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

Community Beginner ,
Nov 01, 2021 Nov 01, 2021

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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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Audio, Editing, Export, Formats

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correct answers 1 Correct answer

Adobe Community Professional , Nov 01, 2021 Nov 01, 2021
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.

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Adobe Community Professional ,
Nov 01, 2021 Nov 01, 2021

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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.

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Community Beginner ,
Nov 01, 2021 Nov 01, 2021

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

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Adobe Community Professional ,
Nov 01, 2021 Nov 01, 2021

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


By @Florian Walther

 

When you export a stereo files, two channels, and set the bitrate to 128 the file will be let´s say 50 MB. If you now export a mono file, one channel, and use the same bitrate, iow 128, the file will still be 50 MB.

 

The resulting file size is not tied to either mono or stereo. The resulting file size is tied to the bitrate used upon export. If you want a smaller file, lower the bitrate.

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Community Beginner ,
Nov 01, 2021 Nov 01, 2021

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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?

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Adobe Community Professional ,
Nov 01, 2021 Nov 01, 2021

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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.

 

 

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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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Community Beginner ,
Nov 01, 2021 Nov 01, 2021

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Thank you for your answer! That clarifies my questions so far!

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