[Encoder] Memory issues in iOS, failing encoding

[zeh]

The encoding is generally failing in some situations where memory is constrained:

• iOS: fails with a "malloc of size 34241728 failed" error (not currently reported to the progress bar; tracked as Encoder must properly parse error messages in case of failure #13)
• Firefox on Android: fails fatally, completely removing the page (no diagnosis yet)

Specifically for iOS, @[email protected] produced some good reports on the issue; see thread: https://snoot.tube/@viv/110857551521005861

We might need a custom version of the wasm FFmpeg dependency with memory settings tweaks during compilation.

Requirements

• Encoding works in Safari iOS
• Encoding works in Firefox Android

[zeh]

Updating to @ffmpeg/ffmpeg v0.12.4 with 3dd690a seemed to have done something - it's working in Firefox Android with no crashes.