Universal's Audible Watermark

This is my personal blog. The views expressed on this page are mine alone and not those of my employer.

Update, April 8, 2013: Can you hear it? Take a watermark listening test.

A while ago, I wrote about my confusion regarding Weird Spotify Compression Artifacts. It turns out the artifacts I was hearing are not due to compression, but a result of audio watermarks that Universal Music Group embeds in digitally distributed tracks. This watermark is embedded in UMG tracks on Rdio, Spotify, iTunes, Amazon, and others. The watermark can also be heard in Universal tracks broadcast over FM radio. Universal Music recordings make up about 25% of most online catalogs, and its labels include Interscope, The Island Def Jam, Universal Republic, Verve, GRP, Impulse!, Decca, Deutsche Grammophon, Geffen, etc.

What the watermark sounds like

Spectrogram of the difference between a watermarked and unwatermarked UMG track. The energy is concentrated in two bands between about 1 khz and 3.5 khz - where the human ear is most sensitive.

UMG uses a spread spectrum watermark, a technique explained in detail in this Microsoft research paper. The watermark scheme modulates the total energy in two different bands, 1khz to 2.3 khz and 2.3 to 3.6 khz. The energy is concentrated in the most perceptually sensitive frequencies because that makes it more difficult to attack or remove without significant audible distortion.

The energy is increased or reduced in 0.04 second blocks. The result can be characterized as a fluttering, tremolo sound. Listen closely to the original vs. watermarked audio samples and try to focus on the 1 khz to 3.6 khz noise range. It helps to wear headphones in a quiet environment.

Audio samples

Here is a short sample (excerpt: Three Doors Down - When You're Young). These are lossless original and watermarked files; what you hear is not a result of compression.

Original:

Watermarked:

If the difference between the two isn't clear, here it is by itself:

Difference:

The character of the watermark may seem subtle during this short sample, but through the duration of an entire song it becomes more familiar and more annoying. Check out my original post on the subject for more examples.

Technical details

The watermark does not start until 1 second into the audio. After this the signal is divided into 0.08 second blocks. Each block is divided in two: some amount of energy is added to the first half and the same amount is subtracted from the second half. This coding scheme allows blind detection (without access to the original file). The actual information in the watermark is not easily recovered because it is modulated by a pseudo random sequence, which is generated by a secret key.

I did a little searching and it seems this watermarking technology is provided by MarkAny, a Korean company that has developed their own watermarks out of university research, and purchased some watermarking patents from Digimark.

Removing the watermark

Since the watermark creates audible distortion, it's worthwhile to try to reduce it. I wrote a MATLAB script that analyzes the block energy and applies some smoothing. This is the result:

Watermarked:

Restored:

More discussion

Hydrogenaudio forums on watermarking

UMG Watermarks audiophile files, pisses off paying customers

Why do labels watermark tracks? Watermarking simplifies copyright enforcement by letting a company track music on peer-to-peer networks. "It gives them the ability to put pressure on policy makers and ISPs to do filtering," says Fred Von Lohmann, an Electronic Frontier Foundation attorney. That may be about the best explanation you will find. See DRM Is Dead, But Watermarks Rise From Its Ashes

Most listeners probably don't notice the watermark in the music they listen to. The audibility of the watermark is very content-dependent; classical, and solo piano in particular, are affected most severely. I've seen complaints on classical music forums with descriptions calling out the characteristic fluttering of the watermark. These listeners might be acutely aware of these sound quality problems, but blame lossy compression or streaming services.

I don't think there is anything inherently wrong with watermarking. The problem is with this particular poorly tested implementation. It is unfortunate considering the amount of engineering effort that goes into every music production.

35 ResponsesLeave a Reply

  1. Alex Jimenez

     /  February 4, 2012 Quote

    Thank you for figuring this out. I use Spotify and like many had thought something was wrong with the streaming codec. It's also being used on iTunes, judging by a recent LA Philharmonic download of Wagner excerpts--the irritating flutter is there too.

  2. Taylor Perkins

     /  June 12, 2012 Quote

    This is great analysis.

  3. bozmillar

     /  September 10, 2012 Quote

    I've been wondering what this flutter was for a long time. Thanks for putting this up. I always just figured it was a compression issue, but when I upgraded spotify to the "high quality streaming" and it was still there, I got suspicious and found this.

  4. Hi;

    How did you obtain a difference wav ? What tool did you use ? I have a CD and an official download and wanted to check for myself.

    Thanks;

    George

  5. Kasper Holbek Jensen

     /  October 4, 2012 Quote

    Very nice brief analasys for non-soundtechies like myself, I was wondering if the smoothing script is of up grabs. Or would that violate some term/law?

  6. I didn't post the script since distributing it would probably violate the DMCA, but it is pretty easy to duplicate if you know how to work with audio in the frequency domain...

  7. I generated the difference audio by aligning the signal of the original and watermarked audio and subtracting them. You can do this in any wave audio editor like Audacity or Adobe Audition, but the sample alignment is the most important part.

  8. Kasper Holbek Jensen

     /  October 5, 2012 Quote

    I wouldn't know where to start. It is a strange thing that the real quality audio is now reserved for the pirates. This industry really knows how to hit a target.

  9. B. B. Pedersen

     /  May 13, 2013 Quote

    Thanks, shared.

  10. George W

     /  May 13, 2013 Quote

    I think they thought they were really clever this time. Since virtually all music consumption today is via online listening, (read Youtube &Co) so people neither notice nor care.

    Most of the few who actually pay for music are playing it through the laptop USB speakers, (read Spotify &Co) which often aren't exactly HIFI. And most grown-ups don't hear the difference anyway. (I tested the given samples with Sony headphones. And my hearing is flat to a 12kHz personal cutoff, which is average for my age.)

    So, the only ones to really suffer must have good hearing and a proper stereo set. But many of them do actually buy CDs, so that's even better for the industry. :-/

    Now, I do agree about watermarking in general. I think it is OK to watermark your intellectual (or alas, your artists' intellectual) property, but it shouldn't degrade paid-for music.

    At any rate, this is a step towards sanity compared to copy protection. I think we are on our way to a better future because every year an old boss retires, and instead comes a younger one, who's presumably seen computers as a child.

  11. George - I want to offer a small counterpoint to a few of your statements. It might be that listeners with poor hearing or cheap stereos actually hear the watermark more prominently. Consider that a cheap stereo system will have a low and high frequency roll off, such that only the midrange is left over; the watermark is concentrated in the middle, unaffected. However, played over a hi-fi system, there's more energy in the highs and lows, and that's just more energy that might mask the watermark in the middle. Likewise, for someone with some hearing loss, unless their hearing loss lands right on 1 to 3.6 kHz, they're simply going to be deaf to acoustic energy that would otherwise serve to mask the watermark.

  12. Pål Bråtelund

     /  May 15, 2013 Quote

    Thanks for this analysis, Matt. All this is in a lossless domain - got any thoughts on how the most popular codecs (AAC, Vorbis and MP3) reacts to spread spectrum watermarks?

  13. Pål Bråtelund: Thanks for this analysis, Matt. All this is in a lossless domain - got any thoughts on how the most popular codecs (AAC, Vorbis and MP3) reacts to spread spectrum watermarks?

    The watermark is designed to withstand lossy compression. You'll still be able to hear it in a 64 kbps MP3, for example.

  14. Thanks a lot for the info given here.

    I recently subscribed to Qobuz because they are the only ones who stream lossless. However, the Universal tracks do have the digital watermark. Listen to the first seconds of Shostakovich's 8th symphony conducted by Valery Gergiev (Philips). It's simply unlistenable. I'm not willing to pay for audio that is degraded in such a way. Bad for Qobuz which is really a great site otherwise.

  15. Sorry. I have to correct my statement above about watermarking at Qobuz.

    I bought one track I had on CD (Track 1 of Boulez' Miracoulous Mandarin on DG). I did an inverted mix paste, and the result was digital silence. So obviously they were bit-identical. So at least with this one example, there is no digital watermarking of Universal tracks at Qobuz.

    Maybe the Gergiev is just a crappy recording (I can't compare).

  16. Kevin E

     /  July 16, 2013 Quote

    Thanks for this! I can't believe there hasn't been more uproar over this. There is an Avett Brothers single on the radio these days that has such horrendous watermarking that I want to rip my hair out every time i hear it.

    If anything, watermarking will just incite more piracy. From now on, I certainly won't buy anything under the UMG umbrella on Amazon or iTunes.

  17. What's the name of the piece in the first audio example of your A-B test?

  18. It is by Ravel. Daphnis et Chloe - Troisième partie (Part 3) - I. Lent.

  19. Matt: It is by Ravel. Daphnis et Chloe - Troisième partie (Part 3) - I. Lent.

    Thanks!

  20. So that's why some songs on the radio (and played by less classy wedding DJs :D) have sounded so crap of late...

  21. frodowiz

     /  November 19, 2013 Quote

    freedom isnt free. if no one bought music from distributors who watermark, AND let them know why, and demanded money back for distorting their music purchase. you get the idea.. people can complain all they want but big industry is only going to get worse, more greedy. however, you can count on greedy business to do whatever they need to do to maximize profits and that means no watermarks if no money is made from them. with the current dictatorship here in america run by the entertainment giants, you are in for a long fight.

    barring that, here is my other suggestion. develop software that writes watermarks in the same fashion as the watermarks you are trying to remove. use this software to write new watermarks. various tweaks, namely phase change for the method above and other tweaks for other methods. the idea is to erase, or minimize or overwrite(depending on type) the added watermark enough it fails at its original purpose. this isnt so difficult to conceptualize and a case can be made for removing the watermark as it borders on malware in part by allowing other code on websites for instance or media players to target ads at you. it is malware. but sadly, while the author of the site and a few others do their share in educating, the masses still go back for good kick in the a** only to send the message to the music industry that they are willing to put up with it. yes, shake your fists and type at the top of your lungs friends. no hurry and grab lady gaga's latest.

  22. dual lufsig

     /  December 25, 2013 Quote

    Fuxk UMG.
    Some suggestion on the listening test: Some type of music (piano) can easily reveal the watermark while some (fast/percussive/loud) are much harder to identify that I actually gave up testing. It's better to add an "I can't hear" option to make the statistics more useful. Also, can you publish your statistics to show which music clips have the highest identification rate? Thanks.

  23. Bucket O'Toules

     /  January 1, 2014 Quote

    frodowiz: freedom isnt free. if no one bought music from distributors who watermark, AND let them know why, and demanded money back for distorting their music purchase. you get the idea.. [[SNIP]] yes,shake your fists and type at the top of your lungs friends. no hurry and grab lady gaga's latest.

    This entire post. Yes. Unless we hit them in the pocketbook. Good luck on that because certain demographics only care about the hype that the record companies and other big industry creates. Without thinking and nearly as a majority bloc, they buy into the bling, the rims, the grills, the twerking, the stupid antics, and other "culture" and prop up the corporations. We were given brains for a reason, and unfortunately, a majority of the population still operates on a base, animal level. Big Industry, as a creature of its own, adapts easily to this highly positive reward/response cycle.

    So ... unless we stop consuming ... we will have to suffer for our pleasures.

  24. Philly Bob

     /  January 13, 2014 Quote

    Verance has one also that was used in the MLP section of DVD-Audio discs.
    It's purpose was to prevent copying of the discs.
    When a copied disc was played in a unit that detected the watermark, the playback would halt after 15 or 30 seconds.
    This watermark too, was noticeable.
    It is reported that it too, was able to be beaten.

  25. John Kristian

     /  February 24, 2014 Quote

    Thank you for a very good summary.
    I was wondering if you could analyze this track:
    http://open.spotify.com/track/439riMf3Je9jTGdLQ1xDBd

    It has noise at a very low frequency that makes your subwoofer/bass "pulsate" constantly. It's easier to see it on your woofer than to hear it. It's a bit scary when you're playing at high volume, you might reach your drivers XMAX.

    I don't know if this is a bug in the mix or a watermark. It's the same phenomenon on both spotify and Wimp HiFi (lossless)

  26. John Kristian

     /  February 24, 2014 Quote

    I scored 15/16 on the watermark test on the first try (track 12 was difficult). I'm astonished how bad this watermark affects the sound quality.
    A half bad MP3 rip would often sound better. It's clear and simple fraud if you ask me.

  27. John Kristian: I scored 15/16 on the watermark test on the first try (track 12 was difficult). I'm astonished how bad this watermark affects the sound quality.
    A half bad MP3 rip would often sound better. It's clear and simple fraud if you ask me.

    Hi John, the tracks are randomized, but you're probably talking about one of the electronic tracks. The audibility of the watermark is very content-dependent. Solo piano and classical are affected most severely.

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