suryatmodulus/libav.wasm

libav WebAssembly port

libav.wasm

libav WebAssembly port.

• Background
• Get Started
• Try it!
• Configuration

Background

libav (incl. libavcodec, libavformat, …) is the library behind FFmpeg to record, convert and stream audio and video. This repository aims to port libav to WebAssembly to allow users edit video and audio directly inside the browser.

Why not ffmpeg.wasm?

ffmpeg.wasm ports FFmpeg to WebAssembly using a more coarse-grained approach (you can imagine ffmpeg.wasm as an extremely large function, once it starts to run, there isn't much you can control.), it works but also suffers from the isolation of C and JavaScript world which makes it hard to develop and improve.

The ultimate goal of libav.wasm is to enable a ffmpeg.wasm with better developer experience (DX) and potentially be the foundation to fix issues like performance and more.

Get Started

We use docker to achieve a (hopefully) cached and reproducible build, so it is required to install docker 19.03 or above before you run any build script.

• Build libav.wasm

# default build
$ bash build.sh

# build with details
$ bash build.sh --progress plain

If nothing went wrong, you should find libav assets in dist/.

Try it

A few examples can be found in example/, feel free to try and see how it works in action.

As these examples use video files in testdata/, you need to do a git submodule update --init first

• metadata: use libav.wasm to extra video metadata

make run-metadata

• transcode: use libav.wasm to transcode mp4 to a gop fixed mp4

make run-transcode

Configuration

libav.wasm is built using tools/libraries with version:

Name	Version
emsdk	3.1.18
FFmpeg	n5.1
x264	0.160.x