Is 44.1kHz fine as a delivery format and we don't need anything more?
Just about the only objection from reasonable people I see is that it's hard to filter content in a DAC with that sample rate...
Now, I only have a very superficial understanding of how a (modern) DAC works. From what I've read so far, the input digital signal gets oversampled, which creates imaging of the signal above nyquist (link). That content should then be low-pass filtered. Ideally the filter would not touch content until 20k (for the human ears to enjoy the "full range"), but remove everything above 22.05.
It's not hard to employ such a filter on a PC; a high quality software SRC can do it easily. But it's harder to do it in a DAC and the main reasons are processing power and latency. Supposedly even the SoX resampler, which is high quality and fast, has around 20ms of latency. That's fine for casual music listening, but not for interactive use (such as making music, for instance).
Does all this sound about right?
My question then is, where are we currently with filters in DACs? Are there DACs that can filter really well at low latency? Let's say... flat to 20k and -50dB at 22.05k, with no more than 1ms latency (latency of the DAC itself, not of the additional components or drivers). Does/would such a DAC use a lot of power?
For example, RME's ADI-2 filters are under 1ms, but looking at some graphs, even the sharpest one is still at -13dB at 22.05k. But according to the graph here, it attenuates really well at 24k (dunno if it's the same sharp filter or not).
Mind you, I don't claim that content at 22kHz and above is audible. So in the end this debate could all just be theoretical. I'm imagining some worst case scenarios, like a (young) person with exceptional hearing or -- more realistically -- signals that could somehow end up affecting the equipment and/or leak down into the audible range. For example in that first link, bennetng mentioned DACs with ASRC, which oversample at non-integer ratios and create aliasing in addition to imaging. But I have no idea if DACs like this are common at all...
Just about the only objection from reasonable people I see is that it's hard to filter content in a DAC with that sample rate...
Now, I only have a very superficial understanding of how a (modern) DAC works. From what I've read so far, the input digital signal gets oversampled, which creates imaging of the signal above nyquist (link). That content should then be low-pass filtered. Ideally the filter would not touch content until 20k (for the human ears to enjoy the "full range"), but remove everything above 22.05.
It's not hard to employ such a filter on a PC; a high quality software SRC can do it easily. But it's harder to do it in a DAC and the main reasons are processing power and latency. Supposedly even the SoX resampler, which is high quality and fast, has around 20ms of latency. That's fine for casual music listening, but not for interactive use (such as making music, for instance).
Does all this sound about right?
My question then is, where are we currently with filters in DACs? Are there DACs that can filter really well at low latency? Let's say... flat to 20k and -50dB at 22.05k, with no more than 1ms latency (latency of the DAC itself, not of the additional components or drivers). Does/would such a DAC use a lot of power?
For example, RME's ADI-2 filters are under 1ms, but looking at some graphs, even the sharpest one is still at -13dB at 22.05k. But according to the graph here, it attenuates really well at 24k (dunno if it's the same sharp filter or not).
Mind you, I don't claim that content at 22kHz and above is audible. So in the end this debate could all just be theoretical. I'm imagining some worst case scenarios, like a (young) person with exceptional hearing or -- more realistically -- signals that could somehow end up affecting the equipment and/or leak down into the audible range. For example in that first link, bennetng mentioned DACs with ASRC, which oversample at non-integer ratios and create aliasing in addition to imaging. But I have no idea if DACs like this are common at all...