Typescript FLP Library

A minimalist TypeScript library for reading and modifying FL Studio project files (.flp).

Designed for non-destructive modifications ("conservative patch").

Features

• Project metadata: Read and modify name, description, artist, genre, and BPM
• Time information: Read and modify creation date and work time
• Samples: List sample paths and batch rewrite paths
• VST Plugins: List plugins with name and vendor (when available)
• Stable round-trip: Untargeted data remains byte-for-byte identical

Installation

npm install ts-flp
# or
pnpm add ts-flp
# or
yarn add ts-flp

Usage

Reading a project

import { readFileSync, writeFileSync } from 'fs';
import { parseFlp, serializeFlp, readProjectMeta, listSamples, listPlugins } from 'ts-flp';

// Load and parse the .flp file
const buffer = readFileSync('my-project.flp');
const parsed = parseFlp(buffer);

// Read metadata
const meta = readProjectMeta(parsed);
console.log(`Project: ${meta.name}`);
console.log(`Artist: ${meta.artist}`);
console.log(`Genre: ${meta.genre}`);
console.log(`BPM: ${meta.bpm}`);

// List samples
const samples = listSamples(parsed);
for (const sample of samples) {
  console.log(`Sample: ${sample.path}`);
}

// List plugins
const plugins = listPlugins(parsed);
for (const plugin of plugins) {
  console.log(`Plugin: ${plugin.name} (${plugin.vendor ?? 'N/A'})`);
}

Modifying metadata

import { readFileSync, writeFileSync } from 'fs';
import { parseFlp, serializeFlp, writeProjectMeta } from 'ts-flp';

const buffer = readFileSync('my-project.flp');
let parsed = parseFlp(buffer);

// Modify metadata
parsed = writeProjectMeta(parsed, {
  name: 'New Title',
  artist: 'My Name',
  genre: 'Electronic',
  bpm: 140,
});

// Save
writeFileSync('my-project-modified.flp', serializeFlp(parsed));

Rewriting sample paths

import { readFileSync, writeFileSync } from 'fs';
import { parseFlp, serializeFlp, rewriteSamplePaths } from 'ts-flp';

const buffer = readFileSync('my-project.flp');
let parsed = parseFlp(buffer);

// Remap paths (e.g., disk migration)
parsed = rewriteSamplePaths(parsed, (oldPath) => {
  return oldPath.replace('D:\\Samples\\', 'E:\\NewSamples\\');
});

writeFileSync('my-project-migrated.flp', serializeFlp(parsed));

Modifying time information

import { readFileSync, writeFileSync } from 'fs';
import { parseFlp, serializeFlp, readProjectTimeInfo, writeProjectTimeInfo } from 'ts-flp';

const buffer = readFileSync('my-project.flp');
let parsed = parseFlp(buffer);

// Read time info
const timeInfo = readProjectTimeInfo(parsed);
console.log(`Created on: ${timeInfo.creationDate}`);
console.log(`Work time: ${timeInfo.workTimeSeconds} seconds`);

// Modify creation date
parsed = writeProjectTimeInfo(parsed, {
  creationDate: new Date('2024-01-01'),
  workTimeSeconds: 3600, // 1 hour
});

writeFileSync('my-project-modified.flp', serializeFlp(parsed));

API

Main types

interface ProjectMeta {
  name: string | null;
  description: string | null;
  artist: string | null;
  genre: string | null;
  bpm: number | null;
}

interface ProjectTimeInfo {
  creationDate: Date | null;
  workTimeSeconds: number | null;
}

interface SampleRef {
  eventIndex: number;
  path: string;
}

interface PluginRef {
  name: string | null;
  vendor: string | null;
}

Functions

Function	Description
parseFlp(buffer)	Parse a .flp buffer into a ParsedFlp structure
serializeFlp(parsed)	Serialize a ParsedFlp structure to buffer
readProjectMeta(parsed)	Read project metadata
writeProjectMeta(parsed, meta)	Modify project metadata
readProjectTimeInfo(parsed)	Read time information
writeProjectTimeInfo(parsed, info)	Modify time information
listSamples(parsed)	List all samples in the project
rewriteSamplePaths(parsed, mapper)	Batch rewrite sample paths
listPlugins(parsed)	List all plugins (VST and native)
getFlVersion(parsed)	Get the FL Studio version string
getPPQ(parsed)	Get the PPQ (Pulses Per Quarter note)

Constraints and limitations

What this library does

• Non-destructive read and write of .flp files
• Byte-for-byte preservation of unmodified data
• Compatibility with FL Studio 11.5+ (UTF-16LE strings)

What this library does NOT do

• Full editor for patterns, mixer, playlist, automation
• Create .flp files from scratch
• Guarantee VST vendor availability (returns null if not serialized)
• Support compressed (zipped) .flp files

Architecture

src/
  generated/
    events.generated.ts    # Event constants
  io/
    BinaryReader.ts        # Binary reading
    BinaryWriter.ts        # Binary writing
  parser/
    FlpParser.ts           # .flp Parser/Serializer
  api/
    ProjectApi.ts          # High-level API
  index.ts                 # Entry point

Development

# Install dependencies
pnpm install

# Type checking
pnpm run typecheck

# Tests
pnpm run test

# Build
pnpm run build

Credits

• PyFLP - Reference implementation for FL Studio file format
• smart-buffer - Binary read/write
• protobufjs - VarInt encoding

License

GPL-3.0

---

Acknowledgements

A huge thank you to @demberto (PyFLP), @monadgroup (FLParser), and FLPEdit for their incredible reverse-engineering work on the FL Studio .flp format.

This project would never have been possible without them.