How can I convert stereo mp3 to mono WITHOUT reencoding?

Paco M. · Member Joined: 28 Jul 2003

Hi,

I have several stereo mp3 files with voice recordings. I need to convert them into mono in order to reduce their size. Original quality is not very good so that I would prefer not to reencode them.

Does anyone knows how can I mix both channels (or extract one of them) without mp3 reeconding?

Thank you in advance for your suggestions.

Paco

mats.hogberg · Modded Morloc Joined: 17 Jul 2002 Location: Sweden (PAL)

Nope. No can do.

/Mats
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Paco M. · Member Joined: 28 Jul 2003

What a pity!

There are other operations, like audio normalization, that can be done without reencoding. I expected so for stereo to mono conversion but .....

guns1inger · So Very Tired Joined: 01 Apr 2004 Location: Miskatonic U

I haven't normalisation done without re-encoding. MP3Gain can lift the gain of a file without re-encoding, but I don't believe it actually normalises the file. It can match the gain across a folder of tracks to give them a common volume - which is a type of normalising, I guess, but not in the manner you mean.

Regardless, what you are talking about is a structural change to the audio, so no dice
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ebenton · Posted: Aug 29, 2006 10:39

Have you tried just using brute force, with a "y" adapter cable to connect both left and right to one cable, and then input into whatever mono recording device you want to use?

mats.hogberg · Modded Morloc Joined: 17 Jul 2002 Location: Sweden (PAL)

That wont make the MP3 files much smaller in size...
I think the only way is to reencode to mono MP3 - don't really think the quality will suffer that much.

/Mats
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ebenton · Posted: Aug 29, 2006 11:29

I did not gather from the original post that reduced size was a goal.

SingSing · Member Joined: 30 Apr 2001 Location: U.S.A.

Too much sun shine for you.

jagabo · Member Joined: 09 Dec 2005 Location: none

mats.hogberg · Modded Morloc Joined: 17 Jul 2002 Location: Sweden (PAL)

No need rubbing it in, guys!

I think ebenton got the point long ago... We're all guilty of not reading every word before replying once in a while...

/Mats
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moviebuff2 · Member Joined: 21 Feb 2002 Location: United States

Hi Paco M.:

If you still want to convert your stereo files to mono, without reducing the size, Audio Cleaning Lab (ACL) may be of your interest. Actually, ACL may even improve the quality of your files.

Cheers

Paco M. · Member Joined: 28 Jul 2003

Thanks moviebuff2. I will look into Audio Cleaning Lab (I do not know this application) although I am mainly interested in reducing the size of the files by converting them from stereo into mono ... without reeencoding.

Enygma · Member Joined: 07 Feb 2002 Location: Canada

Since they are only voice recordings, have you bothered to check to see if the left and right channels are identical? Often times "stereo" sound clips are really mono but copied to both channels.

I'm not sure what software you could use to remove one of the channels and change it into a mono mp3.

For simplicity sake I would suggest re-encoding anyway. You won't lose that much quality for voice recordings.

jman98 · Member Joined: 08 Oct 2004 Location: Freedonia

Noahtuck · Posted: Aug 30, 2006 09:56

Why even bother removing a channel ?
Open it and if it's a stereo file just save it as a mono file

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psx_pirate · Posted: Aug 30, 2006 12:00

Sony Soundforge (not cheap) can do it .... just use the channel converter to convert from stereo to mono

NOTE: converting from stereo to mono will not reduce the file size ..... so save your money .... only by re-encoding to a lower bitrate will you reduce the filesize

Noahtuck · Posted: Aug 30, 2006 12:21

Hmmm...
Funny... i just opened a true stereo music file that was 977mb, changed absolutely Nothing, just opened it in Sound Forge 8.0, and saved it as a mono file and it is now 488mb

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mats.hogberg · Modded Morloc Joined: 17 Jul 2002 Location: Sweden (PAL)

The problem wasn't how to convert a stereo MP3 to mono MP3 - it is doing it without reencoding.

/Mats
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Noahtuck · Posted: Aug 30, 2006 12:32

Yep, i knew that

I'm still wondering why you would not just do it and see how it sounded

Also i tested it with a wav and it did lower the file size but not with an MP3,
Even if one side of the MP3 is muted then saved as a mono MP3 it does not reduce the size.
Man i hate MP3's

Oh well

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Originally a member since july of 2001
so i'm not a noob!!!!!!!!!!!
LONG LIVE TARANS!!!!!!!!
& if that don't tell you anything.....
Who's really the noob ??

psx_pirate · Posted: Aug 30, 2006 12:38

Using the channel converter in Sony Soundforge does not re-encode the mp3 .... and like i said previously it won't reduce the file size either .... converting mp3's from stereo to mono will make no difference to the file size

Cornucopia · Posted: Aug 30, 2006 15:31

The only apps that have been known to manipulate an mp3 stream WITHOUT re-encoding it have been: A-cut/join editors, B-ID3 tag editors, C-playback gain editors

Unless you have evidence to the contrary (and I'm sure we'd all like to see that), I don't believe it's possible for Soundforge to do what you say--WITHOUT reencoding the mp3.

Now, IN THEORY, it ought to be possible for an mp3 parser to see only the packets for each channel and reroute them to a new file, with new channel flags inserted. This would change the file, but not the payload data stream itself (at least for that channel). Problems would arise if using shared bitrate allocation, because then the remaining bitrate setting might not fit into one of the Legal choices.

Still, nobody has yet created such an app that I know of...(any takers?)

Scott
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moviebuff2 · Member Joined: 21 Feb 2002 Location: United States