03-Dec-2019, 20:53
(03-Dec-2019, 19:06)seb Wrote: Interesting question regarding the re-encoding. My guess is though there won’t be any noticeable difference when streamed over AirPlay which delivers basically CD quality for audio. So the downsampling should be limited by the 16/44.1KHz quality. I have not tested it though. I am also not sure where the rumor comes from that AirPlay 2 delivers higher quality audio. I was also interested in this question, but the info I gathered was that there was no change in the Bitdepth/Sample rate specifications. As AirPlay 2 is already implemented with other manufacturers I guess we would have heard about a performance increase. Regarding ALAC transport protocol there should also be no difference to FLAC as it is just a container. So my bottomline would be to limit Streamingservices to 16/44.1 when using AirPlay as there should be no alterations and it would consume less bandwidth.
This is what I figured out so far. I am no engineer however, so if I quoted something wrong or needs further explanation please feel free to correct me.
Hi seb, I am by no means an expert on AirPlay (I know a bit more about ALAC as I worked on it a while back) but based on the little I do know I think things are getting a little bit confused here.
AirPlay and ALAC are different things. AirPlay is a family of protocols designed to send (display, stream, mirror) media from an iOS device or iTunes to a compatible output device (audio and/or video renderer). Audio can be streamed via Airplay using a variety of codecs like ALAC, AAC & PCM. ALAC is capable of encoding up to 8 channels of 32/384 audio, so no problem there. The AirPlay protocol defines things like service discovery, stream setup, simple control (start, stop, timing sync, error correction etc.) and advanced control (volume, metadata, album art etc.). AirPlay isn't a codec and doesn't define or constrain the resolution of the audio, it just defines the method by which the stream can announce what it contains and the device can advertise what capabilities it has (formats, resolution, remote volume, display etc.)
So within the scope of what the codecs can support the audio resolution limitations of an AirPlay system are defined by the transmitting device and the receiving/rendering device. The 16/44.1 limitation was not so much a limitation of Airplay 1 per se, but an implementation decision in the iPhones, iPads, AirportExpresses and AppleTVs that supported it. This might have been based on the capabilities of the devices themselves, or an implementation decision by Apple to provide "highest common denominator" compatibility or to mitigate throughput or reliability problems streaming over wireless networks. I have no idea. But whichever it was I am pretty sure it is not a limitation of AirPlay itself.
Very happy to be put straight if anybody here has better info.
