Audacity Forum

android927 wrote:

RamonFHerrera wrote:

steve wrote: The only explanation that I can think of is that they are NOT IDENTICAL (though they may be extremely similar). For cancellation to occur the audio samples must be exactly the same value at exactly the same time but with reverse polarity.

Steve,

You have to use an application that aligns the signals at the millisecond -or rather: sample- level. As you correctly stated, once that is done, the phase/shift between the 2 signals becomes zero and the subtraction is trivial.

I know of at least one application, and am looking for others as we speak (in 2015). To posters johnrichki, Loonwolf and any other forum participants interested: please send an e-mail to ramon at patriot dot net for the name of the free application since I have been sternly warned to "cease and desist" from mentioning any non-Audacity products, in these otherwise outstanding forums.

Regards,

-Ramon

So since it seems that the whole cease and desist thing was just a misunderstanding, can you please post the name of that program now?

The name was already given. And I see no reason to withhold a link http://www.libinst.com/Audio%20DiffMaker.htm. What Steve was saying is that app would not help the user we were trying to help.


Gale

As has been posted before, cancellation techniques almost never work because the two files do not contain identical works and that can be traced to a pass through compressed formats such as MP3.

MP3 gets its small file sizes by creating cleverly hidden sound damage and the process depends on content. If you have an MP3 track with violins, trumpet and drums and a second MP3 track with the drums taken from the exact same performance, the two drum tracks are different.

The effect is significant. There is a technique in AudioBook production where you intentionally create sound files a bit "off" such that the conversion to MP3 and resulting changes don't violate publisher's standards.

Koz