Samples restrictive

The video/audio samples provided in samples/ all have issues that make them difficult to use to demonstrate WebCodecs in isolation (which, for me, makes it difficult to use them with a polyfill or, thus, to demonstrate or test said polyfill):

• MP4 Decoding uses a codec controlled by the Misanthropic Patent Extortion Gang, so it's unlikely to be supported by any fully F/OSS implementations.
• Webcam in Worker uses the MediaStreamTrackProcessor API, which is a separate API entirely (and also experimental, and somewhere between difficult and impossible to polyfill).
• Capture to File uses MediaStreamTrackProcessor and the FileSystem API, which is also a separate, experimental API.

Admittedly, this is of particular nuisance only to me, because it means I can't say "supports the WebCodecs samples", but regardless it's a breadth issue.

It'd be nice to see simple transcoding (VP9/FLAC to VP8/Opus, for instance), or even just a trivial decoder or encoder with no surrounding bells and whistles. I have some in-progress samples (using my polyfill) at https://github.com/ennuicastr/libavjs-webcodecs-polyfill/tree/master/samples/ .

Start by reviewing the existing samples/ directory to identify which APIs and codecs each example depends on, then compare the requested scope with the linked polyfill samples. Done means adding a simple WebCodecs-focused example that avoids the unrelated experimental APIs and restrictive codec dependency described in the issue.