13-Aug-2018, 20:51
@ada Just because AIR is based on UDP does not mean it has no hand-shaking or guarantee of delivery, etc. as you stated above. It is quite possible to add these capabilities over UDP. In fact (as I'm sure you know) both TCP and UDP are layered over IP, which has the same inherent lack of reliability as UDP. TCP implements guaranteed delivery by using synchronisation/acknowledgement and retries, but its design is not optimised for real-time data transfer. AIR can equally implement (effectively) guaranteed delivery over UDP by using retries in a different and proprietary way.
My investigation into the AIR protocol suggests that it does have feedback mechanisms that would allow it to deliver a bit-perfect stream to the renderer. These are somewhat similar to TCP but simpler, if I understood them correctly. Its job is probably made much easier because the large buffer in the Devialet amp means that it does not have terribly hard real-time constraints.
If the AIR protocol used "raw" UDP with no overlying mechanism to give any reliable, ordered delivery, then depending on the quality of your network and the other traffic on it, I think you'd hear much worse artefacts than the kind of differences (narrower sound stage, lack of harmonics, ...) you discussed in your original post. Specifically, significant drop-outs, stuttering, and/or obvious distortion.
In short, I'm pretty sure you're barking up the wrong tree here: the difference between AIR and UPnP is not down to one being bit perfect and the other not, and not due to the difference between TCP and UDP.
My investigation into the AIR protocol suggests that it does have feedback mechanisms that would allow it to deliver a bit-perfect stream to the renderer. These are somewhat similar to TCP but simpler, if I understood them correctly. Its job is probably made much easier because the large buffer in the Devialet amp means that it does not have terribly hard real-time constraints.
If the AIR protocol used "raw" UDP with no overlying mechanism to give any reliable, ordered delivery, then depending on the quality of your network and the other traffic on it, I think you'd hear much worse artefacts than the kind of differences (narrower sound stage, lack of harmonics, ...) you discussed in your original post. Specifically, significant drop-outs, stuttering, and/or obvious distortion.
In short, I'm pretty sure you're barking up the wrong tree here: the difference between AIR and UPnP is not down to one being bit perfect and the other not, and not due to the difference between TCP and UDP.
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