converting audio track to a backing track? -Sound Forge - PC

Subject:converting audio track to a backing track? Posted by: scarab12 Date:3/30/2004 7:14:31 AM I am trying to use the following procedure to produce a backing track from an audio file. 1. reverse the phase of the left channel by using invert 2. mix both channels into a single channel ( mono ) 3. split the single channel audio file back into a stereo file 4. reverse the phase of the left channel back again using invert. Using channel convert I invert the audio file, then using channel convert again I then convert stereo to mono but this is where I run into a problem. The wave form disappears from the display. The file will not play and if I try to open the audio file again it states the file is already open? I'm missing something simple here but can't figure it out. Any help would be very much apreciated. It's Sound Forge 6 build 132
Subject:RE: converting audio track to a backing track? Reply by: Chienworks Date:3/30/2004 8:44:38 AM The problem you have is that you are inverting both channels. You need to select only one channel before inverting. Step 3 is unnecessary and accomplishes nothing. Step 4 will put the two (identical) channels out of phase and you'll suffer massive cancellation depending on your speaker placement. Stop at step 2 with the mono file and you're as done as you can be.
Subject:RE: converting audio track to a backing track? Reply by: scarab12 Date:3/30/2004 8:51:06 AM Thanks kindly, your advice and solution is appreciated.
Subject:RE: converting audio track to a backing track? Reply by: Rednroll Date:3/30/2004 6:00:22 PM It's doing exactly what you told it too. "3. split the single channel audio file back into a stereo file" The math is "Left=L" and "Right=L" doing this. "4. reverse the phase of the left channel back again using invert." Now the math becomes "Left=(-)L and "Right=L". "5.Using channel convert I invert the audio file," Now the math becomes "Left=L" and Right=(-)L" "6.using channel convert again I then convert stereo to mono" Now MONO is Left+Right= L+(-)L=0 A negative plus a positive of the same magnetude still equals zero. A little algebra at work.

Subject:converting audio track to a backing track?

Posted by: scarab12

Date:3/30/2004 7:14:31 AM

I am trying to use the following procedure to produce a backing track from an audio file.
1. reverse the phase of the left channel by using invert
2. mix both channels into a single channel ( mono )
3. split the single channel audio file back into a stereo file
4. reverse the phase of the left channel back again using invert.
Using channel convert I invert the audio file, then using channel convert again I then convert stereo to mono but this is where I run into a problem. The wave form disappears from the display. The file will not play and if I try to open the audio file again it states the file is already open? I'm missing something simple here but can't figure it out.
Any help would be very much apreciated. It's Sound Forge 6 build 132

Subject:RE: converting audio track to a backing track?

Reply by: Chienworks

Date:3/30/2004 8:44:38 AM

The problem you have is that you are inverting both channels. You need to select only one channel before inverting.

Step 3 is unnecessary and accomplishes nothing. Step 4 will put the two (identical) channels out of phase and you'll suffer massive cancellation depending on your speaker placement. Stop at step 2 with the mono file and you're as done as you can be.

Subject:RE: converting audio track to a backing track?

Reply by: scarab12

Date:3/30/2004 8:51:06 AM

Thanks kindly, your advice and solution is appreciated.

Subject:RE: converting audio track to a backing track?

Reply by: Rednroll

Date:3/30/2004 6:00:22 PM

It's doing exactly what you told it too.

"3. split the single channel audio file back into a stereo file"

The math is "Left=L" and "Right=L" doing this.

"4. reverse the phase of the left channel back again using invert."
Now the math becomes "Left=(-)L and "Right=L".

"5.Using channel convert I invert the audio file,"
Now the math becomes "Left=L" and Right=(-)L"

"6.using channel convert again I then convert stereo to mono"

Now MONO is Left+Right= L+(-)L=0

A negative plus a positive of the same magnetude still equals zero. A little algebra at work.