One audio channel ahead another

[Yur22]

After encoding mpeg file in TMPENg Plus the sound became distorted from the middle of the movie. I de-multiplexed mpeg file and loaded mp2 to Sound Forge. I can notice that from some point the left audio channel is little bit ahead of the right one, which creates dissonance. I wanted to cut part of the left channel to equal channels but Sound Forge doesn't allow to cut one stereo channel. Can anybody tell me how to fix that problem?

[Roderz]

Just drag the offending channel onto the blank work space an SF should give a new mono channel, edit + add empty space at end and rejoin.

[Yur22]

Thanks. But how to rejoin channels?

[Roderz]

But how to rejoin channels?

On the (mono) chanel your editing once finished click on properties and there should be an option for stereo, this should give a second empty channel, then drag the good channel from the origanal file to this.
(havent got SF loaded here so I'm working from memory here - used SF4)