ffmpeg: Add optional stdout callback

[kkuehlz]

:recycle: Current situation

When using ffmpeg, there are situations where it's nice to simply stream the output the stdout, especially when post-processing is intended to be done within the same program that launched ffmpeg. Right now, if you set the output to -, there is no way for the caller to capture that output.

I am using the ring-client-api, which depends on this class for transcoding the livestream. If I can get this merged, adding a PR to that repo will be next in order. https://github.com/dgreif/ring/blob/4b4e5611bafddc8ca4ad5baba35335c05879b5cc/packages/ring-client-api/streaming/streaming-session.ts#L132-L139

:bulb: Proposed solution

Add an optional callback for the user to process stdout data.

:gear: Release Notes

Provide a summary of the changes or features from a user's point of view. If there are breaking changes, provide migration guides using code examples of the affected features.

New option stdoutCallback added to FfmpegOptions struct. If you accept this PR, can you do a release so I can update the dependency in ring-client-api?

[donavanbecker]

@keur once you have resolved @dgreif comments, I will merge this into a beta where we have also update dependencies and then we can get a new beta version out.

[kkuehlz]

@keur once you have resolved @dgreif comments, I will merge this into a beta where we have also update dependencies and then we can get a new beta version out.

@donavanbecker Done. Btw, since you changed the base branch, it included a Discord Webhooks from latest as part of this diff. So I re-created my branch off beta-2.2.5 and force pushed.

[donavanbecker]

@keur once you have resolved @dgreif comments, I will merge this into a beta where we have also update dependencies and then we can get a new beta version out.

@donavanbecker Done. Btw, since you changed the base branch, it included a Discord Webhooks from latest as part of this diff. So I re-created my branch off beta-2.2.5 and force pushed.

yep that was in the latest branch already

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• Overall coverage decreased (-0.5%) to 27.985%

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Totals
Change from base Build 7452346226:	-0.5%
Covered Lines:	68
Relevant Lines:	183

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💛 - Coveralls

[donavanbecker]

@keur 2.2.5 has been released

[kkuehlz]

@keur 2.2.5 has been released

Thank you so much!!