MOV is the QuickTime container Apple designed, and the one a Mac or an iPhone writes before anything else gets to touch it. AAC is Advanced Audio Coding on its own, lossy, and the encoding that replaced MP3 nearly everywhere it mattered. ffmpeg sits between the two, and this page says exactly what happens to a MOV file on the way to becoming an AAC one.
What runs when a MOV file becomes AAC
ffmpeg held to a single thread, on a machine we rent and watch. Your MOV file is uploaded once, ffmpeg runs once, the AAC comes back, and neither file is kept. MOV to AAC is one of the 3649 pairs that engine was probed on with a real file, which is why it has a page here and why the pairs the probe could not prove do not.
What survives from the MOV into the AAC
The sound, and nothing but the sound. ffmpeg passes -vn on every audio target, so the MOV video stream is dropped at the demultiplexer and never reaches an encoder at all. That is why this pair is quick: the picture is the expensive part of a MOV file, and this pass does not look at it.
The running time. The AAC plays for exactly as long as the MOV did, because nothing on this path trims, cuts or speeds anything up.
The sample rate and the channel layout of the MOV audio track, carried into the AAC unchanged wherever the encoder accepts them, and resampled only where it cannot.
What MOV to AAC costs you
The picture, all of it, and on purpose. The MOV video stream is dropped before any encoder sees it, and the AAC that comes back is sound alone. Nothing in the AAC remembers there was ever an image, and no later conversion can put one back.
Cover art carried inside the MOV. ffmpeg counts an attached picture as a video stream, so the same -vn that drops the film drops the artwork with it. Keeping it is worse: on several audio containers the mux then fails outright with an error nobody can read.
Any second audio track, and the subtitles. ffmpeg selects one stream out of the MOV, and an AAC file has nowhere to put a subtitle track in any case.
Exactness, one more time. The audio inside the MOV was compressed once already, and AAC compresses the decoded result again. Two lossy passes do not cancel each other out, they stack.
If a model is going to read the AAC
An AAC file is a waveform, and a language model reads text, so handing an assistant this AAC directly gets you nothing. The AAC becomes useful the moment somebody turns the sound into words, and that is a separate job with its own page here. MOV to AAC is the step before it: get the sound out of the MOV in a container the transcriber accepts, then hand the model a transcript instead of a file it cannot open.
Running MOV to AAC against the real engine with a real file, ffmpeg wrote 27,317 bytes of AAC in 0.2 seconds, machine otherwise idle. That is one MOV file on one day and not an average, which is why the number is given together with the file that produced it.
The MOV to AAC verdict was reached by ffprobe, meaning the container was actually demultiplexed, recognised under the right name, and carried at least one stream. Which check was used matters, because they do not all prove the same thing, and a status code of 200 proves nothing whatsoever about whether the AAC file has anything inside it.
The same MOV file, sent somewhere else
Other outputs the probe measured out of a MOV file, so the cost of choosing AAC can be read against something. Sizes do not compare across engines, because each family was probed with its own MOV witness file.
MOV to GIF: 164,004 bytes in 0.1 seconds, verified by a format signature.
MOV to MP3: 24,768 bytes in 0.1 seconds, verified by ffprobe.
MOV to MP4: 45,683 bytes in 0.3 seconds, verified by ffprobe.
MOV to WAV: 266,318 bytes in 0.1 seconds, verified by ffprobe.
MOV to FLAC: 156,937 bytes in 0.1 seconds, verified by ffprobe.
MOV to OGG: 9,158 bytes in 0.2 seconds, verified by ffprobe.
Other ways into AAC, and what they measured
Among the published routes into AAC, MOV is the number 12 largest output of the 16 measured. The witness files differ, so this ranks the probe run and not your document.
MPG to AAC: 27,223 bytes in 0.2 seconds.
OGG to AAC: 27,598 bytes in 0.1 seconds.
OPUS to AAC: 27,353 bytes in 0.2 seconds.
WAV to AAC: 27,219 bytes in 0.2 seconds.
WEBM to AAC: 27,353 bytes in 0.2 seconds.
What we will not pretend about MOV to AAC
A MOV file over 150 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
A MOV to AAC run that passes 240 seconds is killed, and the ffmpeg process is killed with it. A run left behind would sit on one of the machine's two cores until somebody noticed.
The MOV file behind the measurement on this page was 3 seconds of 320 by 240 test pattern at 25 frames a second, with a sine wave on the audio track, built by ffmpeg for the probe itself. That is why MOV to AAC came out at 0.2 seconds, and it is not what your file will do. The measurement proves the pair works and says almost nothing about how long yours will take.
MOV to AAC costs half a credit per conversion, whatever the length of the MOV. That is the same as an image or a document here, and it is a measurement rather than a gesture: an audio target on this engine is done in under two seconds, where a video target can take minutes.
A MOV longer than 60 minutes is refused before encoding. ffprobe measures the MOV first and answers with a refusal, rather than starting a job the 240 second guard would kill halfway to the AAC.
MOV to AAC waits at the audio door, which is 2 slots wide and gives up after 5 seconds rather than making you wait twenty times the length of the work. Until the 30th there was one door for everything, and a single video transcode starved every audio conversion for its whole duration: an AAC that needed less than a second was answered with a refusal after twenty.
Nothing here reads what is inside the MOV. No transcription, no scene detection, no summary: MOV to AAC is a container and codec operation, and the AAC says exactly what the MOV said, in a different wrapper. The sound is the whole payload.
One MOV file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
MOV to AAC: what people ask
What actually converts my MOV file to AAC?
ffmpeg does it, held to a single thread, on a machine we rent and watch. Not a browser trick and not somebody else service: the MOV file is uploaded once, ffmpeg runs once, the AAC comes back, and neither file is kept afterwards.
How long does MOV to AAC take?
The probe measured 0.2 seconds for 27,317 bytes of AAC, on a 3 second file. An audio target scales far better than a video one: three minutes of source through this engine takes under a second, because only the sound is encoded. Past 240 seconds any run is stopped, and an audio one does not get close.
What do I lose going from MOV to AAC?
The one to know about first: The picture, all of it, and on purpose. The MOV video stream is dropped before any encoder sees it, and the AAC that comes back is sound alone. Nothing in the AAC remembers there was ever an image, and no later conversion can put one back.
Does the AAC still have the video in it?
No, and that is the entire point of the pair. The MOV picture is dropped before any encoder touches it, so what you download is sound only. If you wanted to keep the picture you wanted a video target, and it is priced differently because it costs differently.
Is MOV to AAC free?
There is a free allowance every month, and one MOV to AAC conversion costs half a credit against it however long the MOV runs. An audio target is charged per conversion and not per minute, because the engine encodes three minutes of sound in well under a second.