reference-types VS mediacapture-record

> It could be an interesting use case for WASM if the problem of passing data into the WASM VM cheaply (perhaps by reference) can be solved.

WASM Reference Types should hopefully solve this. The WASM working group seems to have some good momentum - so I'm hopeful this (or a similar replacement spec) will land sooner rather than later.

https://github.com/WebAssembly/reference-types/blob/master/p...

AFAIK GC is irrelevant for "direct DOM access", you would rather want to hop into the following rabbit hole:

- reference types: https://github.com/WebAssembly/reference-types/blob/master/p...

- interface types (inactive): https://github.com/WebAssembly/interface-types/blob/main/pro...

- component model: https://github.com/WebAssembly/component-model

If this looks like a mess, that's because it is. Compared to that, the current solution to go through a Javascript shim doesn't look too bad IMHO.

[1]: https://github.com/WebAssembly/proposals

A glance of the overview and spec seems to indicate that WASM will provide some primitive data types, and any GC language can build their implementation on top of it. As I understand it, it's heavily based on Reference Types[3], which allows acting on host-provided types, and is already considered part of the spec [4]. It doesn't remove the need for the 5 different runtimes to have their own GC, but it lowers the bulk that the runtimes need to carry around, and offloads some of that onto the WASM runtime instead.

[3]: https://github.com/WebAssembly/reference-types/blob/master/p...

They've talked about interface types, and added reference types, which is a stepping stone toward the GC extension proposal, which would be a stepping stone toward manipulating the DOM from the WebAssembly side, but their official roadmap page is more short-term.

Nope, WASM reference types, it has nothing to do with .NET type system.

> And there's been talk of exposing the JS GC to wasm for a few years. Hopefully when that stuff lands, it'll get easier to marshal objects across the gap.

You don't need a Wasm GC to do this. If you only need js objects to pass on to, say, the host's function or check is null or not, then reference types that are opaque external references: https://github.com/WebAssembly/reference-types/blob/master/p...

You can even do many more things if you export `Reflect` to WebAssembly: https://github.com/AssemblyScript/assemblyscript/blob/main/t...

Reference Types are available almost everywhere already (In Safari will be available after 15.0): https://webassembly.org/roadmap

Re: GC -- yes, indeed, the whole business with safepoints arose from the need to support Wasm reference types as a backend for Wasmtime or Firefox. No safepoints are needed for Rust (or other C-like) code.

Reference Types,

Courtesy of this GitHub thread, my currently working, but very inconvenient strategy to capture the video is to use mediaCapture(0) on the canvas element with MediaStreamTrackProcessor to pipe frames into WebM muxer from a package called webm-muxer.

WebRTC's RTCRtpSender.replaceTrack() method achieves "seamless" replacement of a MediaStreamTrack. I proposed the same be added to MediaRecorder, see Add replaceTrack method to MediaRecorder., Add replaceStream to MediaRecorder.

I guess this could be used to remux the broken files that are spitted by the MediaRecorder API, which have missing metadata that prevents from seeking and thus far has been ignored / sweeped away in Chrome [1], Firefox [2], and even the standard itself [3], which ignored in its design the basic fact that encoding any file should include a "closing" stage (where metadata is written) before yielding it as a finished file.

[1]: https://bugs.chromium.org/p/chromium/issues/detail?id=642012

[2]: https://bugzilla.mozilla.org/show_bug.cgi?id=1283464

[3]: https://github.com/w3c/mediacapture-record/issues/119