Competition: Find the hidden music.

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Competition: Find the hidden music.

Permanent link to this post Posted by steve » Mon Aug 29, 2016 10:22 pm

There are two “hidden” tracks within this track: https://dl.dropboxusercontent.com/u/611 ... racks.flac Can you find them?

Prize:
This is just for fun, so let's have prizes for everyone :)
As soon as someone, anyone, succeeds in separating the two hidden tracks, the Audacity plug-in used to make (and extract) these hidden tracks will be made available for free download.

How to enter:
Have a go at extracting the two hidden tracks. If you manage to do it, upload an extract of each hidden track and post a link to your tracks as a reply to this facebook post: https://www.facebook.com/AudacityTeamOf ... 0582738366
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Re: Competition: Find the hidden music.

Permanent link to this post Posted by 2xyassin » Thu Sep 08, 2016 11:07 pm

I see that some people managed to find the hidden audio in the file. I would love to know more about how they did it !
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Re: Competition: Find the hidden music.

Permanent link to this post Posted by cyrano » Thu Sep 08, 2016 11:20 pm

Yep. Me too, as I can't even read that faecsebook page... :cry:
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Re: Competition: Find the hidden music.

Permanent link to this post Posted by Robert J. H. » Fri Sep 09, 2016 4:18 am

cyrano wrote:Yep. Me too, as I can't even read that faecsebook page... :cry:

I feel with you. My FaceBook page has been compromised last week and all posts and friends--including Steve--are deleted. -Sigh-


As for how it was done:
A first glance at the project rate (192 kHz) suggests that something is hidden in the upper frequencies--Steve is usually not a fan of high sample rates.
Essentially, the hidden tracks could have been added directly in the frequency domain by stacking up 4 FFTs on top of each other.
Looking at the spectrogram reveals two prominent peaks at 30 and 60 kHz.
This excludes spectrum stacking because the energy would be differently distributed.
Therefore, the audio must have been modulated.
I tried FM demodulation, et voila, it worked.
It is good that it wasn't FSK, PSK or something of that sort...
Or a 24 bit audio with three times 8 bit tracks (two hidden as inverse quantization noise).

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Re: Competition: Find the hidden music.

Permanent link to this post Posted by cyrano » Fri Sep 09, 2016 5:22 am

Thanks, Robert.

My FB account wasn't compromised. But I grew tired of getting spam from FB. I demanded to have my account deleted when the spam started getting annoying. And that was when they started spamming me with reminders for dear friends that had passed away years before. When they started censoring all kinds of posts on behalf of dictators all around the world, that was enough insult. It took only four years to get my account closed.

Now I only have to eradicate a Linked In account...
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