It looks like DVD-A can sample up to 192.
DVD-Audio, like the compact disc before it, is based on Pulse Code Modulation (PCM) digital audio technology. In this process, incoming analog audio is fed to an analog-to-digital converter that essentially measures ("samples") the instantaneous value of the signal and stores the result as a binary number: a "digital word." This is done tens of thousands of times a second – 44,100 samples per second in the case of the compact disc, and up to 96,000 or even 192,000 times per second for DVD-Audio. The more samples per second (the higher the "sample rate"), the better the quality – up to a point. In fact, we can’t really hear any significant difference above about 64,000 samples per second (a "sample rate" of 64 kHz), but the DVD-A sample rates of 88.2 and 96 kHz are simple multiples of the 44.1 and 48 kHz rates used in CD and DVD-Video, which means that converting between them is easier and sounds better. And MLP (Meridian Lossless Packing, the lossless compression system used in DVD-Audio) recovers much of the extra storage space needed by higher sample rates. Even so, it can be argued that sampling at 192 kHz is a complete waste of time.
PCM stores each sample as a digital word a certain number of binary digits ("bits") in length. Up to a point, the number of bits determines the noise floor and dynamic range of the digital system, and in some cases the amount of detail you can capture. The compact disc format uses 16-bit words to give a noise floor at about –96 dB. DVD-Video generally uses 20-bit words. And DVD-A can use up to 24-bit words. Above about 22-24 bits, there is no point in adding bits, as the noise floor of the system is below the threshold of thermal noise and other effects. A true 24-bit converter, for example, would give a noise floor of –144 dB, and apart from the fact that you can’t realistically do anything with a –144 dB noise floor, no one can make components that quiet anyway: most 24-bit converters are hard pressed to reach –120dB. So 24 bits is more than enough.
This all means that the general sample rate and word length used in DVD-Audio surround recordings today – 24 bits, 96 kHz sampling – is just about right for high quality PCM.