|Originally posted by Cor
A delta-sigma DAC or ADC, although typically just one chip or component, can be viewed as a string of components. The stream of 1-bit samples in between the interpolator and 1-bit DAC in a delta-sigma DAC is basically what DSD is. The only difference is that the sample rate in your typical delta-sigma DAC is much higher than the sample rate of DSD as implemented for SACD's. Still, DSD has a high enough sample rate to get the job done. ...
This is simply going over old ground, and a lot of your post is materially incorrect, however I will take time to address just a few points. Yes PCM is a base storage medium. However, your arguments amount to saying that a train and a car are materially equivalent because they both run on wheels. When folks state what you say, I always ask the rhetorical question, Does Sigma Delta modulation (from now on referred to as SDM) only apply to 1-bit words?
SACD's base sampling rate 2.8 MHz is much like having a CD with 44.1 KHz. Once you are inside the DAC, you can oversample to higher sampling frequencies to your heart's content as long as the silicon technology holds. Secondly the fundamental difference between PCM and DSD is that PCM stores an absolute value and DSD stores a relative value. Secondly, PCM trades off word length against sampling frequency, whereas SDM trades off sampling frequency against wordlength and there are advantages and disadvantages to both approaches.
An Interpolator is used to oversample to higher frequencies and longer word lengths. The word you are looking for is a differentiator, and you can differentiate any sigma-delta word to a PCM word. As I mentioned in another thread a while ago, a 1-bit sample is a special (or initial) condition since the LSB and MSB are one and the same and a valid word must be >0. That special condition is what has fundamental significance. However, you can always oversample to a higher frequency and a longer word length and once your sample is greater than 1-bit, the special condition ceases to hold.
Lastly your remarks that
|Currently, DVD-A's can hold more audio data of a given quality than SACD's can.
is factually incorrect, if that were the case why are MCH DVDAs stuck at 96/24 and stereo DVDAs can achieve 192/24
|DVD-A's are also considerably more flexible to author.
This has not been borne out in the field, in fact one of the comments made by one of the mastering houses is that because SACD is an audio only format it is easier
to master than the hybrid AV format that is DVDA. Looking at the considerable inconsistency in operating existing DVDAs I do not think he is far away from the truth. I am sure here what you trying to say is that PCM is easier to DSP, however that will be the case with most old technologies vis a vis their newer competitors.