It's still unclear from your explanation how it's actually used in practice. I run thousands of ffmpeg conversions every day, so it would be useful to know how/

It's still unclear from your explanation how it's actually used in practice. I run thousands of ffmpeg conversions every day, so it would be useful to know how/if this is likely to help me. Are you saying that it's run once during a conversion as part of the process? Or that it's a specific flag that you give, it then runs this function, and returns output on the console? (Either of those would be a one-time affair, so would likely result in close to zero speed improvement in the real world).