How to get peak audio quality and lowest video quality? What are the best options to use to get optimal audio clarity for transcription, and minimal video to be used by the transcription service?  

Our videos are all meetings, and we're sending them to a service for transcription services - video quality is of no concern, but audio quality of the speakers is.  

Everything I've found is a complicated discussion about channels/tracks/mapping, etc., and frankly everything is about achieving peak video at the same time, so I'm confused about which options work on which tracks, and at this point don't even know what I should be googling.

Clarification
The source video can vary, depending on the circumstances of the meeting recorded.  It can be an enormous mpeg  or a smaller mp4 compressed "somehow".  The ffmpeg output VIDEO will be very small, 320:240 or similar, but I need as much of the original AUDIO (improved if possible) as I can get into the output mp4 file for the transcription service to have the best we can provide them.
It's not entirely clear what you mean by improved audio, but here are three ffmpeg-based options that should get you what you need. Just combine the appropriate code below. I've included an audio conversion to high bitrate aac in all of the commands, but this will not actively improve your audio. If you're looking to optimize the audio for voice, check out ffmpeg's highpass, lowpass, and anequalizer audio filters to filter out unwanted high end and low end frequencies, and to enhance vocal frequencies (probably around 1khz and 5kz).

This line processes all of one file type in a folder. Just cd into the appropriate directory. Replace [original file extension] with your file extension, eg. for i in *.mov; do

mkdir output; for i in *.[original file extension]; do


Use that first line, plus one of the following

Option 1) -vn will ditch the video altogether. Consider just sending audio files.

ffmpeg -i [input] -vn -acodec aac -b:a 320k [output];done


Option 2) -vf scale will scale all your videos into a smaller size without messing with the audio.

ffmpeg -i [input] -vf scale=320:240 -crf 30 -acodec aac -b:a 320k [output];done


Option 3) The first line gets the duration of your video $t using ffmpeg. The second line creates black video to replace your video with, then uses -map to combine the new black video and the audio. Then it uses -ss and -t to set a start and end time $t. Replace [original file extension] with your file extension, eg. "$(basename $i .mov).mp4"

You should really only consider using this if your transcription service demands a video file, but either of the previous options is probably a better choice.

t=$(ffmpeg -i "$i" 2&gt;&amp;1 | grep "Duration"|grep -o '00:*.*'|cut -f1 -d","|awk -F: '{seconds=($1*60)*60; seconds=seconds+($2*60); seconds=seconds+$3; print seconds}');

ffmpeg -f lavfi -i color=c=black:s=2x2:r=1/1 -i "$i" -map 0:v -map 1:a -acodec aac -b:a 320k -ss 0 -t $t "output/$(basename $i .[original file extension]).mp4";done



Again, if your transcription service doesn't care about or even want video, you could shortcut all of this and just send them high quality wav files.
ffmpeg -i [input.mp4] [output.wav]