit-perfect USB path is a different job. For example,
[Resonāda](https://gitlab.com/resonada/resonada/-/blob/main/README.md) advertises that sort of
capability; check your actual hardware and output before assuming it will work.

## Is Riff free, and do donations unlock features?

First-party code is open under GPL-3.0-or-later. Donations do not unlock features or restrict code
access or use. Local listening needs no account or streaming subscription. GPL allows third-party
distributors to charge for their builds.

## What does GPLv3 mean for me?

You can use, study, change and share the code. Making a private modification alone does not require
you to publish it, and the licence does not take ownership of your music.

If you distribute a copy, keep the required notices and licence and supply the corresponding source
in a permitted way. Third-party components keep their own terms. The
[GNU GPL FAQ](https://www.gnu.org/licenses/gpl-faq.en.html) and
[licence text](https://www.gnu.org/licenses/gpl-3.0.html) have the details.

## May I sell it, bundle it in head-unit firmware or distribute it through a store?

Yes, with the GPL obligations still attached. Recipients keep their GPL rights; covered modified
code cannot simply become closed source. Where GPLv3's User Product rules apply, the required
installation information matters too. Check store/firmware conditions, dependencies and the
repository notices before distributing. GNU's
[GPLv3 guide](https://www.gnu.org/licenses/quick-guide-gplv3.html) explains that part.

## Does GPLv3 promise support or make this pre-release build risk-free?

No. An open-source licence is not a promise that every device works or that lost state can always be
recovered. This is still an unfinished pre-release project.