sanjayradia said:
Q1 The first command "FFmpeg -i original.mp4 original.mp3" simply figures out that it copying the audio and not data merely by the fact that the output file name ends with mp3? I tried it it works and it converted from 96kbs to 64bits mp3 using lame. Is this conversion of kbp automatically based on matching quality or a default? Normally you want to simply use similar level of compression or not convert and simply copy - not possible in this example as ac and mp3 are different i guess? Any tips on options on extracting as close to original or keeping it same.

Q2) in the second example, again my mp3 file got converted to a different kbs - how would one ask that simply copied as is. add a -c:a copy? Does .mp4 allow the audio to be mp3 format or does it require ac?

Welcome to Ten Forums.

The first command determined that audio is the required output from the .mp3 extension of the output file. I believe the conversion was a default. If you don't want the defaults you can specify the audio sample rate and the bit rate for the conversion, eg:

FFmpeg -i original.mp4 -ar 48000 -b:a 192k original.mp3

There is (very) comprehensive documentation on the ffmpeg site: ffmpeg Documentation

But if you'd prefer not to wade through all that, if you Google for "ffmpeg" followed by a few words describing what you want to achieve then (as ffmpeg is so widely used) you'll almost certainly find someone has asked (and been answered) before. That was how I learned to use it