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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
by TerrifiedMouse 3y ago
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.
- vachina 3y agoThere was a time when Blu-ray players had to implement such audio watermark decoder, to detect and stop playback unauthorized Blu-ray copies. > 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.
- TerrifiedMouse 3y agoSo the watermark is audible to listeners.
- rcxdude 3y agono, because it's very small phase modulations. The main tradeoff is you need a relatively long segment of audio to detect it.
- InCityDreams 3y agoI recently bought a new synth...i wonder if it has a signature? *#>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?
- 613style 3y agoIt's audible in the sense that it exists completely in an audio modality. But it's not audible in the sense that human ears can't discern it.
- meindnoch 3y agoThe aim of lossy compression is to discard any data that isn't discernible to the human auditory system. 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
- amatecha 3y agoThat's not exactly the aim of lossy compression. Its aim is to reduce data size while introducing as little discernible effect as realistically possible. That usually means optimizing the algorithm such that most of the loss is indiscernible to us, such as in a darkest regions of an image, or the extremely high frequencies in audio -- both areas we don't perceive with too much granularity. Something like spread-spectrum phase distortion may survive compression just fine but still be indiscernible to us. The two are not mutually exclusive.
- AnthonyMouse 3y agoSuppose you could encode 0.2 bits per second of watermark in a recording without humans being able to discern it. Suppose the compression algorithm did the same thing to encode additional information which is part of the recording, allowing it to achieve higher quality at the same bitrate or the same quality at a lower bitrate. 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.
- wizzwizz4 3y agoAnd complexity theory says we can't reach the information theoretical limits with generic algorithms.
- wubrr 3y agoCouldn't they apply the watermark post-compression? But yeah, eventually people will figure out how the watermark works and be able to remove it.
- TerrifiedMouse 3y agoFrankly, if it can be detected, it can be removed. Makes sense no?
- FartyMcFarter 3y agoThink about watermarks in images. They can be removed, but it isn't easy to do so without making it obvious that the image is damaged / doctored. 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.
- greatpatton 3y agoYou can easily train a model to clean watermark from images.
- AnthonyMouse 3y ago> They can be removed, but it isn't easy to do so without making it obvious that the image is damaged / doctored. 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.
- KineticLensman 3y agoModern content-aware fill can very impressively replace dead areas of an image. E.g. in Photoshop 2024
- 3y ago
- crazygringo 3y agoThey'll survive fine. 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.
- neuralRiot 3y agoHow about signal (analog) dynamic compression? If he WM is embedded in the audio data then I won’t survive DA>compress>AD.
- crazygringo 3y agoCan you clarify? A DAC doesn't perform any compression. What dynamic compression are you referring to? If you mean dynamic range compression, that's something done as part of mastering. It has nothing to do with DAC.
- neuralRiot 3y agoNot the DAC but a DSP can do it. So the chain would be DAC> DSP (compression) > ADC What i trying to say is that the “watermark” would theoretically survive data compression (WAV>MP3, FLAC, AAC) but not dynamic range compression.
- dist-epoch 3y agoCompression tends to discard high-frequency signals since they use the most bits. If you slightly alter the low frequency signals, they will be preserved. 30.1 Hz -> 30.2 Hz.
- TerrifiedMouse 3y ago> Compression tends to discard high-frequency signals since they use the most bits. 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.