Answered on Quora by Mark Urso, Owner at River Song Music
This is very ambitious! To “mix movie audio” is as deep a subject as mixing any audio. So the question includes a request for instructions on how to become an audio engineer and run a sound studio.
The answer is, the same way you would mix audio if it were not in a movie. Detach it first, bring it into your audio workstation, and fix it. I’d recommend doing your video editing first, if possible. If you can, then you know you won’t be slicing the video (and audio) and have to realign them later. If you end up with a complete, edited and trimmed video, with a single audio track that corresponds to it, take that single audio track out, bring it into your audio program, process it without changing its length (at all), and when you replace it, it should still be lined up. If not, look for visual clues and line it up manually if you have to, once you’re back in your video editing console.
If you’ve sliced and diced your video, before pulling the audio out, which is likely, and you are looking at sliced video with sliced audio underneath it, you might be able to delete all those AUDIO slices, leaving the video slices AS IS, except leave one of the audio pieces, just the very last one (usually) (it has to be one that is correctly synched), and pull its handle to cover the whole video. That would be applicable, for example, making a music video, where the song underneath is one single product, and you don’t need multiple audio lines under the video in the video editor.
If you’re on a Mac, Quicktime 7 (you have to buy it) will allow you to extract the audio cleanly from any video file. I’d recommend replacing it directly into the video software project after adding your effects.
Note, everything changes if you change the length of the audio or cut it up in the DAW. Depending on project and workflow, some of the things I’ve suggested might be applicable, and help you get going!
Your question includes two entire universes of possible information. It’s very broad. But if you are looking for good plugins, you might break that out into separate questions for different purposes to get some Quora love on that. There’s a free compressor called “Rough Rider” which, when you use it gently, can be a generally-useful tool if your tool bag is empty, along with all the many plugins that come with your computer.
Using your field recorder, get the levels up high without overloading. Bring headphones to the gig and plug them into the field recording to listen to the pass-through. When you get the audio and footage back home, you will benefit from basic massaging of the audio, which should include (in the DAW), normalizing (these days people produce loud, up to about -2dB max, so you want your video to sound correct volume-wise in today’s environment) (radio typically expects -6dB).
Once normalized, bring up a compressor, lightly, and listen loudly.
Some other basic tools, and they are all used based on what you hear in conjunction with each other, include a frequency equalizer and reverb. All must be used sparingly. Beyond that, music mixing is an art, and far more complicated than can be treated here.
Original question: What is the best way to go about mixing movie audio, and what are the best plugins available to achieve the best sound after using a field mixer to record the audio?