Why do stereo and mono mp3 exports have the same file size?

Forum|Forum|4 years ago
November 1, 2021
1 reply
3027 views

My podcast is in video format, that's why I edit it in Premiere Pro. But I also want to export the audio-only version in mp3 format. The easiest way for me to go about this is to do it right from Premiere Pro. I want to use mono sound because of the smaller file size. But for some reason, mono and stereo exports both have the exact same file size. Why is that?

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Correct answer Averdahl

But for some reason, mono and stereo exports both have the exact same file size. Why is that?

By @Florian Walther

The bitrate specified is per file and not per audio channel.

Averdahl

Correct answer

Community Expert

But for some reason, mono and stereo exports both have the exact same file size. Why is that?

By @Florian Walther

The bitrate specified is per file and not per audio channel.

F

Florian WaltherAuthor

Known Participant

I'm sorry but I don't know what to do with that information. How does this relate to the mono/audio file size?

Averdahl

Community Expert

Thanks for the explanation. But why am I reading everywhere online that stereo mp3s have twice the file size as mono? Do stereo mp3s need 2x the bitrate to have the same audible quality?

But why am I reading everywhere online that stereo mp3s have twice the file size as mono?

By @Florian Walther

I don´t know.

I did a test with Adobe Audition and it provided the same result as Premiere Pro regarding stereo/mono file size at a given bitrate. Ask them what software they use and try it. Many "facts" on the internet are just myths or just untrue with nothing backing up their statements. It´s the same for video in general, lots of myths about things that none of them can prove right, or wrong.

Do stereo mp3s need 2x the bitrate to have the same audible quality?

By @Florian Walther

In theory, yes.

If you export a stereo file using 128 Kbps, 64 Kbps/channel will be used while doing the same for a mono file all 128 Kbps will be used on one channel. I have not tested and listened if one hear any difference.

mp3 is an effective codec though so it´s not like a stereo file will sound 50% worse than a mono file at the same bitrate. Going from stereo to mono will loose the stereo integrity, so i would never export to mono if the source is stereo depending on the content (music or talking) and the mix.

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