MP4 to MP3: Getting the Audio Out of a Video

Yes, you can convert MP4 to MP3: an MP4 is a container that holds a video track and an audio track, and converting pulls the audio track out and saves it as an MP3 file. The picture is dropped. The sound cannot come out better than it went in, so a 128 kbps source stays a 128 kbps source whatever bitrate you pick for the MP3.

What actually happens to the file

An MP4 file is a box with separate streams inside. Usually there is one video stream and one audio stream, and the audio is most often AAC. When you ask for an MP3, the converter does two things. It discards the video stream, and it decodes the audio and encodes it again as MP3.

That second step matters. AAC to MP3 is a lossy format to lossy format change. Both formats throw away detail the ear is least likely to miss, and a second pass throws away a little more. For speech, lectures and most music played on phone speakers or earbuds you will not hear it. On a good pair of headphones with a quiet, detailed recording, you might.

Two things follow from this:

• The MP3 is never better than the audio in the video. If the clip was recorded with a poor microphone, or the video was already compressed hard for sharing, the MP3 carries all of that.
• A higher bitrate does not restore anything. It only gives the new encoder more room, so it adds less extra damage on top of what is already there.

If you want to see the AAC side of this in detail, our AAC to MP3 converter handles audio-only files, and the same re-encoding rule applies to it.

Which bitrate to pick: 128, 192 or 320 kbps

Bitrate is how much data the MP3 uses for each second of sound. More data means a larger file and, up to a point, a more faithful copy of the source. These are the three settings people choose between:

Bitrate	Size per minute (stereo)	Good for
128 kbps	about 1 MB	Speech, podcasts, lectures, interviews, voice memos
192 kbps	about 1.4 MB	General music listening, a sensible default
320 kbps	about 2.4 MB	Music from a clean source, when file size does not matter

Those sizes are straight arithmetic: kilobits per second times 60, divided by 8. A one hour lecture at 128 kbps is roughly 58 MB, while the same hour at 320 kbps is about 144 MB.

A few rules of thumb that hold up:

• Match the source, do not exceed it. If the video's audio track is 128 kbps AAC, encoding at 320 kbps MP3 makes a file more than twice as big with no extra detail. Check the source first if you can. Most video players show the audio bitrate in the file properties or media information panel.
• Speech needs less than music. Voices sit in a narrow band of frequencies, so 128 kbps is plenty, and many people pick even lower for spoken word to save space.
• 192 kbps is the practical middle. It is the setting to use when you do not know the source and do not want to think about it.
• 320 kbps is for people who plan to listen on good equipment and have a good source. For a screen recording or a phone video from a noisy room, it just stores noise more carefully.

Constant and variable bitrate are the other choice you may see. Constant bitrate uses the same amount of data every second. Variable bitrate spends more on complex passages and less on quiet ones, so it often gives a smaller file at similar quality. Constant is the safest for old players and car stereos, and variable is fine for almost everything else.

MP3, M4A or WAV: which target format

MP3 is not the only place the audio can go. The right choice depends on what you will do next.

MP3 plays on everything: phones, cars, old players, smart speakers, upload forms. If the file is going to someone else or into a device you do not control, this is the safe pick. The cost is the second lossy pass described above.

M4A (AAC) is often a better fit when the source audio is already AAC, which is common in MP4 files. At a given bitrate AAC generally sounds as good as or better than MP3, and a few tools can copy the existing AAC stream into an M4A file without re-encoding at all, which avoids any extra loss. Support is wide on phones and computers but not universal on older hardware. Our MP3 vs AAC comparison goes through the trade-offs.

WAV is uncompressed. It stores the decoded sound exactly, at roughly 10 MB per minute for CD-style stereo. It will not make a lossy source sound better, because the detail removed when the video was made is gone for good. What WAV does give you is a file that can be edited and re-saved without another round of quality loss. Pick it if the audio is headed into an editor, a sample, or a mastering session, and convert to a smaller format at the end. See MP3 vs WAV for the longer version.

A simple way to decide:

1. Sharing, uploading or playing on unknown devices: MP3 at 192 kbps.
2. Source audio is AAC and you only want it on modern phones and computers: M4A.
3. Going into an editor first: WAV, then export to MP3 or M4A once at the end.

Doing it on a computer or online

You have two routes, and neither is wrong.

On your own computer. Desktop media players and editors can usually do this. VLC, for example, has a Convert / Save option under the Media menu where you choose an audio profile such as MP3. Video editors and audio editors can export audio only as well. The upside is that the file never leaves your machine and there is no size limit beyond your disk. The downside is setup: you need the software installed, and finding the right profile and bitrate settings takes some clicking the first time. The exact menu names change between versions, so treat the steps as a pointer rather than a recipe.

Online. Upload the video, pick MP3, download the result. This is quicker for a one-off, works on a phone, and needs nothing installed. The trade-off is that the video is uploaded to a server, so think twice before using it for something private. On 1converter, MP4 to MP3 takes the audio out for you. Download links last 24 hours on the Free plan and without an account, and 7 days on paid plans, after which the files are deleted. The Free plan accepts files up to 50 MB, and a video converted to MP3 counts as one operation against your daily allowance.

If you only want a section of the sound, say one song from a long recording, trim the video first or use the audio bitrate tool afterwards to shrink a file that came out larger than you need.

Private Mode, which converts in the browser without an upload, covers images and PDFs only. Video and audio always go to the server.

Before you convert: a note on rights

Pulling the sound out of a video you own, recorded yourself, or have permission to use is fine. Audio ripped from someone else's video may be protected by copyright, so check the terms before you reuse or share it.

Quick checklist

• Check what the source audio is. Do not choose a bitrate far above it.
• Speech: 128 kbps. Unknown source or general music: 192 kbps. Clean source and good headphones: 320 kbps.
• Going into an editor: choose WAV first, compress at the end.
• Keep the original video until you have listened to the result all the way through.
• Remember the loss is one-way. You cannot turn an MP3 back into the original sound.