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>I don't think there is anything inherently wrong with watermarking. The problem is with this particular poorly tested implementation. There is. Audio watermar

by dTal 5y ago

>I don't think there is anything inherently wrong with watermarking. The problem is with this particular poorly tested implementation. There is. Audio watermarking is inherently audible, because that is the only way to avoid being stripped out (deliberately or inadvertently) by the incredible technology we have for removing inaudible information from audio recordings: lossy audio codecs. The artifacts must be so salient that the codecs deem them important, audible information - codecs designed with elaborate psychoacoustic models, especially to make that judgement call with maximum efficacy. There's no way out.

mixedCase 5y ago
I imagine this could be worked around by using forked encoders that are designed to introduce the watermark when encoding lossy versions. This of course would mean the watermark would not survive transcoding from lossless, but as we can see in TFA the watermark can be made useless all the same without such efforts. With that said the oxygen malpractitioners that run the music industry have never put actual consumers' satisfaction above implementing trivially circumvented security theater, so pirates win all the same in all scenarios.
- mgdlbp 5y ago
  Huh? Couldn't anyone just re-encode the lossy version? Though with some generation loss, since a transparent lossy encoding presumably would also preserve any watermarks.
  - dTal 5y ago
    Yes. The entire supposed value proposition of watermarks is to survive re-encoding / the analog hole.
adrianN 5y ago
If the listener doesn't know the "true" information, it is sufficient if the watermarked version sounds plausibly like a real sound. I think it's too strong to require the watermark to be completely inaudible. It is sufficient if given two recordings of unknown sounds a listener can't tell which one is watermarked and which one isn't.
- greenthrow 5y ago
  As a musician; no. That is not sufficient. Any audible watermark -- and as the grandparent comment correctly points out, that is any that is going to do its job -- is unacceptable. It is modifying what the artist intended you to hear in a destructive way. It is destroying the original performances. This is a terrible practice.
  - kyleplum 5y ago
    Are you against all lossy compression methods as well? The watermark can simply be a slight tweak of the compression algorithm that could as well have been done for non-watermarking reasons.
    - cortesoft 5y ago
      I think the point is that the watermark is supposed to survive being re-encoded, so it can’t be something just in the compression algorithm.
      - kyleplum 5y ago
        There is a discussion to be had around watermarks surviving transcoding but I was mostly trying to understand whether the opinion > It is modifying what the artist intended you to hear in a destructive way. It is destroying the original performances. also applies to lossy encoding.
        dTal 5y ago
        The whole point of lossy compression is that it tries to be inaudible, as a primary concern. The whole point of audio watermarking is that it survives lossy compression. Inaudibility is merely a secondary concern. This is an adversarial relationship, and one that the audio watermarking is doomed to lose. By and large, lossy codecs succeed in transparency, and therefore as an inevitable consequence, watermarking fails at it. After decades of development, lossy codecs are just too good - there's nowhere left to hide information. (It's also worth noting that the consumer benefits from the quality tradeoff that compression makes, in the form of decreased storage and bandwidth. They don't benefit from the audio watermarking at all.)
CharlesW 5y ago
> Audio watermarking is inherently audible, because that is the only way to avoid being stripped out (deliberately or inadvertently) by the incredible technology we have for removing inaudible information from audio recordings: lossy audio codecs. You're assuming that perceptual audio coders do a perfect job at encoding what can be heard* and not encoding what can't be heard*. This isn't true in both directions — they encode detail that can't be heard* in the source, and lose detail that can be heard in the source*. *This is contextual, depending heavily on the listener and the listening conditions.
- dTal 5y ago
  Not a perfect job. But a state of the art job! The relationship between watermarkers and lossy perceptual codecs is fundamentally adversarial - one side trying to eliminate all inaudible information, the other trying to sneak inaudible information past it. And so much more research has been poured into lossy compression, that the watermarkers just can't win. Bear in mind also that the watermark needs to work with all lossy codecs, so the information must be considered salient by all of them. There's just no way to do this inaudibly.
  - karmakaze 5y ago
    I doubt that this is where we are at today. We have higher fidelity transmission compared to a joint-stereo 128kbps mp3, which was probably already enough to carry imperceptible watermarks.
akira2501 5y ago
All major market FM broadcasts in the United States have audio watermarking applied to them, and most likely to their online only streams as well. Do you hear the watermarking in that audio? The system is called CBET and it's based on the psychoacoustic model as well, except it determines the level at which watermark should be injected at. High enough that it passes codecs easily, but just below perception so you generally can't detect the tones that it has added to the audio. The trade is that CBET only moves about 8 bits/second of information through the side channel, which is just enough to push a station ID and timestamp through the channel for Nielsen's ratings purposes.
- dTal 5y ago
  FM radio is a dumpster fire anyway, quality-wise. Apart from the awful dynamic range and noise floor, god knows how many plugins and mp3 re-encodes are used in the average pipeline. So I wouldn't be especially surprised to find that 8 bits/second extra crap on the pile goes unnoticed. However I'm awfully curious about this system, especially "high enough that it passes codecs easily". I would naively expect that to be highly dependent on the codec and bitrate chosen, and further expect the range between "inaudible" and "codec-passing" to be negative for many common untransparent lossy profiles, like 128kbps mp3. Where can I read more?
  - akira2501 5y ago
    It's hard to find information on. The company used to be called "Arbitron" and they filed several patents on the technology, which is where I did most of my research. There are 10 bands, each of which can carry 1 of 18 tones. 16 tones are to signal, so the stream is 4 bits wide, and the other two tones are used as a "STOP" and "SYNC" marker in the data stream. All bands carry identical information, but each bit within a band is encoded with a different tone than any other band. So, it appears random or uncorrelated at first glance, but you can see the pattern pretty quickly if you do a long enough analysis. The same message gets identically repeated 12 to 13 times per minute and the message only changes once per minute. Here's an example isolation of the signal [1]. The coder monitors incoming audio and does a psychoacoustic pass to determine which level the tones should be injected at. If it can't find a good level for a tone, it uses the lowest possible level... which usually works out fine due to the 10 redundant signals in the watermark. Encoders like MP3 see the injected tones as signal and will make the bits available to ensure they're encoded rather than correctly masking them out as non-audible material. The 10 bands help here as well, as even if the encoder fails to code the signal in one band, there's usually enough redundant bands that you can successfully decode the watermark. [1]: https://www.sigidwiki.com/wiki/CBET https://www.sigidwiki.com/wiki/CBET
kurthr 5y ago
I disagree. It depends how many bits you want to encode in what period of time. If you only need 1 bit per second, then it can still be inaudible and not susceptible to _current_ lossy psychoacoustic compression models. Universal was both dumb and greedy (and hopeful?) so they got caught making their music into crap. However, encoding a series of highly discernable tones into the audio is just dumb. Instead they should use phase modulation at low frequencies. Current compression models don't play with subtle changes of meter much, because they mostly use local encoding and there's not much room for improved compression with (non-audible) modulation. Of course, if Universal wanted to be able to accurately detect 5 second clips (rather than 2 minute songs) this would be a lot more difficult... and of course they want every thing, at the expense of listener experience.
karmakaze 5y ago
There's a large gap between audible and detectable. A transmitter could transmit a weak signal in a specific pattern on a number of arbitrary preselected frequencies. They would more-or-less seem like noise lost in the noise floor. Only when you specifically filter for the specific set of frequencies can you discern the pattern that was put there that could not appear by chance. You don't even need to use the same frequencies throughout the transmission. As long as the schedule is decided up-front it can serve like a one-time pad for encryption.
LeoPanthera 5y ago
I am far from an expert in this, but, couldn't you design a watermark that removes certain frequencies in known locations in the spectrum, at known times? Those gaps would obviously stay missing in a compressed version - lossy codecs don't add noise.
montag 5y ago
I didn't say _perceptual_ watermarking, which, as you point out, is at odds with perceptual audio compression... :)

by dTal 5y ago

mixedCase 5y ago

I imagine this could be worked around by using forked encoders that are designed to introduce the watermark when encoding lossy versions. This of course would mean the watermark would not survive transcoding from lossless, but as we can see in TFA the watermark can be made useless all the same without such efforts. With that said the oxygen malpractitioners that run the music industry have never put actual consumers' satisfaction above implementing trivially circumvented security theater, so pirates win all the same in all scenarios.

mgdlbp 5y ago
Huh? Couldn't anyone just re-encode the lossy version? Though with some generation loss, since a transparent lossy encoding presumably would also preserve any watermarks.
- dTal 5y ago
  Yes. The entire supposed value proposition of watermarks is to survive re-encoding / the analog hole.

adrianN 5y ago

If the listener doesn't know the "true" information, it is sufficient if the watermarked version sounds plausibly like a real sound. I think it's too strong to require the watermark to be completely inaudible. It is sufficient if given two recordings of unknown sounds a listener can't tell which one is watermarked and which one isn't.

greenthrow 5y ago
As a musician; no. That is not sufficient. Any audible watermark -- and as the grandparent comment correctly points out, that is any that is going to do its job -- is unacceptable. It is modifying what the artist intended you to hear in a destructive way. It is destroying the original performances. This is a terrible practice.
- kyleplum 5y ago
  Are you against all lossy compression methods as well? The watermark can simply be a slight tweak of the compression algorithm that could as well have been done for non-watermarking reasons.
  - cortesoft 5y ago
    I think the point is that the watermark is supposed to survive being re-encoded, so it can’t be something just in the compression algorithm.
    - kyleplum 5y ago
      There is a discussion to be had around watermarks surviving transcoding but I was mostly trying to understand whether the opinion > It is modifying what the artist intended you to hear in a destructive way. It is destroying the original performances. also applies to lossy encoding.
      - dTal 5y ago
        The whole point of lossy compression is that it tries to be inaudible, as a primary concern. The whole point of audio watermarking is that it survives lossy compression. Inaudibility is merely a secondary concern. This is an adversarial relationship, and one that the audio watermarking is doomed to lose. By and large, lossy codecs succeed in transparency, and therefore as an inevitable consequence, watermarking fails at it. After decades of development, lossy codecs are just too good - there's nowhere left to hide information. (It's also worth noting that the consumer benefits from the quality tradeoff that compression makes, in the form of decreased storage and bandwidth. They don't benefit from the audio watermarking at all.)

CharlesW 5y ago

> Audio watermarking is inherently audible, because that is the only way to avoid being stripped out (deliberately or inadvertently) by the incredible technology we have for removing inaudible information from audio recordings: lossy audio codecs. You're assuming that perceptual audio coders do a perfect job at encoding what can be heard* and not encoding what can't be heard*. This isn't true in both directions — they encode detail that can't be heard* in the source, and lose detail that can be heard in the source*. *This is contextual, depending heavily on the listener and the listening conditions.

dTal 5y ago
Not a perfect job. But a state of the art job! The relationship between watermarkers and lossy perceptual codecs is fundamentally adversarial - one side trying to eliminate all inaudible information, the other trying to sneak inaudible information past it. And so much more research has been poured into lossy compression, that the watermarkers just can't win. Bear in mind also that the watermark needs to work with all lossy codecs, so the information must be considered salient by all of them. There's just no way to do this inaudibly.
- karmakaze 5y ago
  I doubt that this is where we are at today. We have higher fidelity transmission compared to a joint-stereo 128kbps mp3, which was probably already enough to carry imperceptible watermarks.

akira2501 5y ago

All major market FM broadcasts in the United States have audio watermarking applied to them, and most likely to their online only streams as well. Do you hear the watermarking in that audio? The system is called CBET and it's based on the psychoacoustic model as well, except it determines the level at which watermark should be injected at. High enough that it passes codecs easily, but just below perception so you generally can't detect the tones that it has added to the audio. The trade is that CBET only moves about 8 bits/second of information through the side channel, which is just enough to push a station ID and timestamp through the channel for Nielsen's ratings purposes.

dTal 5y ago
FM radio is a dumpster fire anyway, quality-wise. Apart from the awful dynamic range and noise floor, god knows how many plugins and mp3 re-encodes are used in the average pipeline. So I wouldn't be especially surprised to find that 8 bits/second extra crap on the pile goes unnoticed. However I'm awfully curious about this system, especially "high enough that it passes codecs easily". I would naively expect that to be highly dependent on the codec and bitrate chosen, and further expect the range between "inaudible" and "codec-passing" to be negative for many common untransparent lossy profiles, like 128kbps mp3. Where can I read more?
- akira2501 5y ago
  It's hard to find information on. The company used to be called "Arbitron" and they filed several patents on the technology, which is where I did most of my research. There are 10 bands, each of which can carry 1 of 18 tones. 16 tones are to signal, so the stream is 4 bits wide, and the other two tones are used as a "STOP" and "SYNC" marker in the data stream. All bands carry identical information, but each bit within a band is encoded with a different tone than any other band. So, it appears random or uncorrelated at first glance, but you can see the pattern pretty quickly if you do a long enough analysis. The same message gets identically repeated 12 to 13 times per minute and the message only changes once per minute. Here's an example isolation of the signal [1]. The coder monitors incoming audio and does a psychoacoustic pass to determine which level the tones should be injected at. If it can't find a good level for a tone, it uses the lowest possible level... which usually works out fine due to the 10 redundant signals in the watermark. Encoders like MP3 see the injected tones as signal and will make the bits available to ensure they're encoded rather than correctly masking them out as non-audible material. The 10 bands help here as well, as even if the encoder fails to code the signal in one band, there's usually enough redundant bands that you can successfully decode the watermark. [1]: https://www.sigidwiki.com/wiki/CBET https://www.sigidwiki.com/wiki/CBET

kurthr 5y ago

I disagree. It depends how many bits you want to encode in what period of time. If you only need 1 bit per second, then it can still be inaudible and not susceptible to _current_ lossy psychoacoustic compression models. Universal was both dumb and greedy (and hopeful?) so they got caught making their music into crap. However, encoding a series of highly discernable tones into the audio is just dumb. Instead they should use phase modulation at low frequencies. Current compression models don't play with subtle changes of meter much, because they mostly use local encoding and there's not much room for improved compression with (non-audible) modulation. Of course, if Universal wanted to be able to accurately detect 5 second clips (rather than 2 minute songs) this would be a lot more difficult... and of course they want every thing, at the expense of listener experience.

karmakaze 5y ago

There's a large gap between audible and detectable. A transmitter could transmit a weak signal in a specific pattern on a number of arbitrary preselected frequencies. They would more-or-less seem like noise lost in the noise floor. Only when you specifically filter for the specific set of frequencies can you discern the pattern that was put there that could not appear by chance. You don't even need to use the same frequencies throughout the transmission. As long as the schedule is decided up-front it can serve like a one-time pad for encryption.

LeoPanthera 5y ago

I am far from an expert in this, but, couldn't you design a watermark that removes certain frequencies in known locations in the spectrum, at known times? Those gaps would obviously stay missing in a compressed version - lossy codecs don't add noise.

montag 5y ago

I didn't say _perceptual_ watermarking, which, as you point out, is at odds with perceptual audio compression... :)