Enable pausing and resuming of stream

[yannikwirbs]

Video and audio output pipe are on hold while paused.
There is no video or audio in discord.
Maybe there is a way to implement a way to send a still image to the video.
Video and audio are not desyncing.

REFERENCE ISSUE: #5

[longnguyen2004]

I'm wondering how this will behave in an actual live stream, and whether stream backpressure will be a problem.
Also, eloquent-ffmpeg has a built-in pause and resume function, maybe we should look at that as well?

Repeating the last frame is definitely not possible, since it'll break the bitstream.

[longnguyen2004]

Investigating RFC 7728 is also interesting Ignore, this is for a receiver to request a pause

[dank074]

This will also only work if noSleep is disabled.

From looking at eloquent-ffmpeg it seems it just suspends the process and then resumes it, like some people were already doing using SIGSTOP and SIGCONT

[longnguyen2004]

like some people were already doing using SIGSTOP and SIGCONT

And it also works on Windows using the undocumented NtSuspendProcess and NtResumeProcess functionns, so that's a plus.

I also wonder how the functionality should be exposed to user code. Maybe we'd need to create some kind of playback controller object, with play(), pause() and stop() functions.

[BitcircuitEU]

@longnguyen2004 while implementing ffmpeg api in nodejs maybe make a pause function that stores current timecode of demuxing and continue from there if possible. Not sure if SIGSTOP and SIGCONT is that reliable.