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Topic: split stereo file to 2 mono files (Read 8782 times) previous topic - next topic
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split stereo file to 2 mono files

Hi all
is it possible to extract individual channels from a stereo mp3 stream and save them to the new files (file per channel)?
in other words can stereo mp3 file be separated to 2 mono streams?
if yes what software can I use for this?
Is this a lossy operation?

split stereo file to 2 mono files

Reply #1 –
I can't see how this could be done losslessly unless the mp3 was pure dual channel, which they most likely aren't.  I'm also not aware of a program that can do this.
Nero AAC 1.5.1.0: -q0.45

split stereo file to 2 mono files

Reply #2 –
First you decode to wav. This does not lose anything. Of course it does not gain back the resolution lost during the initial encoding to mp3, but nothing more is lost over the mp3 itself.

Open the file in virtually any audio editor. I use CoolEdit/Audition but the functionally you need is a basic editing requirement, so it should be widely available. Select one channel, do a 'save selection' to a new file. Select the other channel, etc.

split stereo file to 2 mono files

Reply #3 –
hm. opening the file in audio editiing software like cool edit or audition is is possible but its not lossy. There is another MP3 encoding required.
So acording to the 2nd post in this threat it is inpossible.

split stereo file to 2 mono files

Reply #4 –
I don't know what you mean by "There is another MP3 encoding required." If you are saying you want to return the two mono files to mp3 when finished, it is true that encoding to mp3 is lossy. However, that has nothing to do with the question as posed.

You can get two mono files in the manner I described. There will be absolutely no loss relative to the mp3 you start with. Loss will only occur if you re-encode the results. That should not be assumed audible. Only experimentation can tell you that.

split stereo file to 2 mono files

Reply #5 –
some one of us does not understand the other side. Almost every audio editor I know converts MP3 to wav then allows user to apply some processing and then one can save results into MP3 file. This saving is another encoding.

split stereo file to 2 mono files

Reply #6 –
AndyH-ha means you don't have to save the results into new MP3 files. You can always save the results as .wav files.

--pv--, you didn't rule that out in your first post.

split stereo file to 2 mono files

Reply #7 –
--pv--, I am curious what you were hoping to achive.  Was this a 'just so I know how' type question, or is there some end result you are trying to get to in which you need to split a stereo file into 2 mono files?
Knowing this might help.  As mentioned before, I don't think it's possible so shave off the left channel bits of an mp3 into a new file, and the right channel bits into a new file. (i could be wrong, i dont know much about mp3 bitstreams  )
Vorbis-q0-lowpass99
lame3.93.1-q5-V9-k-nspsytune

split stereo file to 2 mono files

Reply #8 –
Quote
some one of us does not understand the other side. Almost every audio editor I know converts MP3 to wav then allows user to apply some processing and then one can save results into MP3 file. This saving is another encoding.
[a href="index.php?act=findpost&pid=359196"][{POST_SNAPBACK}][/a]


Switch the type under "Save As" to wav and it will be lossless.

split stereo file to 2 mono files

Reply #9 –
ok guys lets start again from the absolute beginning. I tryed to generalize my situation and put a question but now we all can see that it is very hard to raise a clear question which all the possible readers can interpred the same way.
I recorded a MP3 stream which sounds mono but parameters are set to stereo. To be more precise mp3 112 kbps stereo. Now I would like to know if there is any method to make this file a mono file to decrease bitrate. Teoreticaly 112 kbps of stereo mp3 stream is equal (counting the bitrate) to two mono channels with 56 kbps.
So input is a mp3 file and output is also a mp3 file here. I see it does not make sense whe the original file is encoded as stereo and it also sounds so.

split stereo file to 2 mono files

Reply #10 –
Quote
ok guys lets start again from the absolute beginning. I tryed to generalize my situation and put a question but now we all can see that it is very hard to raise a clear question which all the possible readers can interpred the same way.
I recorded a MP3 stream which sounds mono but parameters are set to stereo. To be more precise mp3 112 kbps stereo. Now I would like to know if there is any method to make this file a mono file to decrease bitrate.


If you encoded it as Dual Stereo, the MP3 is just two seperate MP3 mono streams, and theres probably software that can demux them.  If you used Full or Joint stereo, theres very little wasted space (almost none in Joint Stereo which is probably what you used), so theres probably no need to convert them.

Quote
Teoreticaly 112 kbps of stereo mp3 stream is equal (counting the bitrate) to two mono channels with 56 kbps.


Only in dual stereo mode.  Otherwise this is not true, and no one ever uses dual stereo mode since encoding the entire audio stream twice is a huge waste of bitrate.

split stereo file to 2 mono files

Reply #11 –
This is quite a different question than it first appeared. for one thing you don't now appear to have any interest in the two mono files you first mentioned, you just want to reduce the size of your file by not allowing stereo information.

First, the audio "sounds mono" to you. If that because the two original channels were really identical, or because it just doesn't "sound" much like stereo? I work on old recordings quite a bit. Some are "stereo" but have very little difference between the channels. I make lossless compressed back-up when I'm done. For a recording of this type the final compressed size is much smaller than a same sized recording that really has a great deal of difference between the channels (but still a bit larger than one that is truly completely mono).

Isn't mp3 encoding likely to be the same? If there is little or no difference between the two input channels, should mp3 encoding not recognize that fact and make use of it? In other words, if you had explicitly set it to mono to begin with it might not have made much difference in the file size you have now.

split stereo file to 2 mono files

Reply #12 –
Perhaps (probably!) a tenuous link, but I've just seen this which claims: "Extra Boy Pro (name derived from 'Extract') is a tool that can be used to isolate, remove, suppress or enhance ANY part of a stereo audio track!"

It won't do it on an mp3 (natively anyway), and doesn't answer --pv--, but I saw it and thought of this thread.

There's a lesser functionality/free version here.

split stereo file to 2 mono files

Reply #13 –
Quote
... but now we all can see that it is very hard to raise a clear question which all the possible readers can interpred the same way.
[a href="index.php?act=findpost&pid=359449"][{POST_SNAPBACK}][/a]

I don't think it's hard. Just be more precise next time

Quote
I recorded a MP3 stream which sounds mono but parameters are set to stereo. To be more precise mp3 112 kbps stereo. Now I would like to know if there is any method to make this file a mono file to decrease bitrate. Teoreticaly 112 kbps of stereo mp3 stream is equal (counting the bitrate) to two mono channels with 56 kbps.
So input is a mp3 file and output is also a mp3 file here. I see it does not make sense whe the original file is encoded as stereo and it also sounds so.
[a href="index.php?act=findpost&pid=359449"][{POST_SNAPBACK}][/a]


and by stereo you mean ? it's two channels or simple stereo instead of joint stereo ?

case1 (simple stereo or dual channel):
It's possible (theoretically) to extract both coded channels seperately to mp3 files in a lossless manner. If they are really the same you can safe 56 kbps.

case2 (joint stereo):
joint stereo is supposed to exploit such redundancies. So, if the seperate channels contain really the same signal it's very likely that the encoder used mid/side coding (a joint stereo tool) for every frame where M is the mono-downmix and S the channel difference. Bad news: you can't extract losslessly L and R each to a mono mp3 stream. Good news: You don't have to, 'cause there won't be an advantage since most of the bits are used to represent the M channel (nearly 112 kbps). You CAN extract the M channel (theoretically) but you still need around 112 kbps for that to be lossless.


What do we learn ? Simple stereo is not as smart as joint stereo can be.


Sebi

split stereo file to 2 mono files

Reply #14 –
Quote
I don't think it's hard. Just be more precise next time

OK I'll try my best I can then.

Quote
and by stereo you mean ? it's two channels or simple stereo instead of joint stereo ?

When I am looking up the MP3 info in winamp or foobar I see it is stereo (not joint stereo).

Quote
case1 (simple stereo or dual channel):
It's possible (theoretically) to extract both coded channels seperately to mp3 files in a lossless manner. If they are really the same you can safe 56 kbps.

According to the information provided by winamp and foobar this is my case. But you said it is possible theoretically. Does it mean it is not implemented in any software at the moment?

split stereo file to 2 mono files

Reply #15 –
Yes, it's possible but very likely that no such software exists.

Sebi

split stereo file to 2 mono files

Reply #16 –
Quote
Yes, it's possible but very likely that no such software exists.

Sebi
[a href="index.php?act=findpost&pid=359933"][{POST_SNAPBACK}][/a]

Can you recommend any way to go? or its not possible for an ordinary guy?

split stereo file to 2 mono files

Reply #17 –
Sorry, I guess there's nothing you can do. Just leave your mp3 the way it is. I don't think any 'coding action' is worth the trouble unless it's a matter of life and death.

Sebi

split stereo file to 2 mono files

Reply #18 –
If you have a audio editor, or can afford a little time to learn to use one of the free ones like Audacity, why not just find out what you can do. If I were interested in this  question for any audio data I have, I would have just done what I described in my first post and been done with it. I would know if there is any significant storage saving by looking at the final file size. I would compare the 'mono' version with the original in WinABX or PCABX and quickly find out if I could tell any difference between them.

Of course if I was mainly interested in the theoretical consideration "is the quality degraded" I guess this might be a little more difficult. How the heck do you define quality if it isn't what you hear? When dealing with an uncompressed original recording, it might be taken to mean that an uncompressed copy matches the original exactly, bit for bit, but that kind of technical comparison really isn't possible for any grade of lossy compression anyway.

Re-encoding an mp3, at the same or at a different bitrate, might be said to degrade the audio quality, but that does not necessarily mean that you would ever be able to hear any difference, no matter how long or how intently you tried. Depending on the parameters of the second encoding you could end up with something that sounds very different, but since you won't be trying for that kind of result, why not just find out what you can accomplish, for a lot less energy than it takes to agonize over it?

split stereo file to 2 mono files

Reply #19 –
What the OP appears to be requesting is a way to turn his stereo 112Kbps files into something lower than 112Kbps (he claims his intent is a smaller file size). What is the problem with simply transcoding the files? I can't believe any quality difference due to transcoding would be noticed at a miserable sub 112Kbps rate.
Who controls the past controls the future: who controls the present controls the past

split stereo file to 2 mono files

Reply #20 –
So no one knows of a tool that can split full stereo mp3's into separate mp3's for each channel, losslessly?

I have some gigabytes of files that are encoded from pure mono into full stereo, 192 and 256 kbps.  I would very much want to cut them down to half the size with exactly the same quality...

split stereo file to 2 mono files

Reply #21 –
Some time ago, before ever hearing of LAME, I encoded a fair number of speech only files as CBR stereo at  160kbps. The files were "stereo" only because such audio on either cassette or CD is dual channel. The audio was in fact mono.

Later, having a little better understanding of mp3 and knowing about LAME and VBR, I tried decoding some of them, then encoding only one channel to a VBR setting decided upon after some experimentation (I tend to favor WinABX). While this might have resulted in some infrequent instances of reduced quality for a word or two here and there, the only thing I'm certain about is that I saved a lot of disk space and everything sounds the same as before to me.