chore: Allow to change cwd of transcoder ffmpeg

[elthariel]

As mentioned earlier, I want to support 2 pass VP9 encoding in my app, and the process produces a logfile in the current working directory.

Could have either somehow managed to pass an absolute path to the encoder, but it would have been a bit complicated or would have broken the re-usability of presets

Or I could just chdir the spawned process.

I went for the latter. This add a bit more code that I'd have liked, but when I added the spawn opt to FFMPEG::IO methods, I thought it would be better to add the option everywhere for homogeneity of the interface.

WDYT ?

[bajankristof]

Hi again @elthariel! Thanks for opening the PR, I'll try to take a look at it next week!

[bajankristof]

Okay, so taking a better look I don't think this needs to be handled on the gem level. The way you should do it is by wrapping the transcoding calls in a Dir.chdir block. That way the FFmpeg process will execute in your desired location without needing to change the gem or expose anything else other than what's strictly needed.

Do you think this solves your problem? Or is there something very specific that I don't yet see about your workflow?

[bajankristof]

I'm going to close this PR for now, feel free to reopen it if the answer did not suffice.