Removing background music

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Removing background music

Postby Sierra Lorna » Thu Aug 01, 2002 9:11 pm

I'm trying to do voiceovers for my video but there's music in the background that's very distracting. Is there anything I can do to get rid of it?
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Postby klinky » Thu Aug 01, 2002 9:55 pm

What do you mean by music in the background?

Is it in the original soundtrack? (just delete the audio from the footage)

or from the voice over audio (redo voice over w/o annoying music in background).




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Postby trythil » Thu Aug 01, 2002 9:58 pm

Or is there a vocal part in the music that you're using that you'd like to strip out the background instrumentals?

If that's the case, you're in for a chore -- it's very difficult to do that without having access to what would amount to the original (e.g. direct-from-the-studio) recordings. There are methods that can isolate a piece of the waveform (typically the frequencies used for human speech) and reproduce that to an audio file, but they tend to not work all too well without some major clean-up work.
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Postby Sierra Lorna » Thu Aug 01, 2002 10:41 pm

or from the voice over audio (redo voice over w/o annoying music in background).

Yeah, that's what I meant.

If it's possbile, I'd like to try it but if it's not really worth it, I might be able to just leave it in. I'd really like to take out the stupid music though...
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Postby klinky » Thu Aug 01, 2002 10:56 pm

Sierra Lorna wrote:
or from the voice over audio (redo voice over w/o annoying music in background).

Yeah, that's what I meant.

If it's possbile, I'd like to try it but if it's not really worth it, I might be able to just leave it in. I'd really like to take out the stupid music though...


It's possible, but I bet it's tricky.

I would not know where to begin or what tools to use..

It'd be kind of like trying to edit a person who is standing in front of another person out of the image, then redrawing the person in the background by hand. It'd be that pain-in-the ass like. Since you're most likely going to loose some quality and it's going to take out some of the important data as well as the annoying music.

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Postby SephirothJenova » Thu Aug 01, 2002 11:04 pm

Can't you just turn up the treble and turn down the bass? That's what I do in the car, and it works fine. You can still here a few spots and stuff, but the majority of it is alright.

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Postby Zarxrax » Thu Aug 01, 2002 11:47 pm

Just play with the equalizer. You cant remove the music really, but you can minimize it.
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Postby jbone » Fri Aug 02, 2002 12:07 am

SephirothJenova wrote:You can still here a few spots and stuff,


You can still <I>where</I> a few spots and stuff?
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Postby trythil » Fri Aug 02, 2002 12:22 am

Sierra Lorna wrote:
or from the voice over audio (redo voice over w/o annoying music in background).

Yeah, that's what I meant.

If it's possbile, I'd like to try it but if it's not really worth it, I might be able to just leave it in. I'd really like to take out the stupid music though...


-- Disclaimer: I am not a DSP or acoustics engineer, yet :P , so some of this could easily be wrong --

It is possible, but as I said before, you'd have to isolate the frequencies that you want. (In this case, the voices.) Then, as it's highly likely that an instrument playing will be at the same or similar frequency you're capturing, you have to know the exact acoustic characteristics of that instrument you're trying to eliminate (for example, the harmonics of the instrument, which is what lends musical instruments their unique sound anyway.)

You must then do this with doing as little damage to the vocal waveforms that you want to extract; if you do damage those you have to re-construct them.

It's hard, and I'm willing to bet that the way most DJs do that kind of sampling is either by amplification of that human-vocal range so that it effectively drowns out the background enough, or by contacting studios for the original multi-track data.
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Postby AbsoluteDestiny » Fri Aug 02, 2002 1:36 am

OK, as nobody has mentioned it I think I'll talk about how karaoke filters work.

It's a common misconception that they just get rid of certain frequencies. You'll find that a lot of musical instruments, incuding vocals, occupy the same frequency ranges and that harmonics also spread different elements of the instrument/vocals across such a wide range that it is difficult to single out one frequency to eliminate.

However, what happens is that when a song is recorded, generally the vocals are given the exact same intensity on both the left and right channels. This means that what you can do is take the Difference of the two channels (make the left channel = left-right and make the right channel = right-left) and then you have the voice removed, for the most part (except for echoes).

So, in order to single out your music, you need to do an extra step which is original music - voiceless version. You have to do this for each channel independantly.
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Postby Metro » Fri Aug 02, 2002 1:38 am

Since Anime likes to reuse music, would it be possible to find a solo clip of the music and "subtract" it from the music+vocal clip? I have no idea what type of software/filters would do this but I think it should work.

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Postby trythil » Fri Aug 02, 2002 2:06 am

AbsoluteDestiny wrote:OK, as nobody has mentioned it I think I'll talk about how karaoke filters work.

It's a common misconception that they just get rid of certain frequencies. You'll find that a lot of musical instruments, incuding vocals, occupy the same frequency ranges and that harmonics also spread different elements of the instrument/vocals across such a wide range that it is difficult to single out one frequency to eliminate.

However, what happens is that when a song is recorded, generally the vocals are given the exact same intensity on both the left and right channels. This means that what you can do is take the Difference of the two channels (make the left channel = left-right and make the right channel = right-left) and then you have the voice removed, for the most part (except for echoes).

So, in order to single out your music, you need to do an extra step which is original music - voiceless version. You have to do this for each channel independantly.


Yes, but see, that's assuming you -have- the instrumentals. For a lot of songs, that just doesn't exist (though there ARE a few for which instrumental versions DO exist; in that case, sure, you're in luck).

Without that extra data you're forced to do with what you have, and that's why I said it was extremely difficult above. :)
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Postby AbsoluteDestiny » Fri Aug 02, 2002 2:23 am

Um... did you actually read what I said?

You dont need the instrumentals. You just have to single out the parts of the waveform that have the same intensity in each of the stereo channels. That's how karaoke filters work.
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Postby trythil » Fri Aug 02, 2002 3:38 am

AbsoluteDestiny wrote:Um... did you actually read what I said?

You dont need the instrumentals. You just have to single out the parts of the waveform that have the same intensity in each of the stereo channels. That's how karaoke filters work.


Alright, reread it, noticed one paragraph of mine unnecessary, new rebuttal:

Yes, that's how karaoke filters work. But this isn't karaoke. Vocals are not always recorded with equal intensity on all channels*. I don't think you can assume that whatever music Sierra Lorna is trying to extract vocals from has that characteristic. (She is trying to extract vocals, from what I understand...)

* For a good example, listen to Kraftwerk's "Sex Object", the Spanish version. The vocals travel from left to right and back again in the first 7-8 seconds, and they do that occasionally through the rest of the song.

If you have the instrumentals + vocals and they are all identical except where there is vocal data present (e.g. no lossy compression), you can perform some bit-juggling there.
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Postby AbsoluteDestiny » Fri Aug 02, 2002 3:41 am

Yes, I know not all vocals are recorded like this.

But this is a voiceover - it's blatantly going to be all centre channel so the principle should work pretty well.

Once you have the track without the vocals you use that version to subtract the music from your original track, like I said.

It should be pretty easy with a decentish wav program to make a vocal-less version and then subtract it from the original.
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