[HN Gopher] Encoding Data in Dubstep Drops
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Encoding Data in Dubstep Drops
Author : albertzeyer
Score : 123 points
Date : 2021-01-15 13:12 UTC (9 hours ago)
(HTM) web link (blog.benjojo.co.uk)
(TXT) w3m dump (blog.benjojo.co.uk)
| iamacyborg wrote:
| Whatever that music is, it sure ain't dubstep.
|
| I wonder how well it'd work with something like this
| https://www.youtube.com/watch?v=VEAf_ZztCP0
| have_faith wrote:
| I know the point of the article has nothing to do with the
| definition of dubstep so it took a lot of restraint to not
| write something about it ha, difficult when you grew up
| listening to the early stuff.
|
| I'll take this as my only chance I'll probably get to post
| dubstep on HN in a valid discussion:
|
| https://www.youtube.com/watch?v=rc85cGTlKLY
|
| https://www.youtube.com/watch?v=dwva123XBMk
|
| https://www.youtube.com/watch?v=l2n7w1H0pRQ
| 1MachineElf wrote:
| Skrillex is actually regarded as a leader in Brostep, a
| subgenre and/or style of Dubstep. At least in the USA, Brostep
| has practically supplanted Dubstep and co-opted the name. This
| has been occuring for about the past 10 years. A big factor is
| the "drop" part of Brostep sounding very attractive to non-EDM
| people who head-bang, and to whom traditional Dubstep would be
| percieved as "boring" or not stimulating enough (without
| intoxication). This has led to a re-enforcing cycle where
| domestic EDM festivals reach greater audiences, and so they
| keep promoting Brostep as Dubstep.
|
| Personally, I'm not a fan of this shift. I prefer EDM from the
| era of the track you linked to, and/or contemporary artists who
| emulate the older styles.
| iamacyborg wrote:
| Oh I know, I just get irrationaly annoyed by people calling
| this stuff dubstep. It feels like half the problem is people
| and/or clubs don't have soundsystems appropriate for playing
| bass-heavy music at the right level, so they end up listening
| to stuff that's light on the low-end but still calling it
| "dubstep".
| blovescoffee wrote:
| Pretty much every genre changes significantly over its
| lifetime though. It seems like you could just say you like
| early dubstep just like people say, "I like old school hip
| hop" all the time.
| iamacyborg wrote:
| I get what you're saying but the sound is so completely
| different it's not a simple evolution of style.
|
| Listen to dnb from two decades ago you can still see
| where current stuff comes from. Compare early Digital
| Mystikz stuff with Skrillex and you wouldn't call them
| the same thing.
| 1MachineElf wrote:
| You are probably right. For EDM, cultural differences have
| kept the US lagging behind Europe and the UK. EDM-specific
| clubs are not common outside of major cities known for
| nightlife. A lot of EDM tours end up at venues that aren't
| designed for EDM. These are the conditions informing
| people's tastes, so probably a big factor for why bass
| isn't as prominent as elsewhere. There truly are fans an
| places where it is very much alive, just not as strong as
| other places IMO.
| tomc1985 wrote:
| The bass music underground is alive and well in many
| parts of the US.
|
| Mainstream it is not, and THANK GOD for that
| the_local_host wrote:
| Brostep may be Dubstep Disneyland, but I'm not sure if
| being unconcerned with filing music in the right
| subcategory counts as "lagging".
| rorykoehler wrote:
| This still gets played on a weekly basis in our house
| https://youtu.be/qwCr9QRNMc4
|
| To save a click... It's the garage track largely credited as
| the birth of dubstep
| jk7tarYZAQNpTQa wrote:
| "Zed Bias - Neighbourhood" is actually regarded as one of
| the first dubstep songs, or at least a transition one.
|
| Here are some other "true" dubstep tracks, in no particular
| order:
|
| - Burial - Archangel
| https://www.youtube.com/watch?v=3J1gvgwHblI
|
| - Rusko - Jahova
| https://www.youtube.com/watch?v=1OE_jjJkkD8
|
| - Coleco - Taostic
| https://www.youtube.com/watch?v=krGadL6Je6A
|
| - Kode9 - 9 Samurai
| https://www.youtube.com/watch?v=1-rEAe4C8gk
|
| - Skream - Mignight Request Line
| https://www.youtube.com/watch?v=vJGXRQ9vBoU
| zebraflask wrote:
| I'd make a case for El-B, too:
|
| Express: https://youtu.be/SLbXmPvtZXA
|
| A lot of proto-wobble in this one.
| iamacyborg wrote:
| I'd say Rusko is responsible for the whole brostep thing.
| You can see how it all grew from his tunes.
| monocasa wrote:
| Yeah, Woo Boost was a divergence point for the genre for
| sure.
| oarabbus_ wrote:
| It's still very garage/2steppy. I think Anti War Dub by
| Digital Mystikz is generally considered the birth of
| dubstep. Of course, ask 10 people and you'll get 10
| answers.
| iamacyborg wrote:
| Midnight Request Line is the one I hear most frequently.
| henearkr wrote:
| Same, I did not know Skrillex but I dislike this style.
|
| On the other hand I love Fonik, for example.
|
| I love even more Deadmau5, E.T.H, ...
| tomc1985 wrote:
| Skrillex ruined dubstep in the 'states. And he looks like a
| total d-bag.
|
| I hate that guy.
| ljm wrote:
| Listening to the Skrillex samples in the article, it just
| sounds like DnB but... obnoxious.
|
| The Loefah track in the parent comment though, I can get
| behind that.
| iamacyborg wrote:
| It's even more obnoxious than breakcore, which is saying a
| lot.
| djxfade wrote:
| Yeah, this is the American "Dubstep" commonly referred to as
| "Brostep". Damn I miss the real Dubstep sound!
| oarabbus_ wrote:
| This fell out of style for the most part in America 5+ years
| ago, FYI.
| _underfl0w_ wrote:
| Can confirm this is no longer the new thing, but FWIW, jazz
| music similarly fell out of style ages ago, but that
| doesn't make new stuff in the genre uninteresting to those
| who enjoy it irrespective of hype value.
|
| That is, it's no longer nifty and fashionable to listen to
| this type of "Brostep", but people who liked it without
| regard to its social status may continue listening to new
| material as though nothing changed, while others may have
| grown tired of the sound or the social clout it may have
| brought them to be "in the know" or part of some zeitgeist
| and simply kept up with "today's hits".
|
| The same is true of lots of genres IMHO.
| iamacyborg wrote:
| Still some bangers being released on Sentry records, Deep
| Medi, Bandulu and a bunch of other labels.
| sneak wrote:
| I was hoping that this would be encoding the data in the audible,
| data-sounding part of the sound.
|
| The technique described could be used on any bass-heavy music,
| and is in no way related to dubstep or its data-sounding-ness.
| marcan_42 wrote:
| The way the author went about doing and explaining this is
| somewhat confusing. What he arrived through that strange band
| split/merge process is actually ~identical* to:
|
| - Apply an EQ filter that lowers the volume of the 0-100Hz band
| by 6dB (this happened because he halved the amplitude of the
| 100Hz band)
|
| - Add a slow binary digital signal at around ~4 baud (2Hz
| fundamental), with slopes smoothed to around 10% of the bit time.
|
| This has nothing to do with dubstep or bass drops - it would work
| for any song. It's just modulating data in infrasound, at 2Hz,
| which is well below the threshold of human hearing. The problem
| here is that he's also needlessly reducing the level of the
| 0-100Hz band to half the amplitude (6dB), which completely kills
| the bass feel of the original song. Dubstep fans will not approve
| (and he needs better speakers if he can't hear the difference).
|
| A much simpler, more sensible process would be to just do this:
|
| - Apply a steep highpass filter at 20Hz (the limit of human
| hearing), to remove any inaudible low-frequency (infra)sounds.
|
| - Reduce the volume of the overall song by, say, around 1dB, to
| make a bit of headroom for the modulated digital signal
|
| - Encode whatever you want in those 20Hz in the headroom you
| created (the amplitude can be quite low, e.g. 5%, it doesn't need
| to move the whole waveform over).
|
| Then to decode it just lowpass the signal at 20Hz and do your bit
| detection after that - the filter will remove the audio, leaving
| only your signal, so it doesn't matter that your signal isn't a
| whole 50% of the output power. Now the song is only 1dB quieter.
| You can use as simple or as fancy a modulation technique as you
| want in that 20Hz band. You could use (normal) ASK as he did,
| just lowpass it to remove any high frequency components. You
| could use FSK. You could use QAM. Whatever.
|
| * His process actually also messes up the original 100Hz band by
| modulating it with a ~4Hz square waveform due to the way he does
| the modulation by inverting and interpolating, which is going to
| create harmonics and other ickiness around the transitions, as
| well as does not guarantee the absence of clipping due to the way
| he only reduced the amplitude of the low 100Hz band (this process
| can actually _increase_ peak levels, as can happen any time you
| use frequency filtering - try his high-pass filter command on
| this file and watch sox complain of clipping, even though the
| original file does not clip:
| https://mrcn.st/t/filtering_clips.wav ), so I would not recommend
| trying to emulate his approach precisely even if you want to
| achieve the same actual effect, since it's actually quite a silly
| way of going about doing it :)
| dylan604 wrote:
| Isn't this precisely what some ad tracking people or rights
| management are doing? Aren't they adding audio that is out of
| range for human consumption but things like Alexa can hear them
| so that, or so the broadcaster can tell that a pub is
| broadcasting a match without paying for it, etc?
| blovescoffee wrote:
| Do you have a link? I assumed a low pass filter was applied
| to the signal to reduce unnecessary data transmission. I have
| heard about what you're saying and I'm not dismissing it. One
| could run their television through a low pass filter to get
| around such tracking, right?
| dylan604 wrote:
| That's kind of what I was implying with one of my other
| replies. This filtering is something that Alexa/Googs
| should be doing on thier end. Their mics should only be
| listening in the frequency ranges of what human voices
| exist.
| marcan_42 wrote:
| This kind of modulating data in infrasound or ultrasound is
| common, yes. It has been used in toys too, e.g. things that
| respond to certain sounds from a show. chibi-tech stuck some
| reverse engineered ultrasound triggers for a certain line of
| toys in some of her songs :)
|
| https://twitter.com/chibitech/status/1237326756672983040
|
| Infrasound only works digitally because no speaker system can
| reproduce frequencies that low, and many analog systems will
| corrupt them (e.g. AC coupling). Ultrasound is therefore used
| most of the time in practice, but I believe infrasound has
| been used in digital song watermarking for DRM/copyright
| tracking purposes.
| GuB-42 wrote:
| Not really, unless you are doing a 1:1 digital copy,
| frequencies outside the range of human hearing are often
| removed.
|
| Frequencies outside the range of a speaker are often filtered
| out as it can create distortion or even damage. And the job
| of lossy compression is to remove everything that you can't
| hear in order to save bytes, and limiting the bandwidth to
| what you can hear is the most basic step.
|
| Instead, DRM systems typically encode data over a wide range
| of frequencies (spread spectrum), well within the audible
| range. It is designed in such a way that you could hear it in
| theory, but don't notice it because it blends with background
| noise. It is very robust, resisting compression, recording
| and even deliberate attacks. In fact, it is one of the
| techniques used by the military radios to resist jamming.
| _underfl0w_ wrote:
| You can also trigger wake words like "Ok Google" or "Alexa"
| by using _harmonics_ of normal human voices that are outside
| the range of audible sound. The key is that the mic can't
| differentiate between the harmonics and actual speech of
| normal human pitch and so the trigger is set off, but the
| sound isn't audible to humans.
|
| I don't have a link to the paper handy (sorry!) but IIRC I
| found a white paper on ArXiv called "Dolphin Attack" or
| similar that demonstrated this. It was a fun read.
| dylan604 wrote:
| While technically that sounds like a cool hack, it sounds
| like a dumb thing to actually allow to happen. "Okay
| Google" or "Hey Alexa" outside of the frequencies
| reproducible by human voices should be filtered out
| completely. At least, from my comfy chair nit picking
| someone else's work. Of course, by not filtering the
| acceptable bands allows them to do all of the ad
| tracking/rights management things they are allowing to
| occur. The fact that Alexa/Google is able to do these ad
| tracking/rights management is just another example showing
| that the mic is listening 100% of the time.
| IIAOPSW wrote:
| The limit of human hearing is a bit above around 20KhZ.
| Emphasis on the K. It is totally possible to hear 20Hz noise.
| In fact 20KhZ is better for this because you can use a higher
| bit rate and that band is going to have very little intentional
| noise to begin with.
| marcan_42 wrote:
| Wrong side of the spectrum. The lower limit of human hearing
| is 20Hz. It is not possible to hear <20Hz noise. It is,
| however, possible to _feel_ it, if the sound pressure is loud
| enough and you actually have a subwoofer capable of
| reproducing those frequencies, but that is rather unlikely
| unless your subwoofer is a cut-out in your room 's wall with
| a fan in it.
|
| https://en.wikipedia.org/wiki/Rotary_woofer
|
| If you feed a 20Hz signal to a typical home subwoofer (or
| even most club systems) and hear something, you aren't
| hearing 20Hz. You are hearing a bunch of high frequency
| rubbing noises as the speaker cone moves at 20Hz, trying and
| utterly failing to couple any amount of energy at that
| frequency into the air. This is why many songs these days are
| produced with "bass maximizers" and why modern laptops can
| sometimes have "decent bass". It's not bass, it's a filter
| that purposely distorts the bass, which your speakers can't
| reproduce, into higher frequencies, which it can and which
| we've learned to associate with heavy bass played through
| systems that can't reproduce it but distort instead.
|
| Just for reference, I believe these are the subs we use at
| Euskal Encounter. I can vouch for the fact that they can make
| the floor shake in a massive event hall venue. Low end
| response: down to 28Hz. No more.
|
| https://jblpro.com/en/products/vtx-b18
|
| It is indeed better to modulate data in ultrasound since you
| have a lot more bandwidth - except for the fact that any
| lossy compression applied to your file is going to completely
| destroy your data. This is one thing the author got
| absolutely right.
| corytheboyd wrote:
| Big shout out to the ideas like this that are just someone having
| fun and being excited enough about the outcome to share with the
| world :)
| have_faith wrote:
| a "Big shout out" is very appropriate for a post about dubstep
| petercooper wrote:
| Ben's blog is full of this stuff, it's fantastic, definitely my
| favorite 'doing fun stuff with tech' blogger of recent years.
|
| https://blog.benjojo.co.uk/post/dns-filesystem-true-cloud-st...
| is one of my favorites.
| adamddev1 wrote:
| This is really cool. Can the author or anybody else tell me how
| he made those gif sketches with the moving waveforms and
| equations?
| arilotter wrote:
| A DC offset, which amplitude-shift keying like this introduces,
| isn't so nice to your speakers. It might cause them to heat up as
| the offset waveform holds the magnet out in one direction. I do
| love the idea of hiding data in "messy" audio, though :)
| arcticbull wrote:
| Aren't all speakers AC coupled? Should be filtered out by
| somthing as simple as a blocking capacitor no?
| arilotter wrote:
| Yes, it's unlikely to cause problems in any real-world setup,
| but it's theoretically possible :P I've edited my original
| comment to clarify that it won't always be the case.
| lostlogin wrote:
| Signal that can damage hardware is something that used to
| be discussed with CRT monitors back in those ancient times,
| and rumours existed of a virus that played on this.
|
| Having damaging audio signal is a new one for me.
| Unklejoe wrote:
| Not necessarily. The amplifiers sometimes are though.
|
| In a normal 2 or 3 way speaker cabinet, you'll have an analog
| crossover which consists of something like a capacitor in
| series with the tweeter (high pass filter), and an inductor
| in series with the woofer (low pass filter).
|
| In that case, the tweeter is protected from DC, but the
| woofer isn't.
| arcticbull wrote:
| Very cool thank you!
| isoprophlex wrote:
| Also, if the data rate is low enough, compression will probably
| also remove such dc components?
| tekstar wrote:
| If it's audio rate how is it different than a squarewave?
|
| Edit: looked closer at the post, the DC offset lasts for over
| 100ms per cycle.. yeah that's a problem
| virgil_disgr4ce wrote:
| The problem is not the waveform, it's the DC offset requiring
| more constant current to the voice coil.
| mkr-hn wrote:
| All waves are made of sine waves. DC offset is when the
| signal is too much one way or another.
| dylan604 wrote:
| Maybe in analog, but in digital, they are squares and what
| not type of waves.
| layoutIfNeeded wrote:
| Sigh... No, digital signals are not "square waves".
| https://youtu.be/cIQ9IXSUzuM
| bhj wrote:
| I always laugh when vinyl is described as more "pure".
| There's nothing more pure than math, and that's digital
| PCM audio. Sure, it's stored as discreet samples, but
| that's not how it comes out of speakers. The
| digital->analog converter will give you 1:1 perfect
| representation of the original waveform as long as you
| sample at 2x the highest frequency desired and there's a
| low-pass filter in place.
| anamexis wrote:
| For the record, I don't think vinyl enthusiasts ever
| describe vinyl audio as more pure. "Pure analog," yes,
| but that's different (and true). It's generally
| acknowledged by vinyl enthusiasts and audiophiles that
| vinyl introduces a lot of imperfections, which some
| people prefer.
|
| Also worth noting that an _ideal_ D /A converter will
| give you the exact waveform back, but such a device does
| not exist (but you can get pretty close).
| dylan604 wrote:
| Have you ever played with an Arduino or similar device?
| Comparing inputs signals on a digital pin vs an analog
| pin? Hopefully, you'll agree it's the same concept. If
| you haven't, I'd encourage you to try one out. They are
| loads of fun. I am a huge fan of analog, yet digital is
| just so damn convenient. If you have played with one,
| you'll understand why your comment makes me smile and
| chuckle.
| grkvlt wrote:
| Not strictly true, you must sample at 2x the frequency
| _and_ at sufficient resolution in the amplitude domain,
| i.e. an ADC that samples at 44 kHz but with only one bit
| of resolution (outputs a 1 for positive input voltage and
| 0 for negative, say) would be pretty awful...
| dylan604 wrote:
| Sigh... you are wanting to show me that we can do A/D and
| D/A again? Thanks, I was totally unawares that we could
| do that. I've never heard an audio signal played back
| once it was digitized. My life is now complete.
|
| What this guy is showing is not a digital signal. It is
| an analog signal that has been generated from digital
| data. Not sure what the point of all of this was, but
| thanks, I needed a break from finding this bug I've been
| trying to squash.
| _underfl0w_ wrote:
| Your comment might be more helpful (i.e. more likely to
| be read by others who could use the information you're
| providing) without the snark.
| magicalhippo wrote:
| In a traditional amplifier the DC should be blocked by the DC
| blocking capacitors, but I guess with modern full-bridge
| class-D amplifiers which don't require those it'll have to be
| done on the software/digital side?
| dimnsionofsound wrote:
| I was thinking it'd be something more like this:
| http://www.windytan.com/2015/10/pea-whistle-steganography.ht...
| TheActualWalko wrote:
| Hey cool! Here's essentially the same encoder in a few lines of
| JS, you can run this on https://wavtool.com by pressing cmd+;
| (() => { const message = 'asdf'; const
| messageBinary = message.split('').map(c =>
| c.charCodeAt(0).toString(2)).join('').split('').map(Number);
| const bitDurationSeconds = 0.1; const shiftSize = 0.1;
| return wavtool.mapSamplesCommand((sample, index, channelData,
| settings, context) => { const bitIndex =
| Math.floor(index / (bitDurationSeconds * context.sampleRate));
| const shift = bitIndex < messageBinary.length ? (2 *
| (messageBinary[bitIndex] - 0.5)) // [0,1] => [-1,1] :
| 0; return sample + shift * shiftSize; });
| })()
| tekstar wrote:
| Reminds me of Aphex Twin (and some other artists) embedding
| images in the spectrograph render of their songs:
|
| https://www.magneticmag.com/2012/08/the-aphex-face-visualizi...
| 1vuio0pswjnm7 wrote:
| I have read that is quite common in, e.g., file carving, CTF
| challenges.
| tekstar wrote:
| Stenography is common, but usually it's just modifying the
| last bits of an image or hiding the extra payload after the
| image data. This is "drawing" within the audio spectrum,
| making the image out of audio that will be audible.
| BugsJustFindMe wrote:
| Steganography. Stenography is something else. :)
| tekstar wrote:
| This gets me every. Time. Lol
| brianzelip wrote:
| Just going to drop this here then,
| https://www.youtube.com/watch?v=eTNx_SsApu4
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