Roon, Airplay, iPhone and HomePod issues

[Martin_Webster]

@Richard_Bradshaw

But the AAC is not 24 bit, it has been taken and converted from a CD rip, which is obviously 16bit.

AAC is lossy and has a nominal bit depth determined by the decoder. Either way, a lossy format and classed as low quality. Hopefully, this post will help your understanding.

ACC MP3 lossy output 24bit

Once audio has undergone lossy encoding, it no longer has an inherent bit depth. The encoded bits can be thought of as a mathematical description of how to reconstruct an approximation of the waveform that went into the encoder. The decoder usually calculates the reconstruction using floating point or integer math with at least 24 bits of precision. We chose to output 24-bit PCM in order to avoid introducing unnecessary dither to the decoded audio. Dither is basically a necessity when dropping a…

Anything lossless over 44.1kHz 16bit is converted to meet the Airplay 1 limitation. Regardless, as explained before, and specifically in the post linked by @RBM, Roon considers Airplay high-quality since it is not possible to confirm that Airplay devices are indeed bit-perfect.