sergeauckland
pfm Member
I suppose you are right about that with standard dithering and perhaps a fixed amount of scaling, but when the process incorporates a delta-sigma modulation element I'm not sure you can rely on being able to represent the higher waveform peaks in the 32-bit data without also scaling the 16-bit data down. Does that make any sense!?
Bare in mind we are talking about the inner workings of a DAC chip, not a mastering processor or something with significant processing power or allowance for latency. My understanding of how exactly that works is not good enough to really continue this line of conversation. You talk about processing at 32-bit and then dithering back to 16-bit but given the actual DAC inside the chip tends to be no more than 6-bit run with oversampling and modulation, is this actually what happens? Confuses me!
Not sure! Like you, I struggle to get my head round these things.
Any process on a, say, 16 bit signal, even something as simple as reducing the gain by 3dB creates a signal of more than 16 bits. This is because the numbers representing the signal are multiplied by the gain factor and so 16 bit data ends up as a 32 bit data. This data is then dithered down to 16 (or 24) bit before it's passed to the DAC for converting to analogue. I don't know what happens to delta-sigma data, but as bit depth is converted to oversampling, presumably the sample rate doubles, as the bit depth can't change as it's already 1 bit. Mathematically, it seems to me to be the equivalent.
That all this can be done with minimal latency in digital mixers or Sample-rate-converters leads me to think that the maths is understood and the silicon well implemented. Whilst it might be acceptable in Hifi where what it sounds like seems more important than getting the maths right, it isn't acceptable to major broadcasters and recording studios where conformity with standards and accuracy is required.
The digital mixers and routers that the BBC and major commercial networks purchased were all deemed fully acceptable, so I expect that they got the maths right. I wish I could get my head round it better!
S.