ffipeg 0.1.1+4

Generate Dart FFI bindings to FFmpeg with a simple library annotation.

ffipeg

Easily generate Dart FFI bindings to FFmpeg for use in your project in 3 steps:

1. Add a library annotation;
2. Run build_runner;
3. Import the generated file, ffi, and go!

Example

(Incomplete; for illustrative purposes only; see ffipeg_muxer package for full working example.)

ffmpeg.dart

@FFmpegGen(
  versionSpec: '>=7.1 <8.0',
  excludeAllByDefault: true,
  functions: FFInclude({
    'av_compare_ts',
    'av_interleaved_write_frame',
    'av_log_set_level',
    'av_packet_alloc',
    // ...
    'avio_open',
  }),
  structs: FFInclude({'AVFormatContext', 'AVIOContext', 'AVPacket'}),
  enums: FFInclude({'AVMediaType'}),
  macros: FFInclude({'AVIO_FLAG_WRITE', 'AV_NOPTS_VALUE', 'AV_LOG_.*'}),
)
library;

import 'dart:ffi';
import 'dart:io';
import 'package:ffi/ffi.dart';
import 'package:ffipeg/ffipeg.dart'; // Exports `@FFmpegGen` Annotation
import 'ffmpeg.ffipeg.dart'; // Generated _name_.ffipeg.dart file with FFI bindings

void main() {
    final dylib = DynamicLibrary.open('/path/to/ffmpeg')
    final ffmpeg = FFmpeg(dylib);
    ffmpeg.av_log_set_level(AV_LOG_DEBUG);
    final videoInputCtx = calloc<Pointer<AVFormatContext>>();
    final videoPkt = ffmpeg.av_packet_alloc();
    final videoPktPtr = calloc<Pointer<AVPacket>>();
    final videoFile = "/path/to/video/file.mp4";
    if (0 != ffmpeg.avformat_open_input(
        videoInputCtx, videoFile.toNativeUtf8().cast(), nullptr, nullptr)) {
        throw Exception('Failed to open video file: $videoFile');
    }
    // ... do more stuff ...
    // We're dealing with C ... be sure to clean up resources!
    ffmpeg
        ..avformat_close_input(videoInputCtx)
        ..av_packet_free(videoPktPtr);
    if (videoPktPtr != nullptr) {
        calloc.free(videoPktPtr);
    }
    if (videoInputCtx != nullptr) {
        calloc.free(videoInputCtx);
    }
}

Features

• This package is basically a wrapper around FfiGen() that uses build_runner and makes it more accessible as part of a standard build process. It offers reasonable defaults for FFmpeg.
• Specify your own headerPaths to FFmpeg header files, or use default included headers. If supplied, headerPaths will be tried in order, so multiple build platforms can be supported.
• Specify which FFmpeg libraries (FFmpegLibrary.avCodec, etc.), (all by default), should be included.
• Pass standard FfiGen() include/exclude options via strongly-typed options of Set<String> for functions, structs, macros, enums, etc. using FFInclude({...}), FFExclude({...}), ffAllowAll, or ffDenyAll.
• Customize the generated class name for functions (FFmpeg by default).
• Pass custom llvmPaths to FfiGen() (optional).

Getting started

Prerequisites

• Flutter is not required. Only Dart + the package dependencies are required for code generation.
• Actually running your FFI code requires an FFmpeg binary (either executable CLI or dylib, e.g. in the fvp package for Flutter).
• This package does not require fvp or its mdk-sdk. Any FFmpeg binary built with the functions/features used and compatible with both the target system and the version of headers used to build the bindings will work.

Installation

• Add the 4 required packages:

dart pub add ffipeg
dart pub add ffi
dart pub add --dev ffipeg_builder
dart pub add --dev build_runner

Usage

• You will need to ensure the FFmpeg binary is available in your built Flutter app or Dart executable's path.
  • You may need a specific Platform switch to specify the path/name passed into the DynamicLibrary() constructor.

Refer to the FFmpegGen class source documentation for specific usage of the annotation.

Refer to the example code above to get started, or ffipeg_muxer package for a working CLI/Dart class example demonstratng how to mux an audio and video file without transcoding (copies the codecs).

Premise

There is currently no simple way of including the FFmpeg binary in a cross-platform Flutter desktop app. ffmpeg_kit_flutter does not offer a Windows or Linux version (Why not? They already have a build pipeline for 3 platforms...).

The only solution I found was fvp, which includes the FFmpeg binary via its bundled mdk-sdk, but it offers no FFmpeg API itself. And including both fvp and a built FFmpeg binary in my app would introduce too much bloat for the one function I needed.

Therefore, I learned to use FFmpeg through FFI and created this package.

Contributing

Contributions are welcome, especially if any bugs are found. Please open an issue in the repo at https://github.com/dra11y/ffipeg-dart.