FFprobe input to extract defaults.

[matvp91]

We've got an Input and a Stream type. An ffmpeg job is scheduled with a full input and stream.

What we can do is run an ffprobe child job first, and once that's finished we can schedule each ffmpeg job separately.

This way we use the ffprobe result to fill in defaults directly from the input source, without forcing the user to know everything upfront. I can imagine people don't know the channel count for every individual asset that's about to be transcoded.

{
  type: "audio";
  path: string;
  // We can make this optional and use ffprobe to potentially extract the language
  language?: LangCode; 
}

There's a few mandatory values (such as a text track MUST specify a language, or we won't be able to match it) but we can let the API handle sanity checks and stop early when a value is not provided for a required field.

Top of my head but we can probably probe for the following fields:

• language (for audio, default to "unk")
• framerate (for video, I don't think this can be optional)
• resolution (for video, we can remove the "skippable job" logic and not schedule an ffmpeg job at all if we're upscaling)
• channels (for audio, default to 2)