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Comment by bluelightning2k | Hacker News Reader

As a developer it's rare to see something which leaves me feeling "how would you even build something like that..." but this is one of those. Huge cudos for even attempting and following through with something like this!

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I notice it's written in Ember, which is billed as the framework for ambitious web developers -- in this case, it definitely checks out.

YAAAAAS ember is so good

you follow HN, and some guy posts a video editing js library, another guy builds an app taking that library further, you get inspired and build something even bigger.

You start by building your knowledge around computer graphics and modern web development, basically WebGL and modern web APIs have made doing sophisticated graphic applications on the browser. Only limitation right now I see is single threaded limitation on the browser.

What about workers? Isn’t it basically the same as offloading computation heavy work to separate thread? Also, we have WebAssembly. Afaik, js threads can now share memory using SharedArrayBuffers. So I don’t think we have this single thread limitation anymore :)

Idk about this specific app, but the main problem with workers is that any data their working on needs to be copied in or side-loaded into them once they spin up. I imagine for huge video files, having each worker load up a separate copy could be a bottleneck.

> the main problem with workers is that any data their working on needs to be copied in or side-loaded into them once they spin up

Isn't this no longer an issue thanks to SharedArrayBuffer?

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

I believe the ONNX Runtime uses this for multithreading on the web, see https://github.com/nagadomi/nunif/issues/34

Ooh. Interesting. I wrote my last worker-based app a couple years ago for chunking and crunching some large datasets. I'll have to give this a go one weekend.

Indeed, Pikimov is using SharedArrayBuffers to decode video frames outside of the main thread

yeah i'm gonna need a TLDR of the major moving parts. how do you even do video editing in the browser? is there a "ffmpeg in the browser"? is that the basic building block?

We've been working on the Web Codecs API for a few years now. It only handles encoding and decoding media codecs, ffmpeg does much more (container handling, filters and everything needed really).

Web Codecs can take a compressed media packet and get you the decoded image or audio buffer it corresponds to. Conversely it can take audio or images with timestamps and get you a series of encoded media packets you can then containerize (we say mux) and get you e.g. an mp4 file.

https://w3c.github.io/webcodecs/

Can I just say that I was disappointed by the Web Codecs API leaving muxing the end result as a "draw the rest of the fucking owl" thing.

> is there a "ffmpeg in the browser"?

I don't know if this project uses it, but there's ffmpeg.wasm [1].

1: https://github.com/ffmpegwasm/ffmpeg.wasm

Actually it is: https://github.com/ffmpegwasm/ffmpeg.wasm, but for this particular project it seems using mp4box from gpac

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