If a signal is imperceptible to human ears but detectable by a program, it's a prime candidate for being thrown away by lossy compression to save space. All the

If a signal is imperceptible to human ears but detectable by a program, it's a prime candidate for being thrown away by lossy compression to save space. All the low hanging fruit there has long since been grabbed. The whole point of an audio watermark is that it must survive re-encoding, but it's a race that cannot be won.