Convert MOV to MP3

Most phone video is not about the pictures

An enormous proportion of the video on people's phones was recorded for its sound. Interviews, lectures, rehearsals, a child saying something, a mechanic explaining a noise. The camera was running because that is what the phone does, not because anyone intended to watch it back.

That is why this conversion is so common and so satisfying. A five-minute MOV might be eighty megabytes; the audio inside it is perhaps four. The file becomes something you can email, transcribe, put in a podcast editor, or keep without thinking about storage.

How it works

The video track is discarded — not decoded and thrown away, simply not carried into the output — and the audio is re-encoded to MP3 at a high variable-bitrate setting. iPhones and Macs record AAC, so this is a lossy source becoming a lossy target, which costs a small amount of quality that speech does not reveal.

Because nothing touches the frames, the conversion takes about as long as reading the file. This is the cheapest thing you can ask a converter to do.

When the M4A route is better

If whatever receives the audio can read .m4a, extracting the AAC track without re-encoding is strictly better: it is instant, and it is bit-for-bit the audio the phone recorded. Podcast software, most modern editors and every Apple device handle M4A without complaint.

MP3 is the right answer when the destination is unknown or old — a car stereo, a transcription service with a fixed list of formats, a colleague's laptop. The small quality cost buys a file nothing refuses, and for spoken audio there is nothing audible to trade away.

What conversion cannot do

It cannot move the microphone. The single biggest determinant of how usable a phone recording is turns out to be how far the phone was from the person speaking, and that was decided when you pressed record. Extracting the audio makes the recording portable and does not make it clearer.

Why the file shrinks so dramatically

People are often suspicious of the size difference, as though something beyond the picture must have been lost. It has not. A minute of 1080p video is roughly twenty megabytes of images and roughly one megabyte of sound, because images are enormous compared to audio and always have been.

Removing the video is not compression, it is omission — the same reason a transcript of a film is a few kilobytes. The audio you get is as complete as it was inside the MOV, minus the small cost of encoding it once more.