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Encoding data into dubstep drops

blog.benjojo.co.uk

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Re: Encoding data into dubstep drops

#31

Post by mistercow »

vardump wrote: post #30
mistercow wrote: post #26

Earlier quoted context omitted.

What do you mean by "nuke the phase information"?

Probably just that mp3 compression loses phase information? As it indeed does.

Can you elaborate? What specifically about mp3 compression causes the phase information to be lost? Clearly, if you simply take IDCT(DCT(s)) for some signal s, you don't lose phase information, because the DCT is invertible. So are you saying that quantization causes the phase information to be lost? If so, why do binaural recordings still work fine when compressed as mp3s, given that they depend heavily on phase differences between the sounds reaching each ear?

Re: Encoding data into dubstep drops

#32

Post by vardump »

mistercow wrote: post #31
vardump wrote: post #30

Earlier quoted context omitted.

Probably just that mp3 compression loses phase information? As it indeed does.

Can you elaborate? What specifically about mp3 compression causes the phase information to be lost? Clearly, if you simply take IDCT(DCT(s)) for some signal s, you don't lose phase information, because the DCT is invertible. So are you saying that quantization causes the phase information to be lost? If so, why do binaural recordings still work fine when compressed as mp3s, given that they depend heavily on phase dif…

> If so, why do binaural recordings still work fine when compressed as mp3s, given that they depend heavily on phase differences between the sounds reaching each ear?

That's a very good point. If phase information is lost, low frequency stereo sound localization should indeed suffer.

Also discrete cosine transformation indeed keeps phase.

I guess mp3 shouldn't be losing phase information after all.

Re: Encoding data into dubstep drops

#33

Post by asherkin »

gsich wrote: post #24
plussed_reader wrote: post #23

Great article about encoding; this is similar to the DRM the PS3 uses on video content. It's a low bit rate signal, but after enough time of the movie playing enough bits are generated to trigger the DRM flag and stop playback.

Cinavia is similar: https://en.wikipedia.org/wiki/Cinavia Can't find stuff about Digital Restriction Management for the PS3, you sure there was something inside the video stream?

Pretty sure they're talking about Cinavia, as the PS3 was one of the most well-known implementors of it.

Re: Encoding data into dubstep drops

#34

Post by gsich »

asherkin wrote: post #33
gsich wrote: post #24

Earlier quoted context omitted.

Cinavia is similar: https://en.wikipedia.org/wiki/Cinavia Can't find stuff about Digital Restriction Management for the PS3, you sure there was something inside the video stream?

Pretty sure they're talking about Cinavia, as the PS3 was one of the most well-known implementors of it.

Yes, but that's in the audio signal.

Re: Encoding data into dubstep drops

#35

Post by phobius »

jbeckham wrote: post #17

I'm pretty sure that this would drop the volume of the 0-100hz range to half the volume since we dropped the amplitude to 1/2 and shifted. Any sound system with loud subwoofers would be able to detect the difference, but woofer only systems would probably leave the modification mostly undetectable.

spot on. also there's likely to be some phase issues in some mixes

aside: seems to be a smooth enough lerp between bits so as not to destroy speakers, but might cause a record needle to jump (can anyone more versed weigh in here?)

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