Is there a way to abort running transcodes, e.g. on invalidation? And does this library support GIF encoding (ffmpeg.js doesn't, afaik)?

The ffmpeg process comes from https://github.com/ffmpegwasm/ffmpeg.wasm-core, and the ffmpeg.wasm library is a wrapper to it. The .run() method is a Promise that resolves only when it receives the FFMPEG_END message, and there is clearly no way to abort it. And for your second question, as https://github.com/ffmpegwasm/ffmpeg.wasm-core is a port of C++ ffmpeg to Javascript, there are no difference in which features are implemented. And by the way, https://github.com/ffmpegwasm/ffmpeg.wasm-core/search?q=gif returns no result :/

Re abort: Too bad. :/ It seems that the lib exposed the worker's terminate() method up until v0.7.0: https://github.com/ffmpegwasm/ffmpeg.wasm/blob/v0.7.0/src/createWorker.js There's a request to reintroduce to reintroduce the feature here: https://github.com/ffmpegwasm/ffmpeg.wasm/issues/68 Tbh, I'm not even sure if the old terminate would have reliably stopped the process. Re gif support: AFAIK the supported codecs depend on the flags with which ffmpeg was compiled, and can heavily increase the binary. Here's a notebook for ffmpeg.js: https://observablehq.com/d/d4d995d29550a971 If you scroll down to the select that reads "-help" and select "-codecs" from it, you can see the support matrix.

ffmpeg.wasm supports gif! { const f=FFmpeg.createFFmpeg({log:true});f.load().then(()=>f.run('-codecs')) } > [ffout] DEV..S gif CompuServe GIF (Graphics Interchange Format)

OK, thanks for sharing the results of your research! It seems promising to replace various of my notebooks: https://observablehq.com/@severo/frameat, https://observablehq.com/@severo/asynchronous-canvas-recorder, https://observablehq.com/@severo/load-process-and-export-video. The drawback is that SharedArrayBuffer is still not supported by Firefox.

I came to your notebook to check what was wrong with mine, and it turns out that ffmpeg.wasm won't work on observablehq anymore, https://developer.chrome.com/blog/enabling-shared-array-buffer/ did I read that right?

You're right, I haven't noticed that it is not working anymore. I added the link to the chrome.com article in the error message. Thanks Radamés!

SharedArrayBuffer should now be available in all major browsers. Wanna file a feature request to investigate cross origin isolation for notebooks?

hi Fabian, that would be an interesting feature is this how you solve this? however isn't it disable for a security reason? if you enable any arbitrary notebook to have access to SharedArrayBuffer, couldn't Observable be exploited by bad actors? let say I make a puppet notebook that behind the scene is trying to access unauthorized memory https://googleprojectzero.blogspot.com/2018/01/reading-privileged-memory-with-side.html

I don't have the answers to these questions, but the article you linked has received some updates since you posted it. Hence my suggestion to create a feature request in order to explore the feasibility and implications.

I'd be curious to learn more about it! Thanks for exploring

Fun fact: SharedArrayBuffer can still be accessed via ``` SharedArrayBuffer = new WebAssembly.Memory({initial: 0, maximum: 0, shared: true}).buffer.constructor ``` but it will fail with "Failed to execute 'postMessage' on 'Worker': SharedArrayBuffer transfer requires self.crossOriginIsolated".