I wonder how said watermarks will survive lossy audio compression since a big part of lossy audio compression is to remove parts of the signal humans can't hear and won't notice is gone.
> Cinavia's in-band signaling introduces intentional spread spectrum phase distortion in the frequency domain of each individual audio channel separately, giving a per-channel digital signal that can yield up to around 0.2 bits per second.
> Cinavia is designed to stay within the audio signal and to survive all common forms of audio transfer, including lossy data compression using discrete cosine transform, MP3, DTS, or Ogg Vorbis. It is designed to survive digital and analog sound recording and reproduction via microphones, direct audio connections and broadcasting, and does so by using audio frequencies within the hearing range.
*#>Synth manufacturers start licking their lips.
And, for the amateur muso's that still don't get it: imagine having to pay/ have had paid for every time a dx7 was used in a tune, or an ms20?
But it's not audible in the sense that human ears can't discern it.
If an audio signal survives a lossy compression algorithm, then there are two possibilities:
- the compression algorithm should be improved, as it preserves some data that isn't important to the human ear
- the signal is audible
It's information theory. Either you can encode additional information without impacting the result, in which case the compression algorithm could use it to be more efficient, or you can't. TANSTAAFL.
There is an obvious third choice: the gain in compression isn't worth the effort of writing code to detect these non-discernible artifacts.
People are throwing around 0.2 bits/second in this thread. I doubt a company or individual would write code for such a trivial gain, never mind the slowdown in encoding it might cause.
Why wouldn’t it be worth it? You just have to write the code once and it will affect terabytes of music being compressed from that point forth.
The watermark is applied to the spectrogram. Each "pixel" of the watermark represents a small band of frequency in a small time slice. The watermark presumably does something like increase the volume by 1% in the watermarked "pixels" -- basically imperceptibly adjusting EQ by tiny amounts in tiny places.
That will survive lossy compression just fine -- lossy compression applies a low pass filter and then removes whole spectrogram chunks where the signal is below a threshold.
But a watermark will still be entirely detectable in all the chunks that remain.
If you mean dynamic range compression, that's something done as part of mastering. It has nothing to do with DAC.
I imagine this is also the case for audio watermarks, but I'm not sure what the current state of the art is for watermark removal.
This is primarily because those watermarks damage the image. The information about the content of the image beneath the watermark is missing (replaced with the watermark) and would have to be extrapolated or fabricated to replace it.
If the watermark isn't visible as part of the image then there is no missing piece to have to replace.
If you slightly alter the low frequency signals, they will be preserved. 30.1 Hz -> 30.2 Hz.
Quite certain that’s not true. We drop everything pass 20khz simply because it’s outside the average person’s hearing range.
We drop everything under 20hz too - we also cannot hear below that.