Only force JACK output if user did not specify --no-audioengine

[jose1711]

IIUC blitzloop uses Jack only for adding Karaoke effect. If such effect is not needed (e. g. b/c echo effect is integrated into an USB mixer/soundcard) - i. e. a user specifies --no-audioengine as command-line switch then I believe it would be better not to force it (and let mpv use the default driver).

[marcan]

This is just an option to blitzloop, --mpv-audio-device which defaults to jack. You can specify any other mpv ao with that. I believe you can just say --mpv-audio-device= (leave it blank) to make mpv use the default driver.

[jose1711]

I understand the option, but I think the logic should be slightly changed:

1. blitzloop requires jack only for microphone (echo) effect
   this is the default use-case when no options are passed and there's nothing wrong with that

2. user decides not to use microphone effect (maybe (s)he does not need/want it or it's implemented in a different way)
   user passes --no-audioengine as hinted by application help. As current audio system may be pulseaudio (or any other - supported by mpv) I don't think forcing jack or requiring user to also specify --mpv-audio-device for a non-jack results in a proper user experience (simply because adding jack adds complexity while bringing no benefit in this particular example).

To put in into simple words: I believe specifying --no-audioengine should imply --mpv-audio-device= (i. e. default ao driver).

[marcan]

Ok, so just a "dynamic default" if you will. AFAIK the sane way of doing that is just defaulting to None and replacing that with the appropriate default in the mpvplayer code.