On 11/05/2011 13:21, Le_Forgeron wrote:
> Le 11/05/2011 10:36, Invisible a écrit :
>>
>> I would suggest, however, that 4 bits/sample would be inadequate for
>> audio applications.
>
> For a linear PCM, yes.

Linear PCM is the standard way to describe digital sound signals.

I should think that even logarithmic PCM would sound poor at 4 bits/sample.

> But one of the latest format (SACD) use only 1 bit/sample (at a silly
> high sampling rate) in a non-PCM storage.

You mean pulse density modulation.

> (in fact the bit is simply a up/down delta, and it make easy to get ride
> of the digital to analogue converter in the mass production of player:
> use the bit to drive digitally a transistor, accumulate output in a
> capacitor, the connection to the ear-set is done directly on the
> capacitor (volume is set by resistor on the transistor's upstream))
> 2 cheap components (or even less if you can fake the capacitor with
> circuitry) to replace an expensive DAC.

I'm not sure whether this is true.

I was also unable to discover what encoding SACD uses for its data. I 
rather doubt that raw PDM written directly to the disc surface, any more 
than a normal CD contains raw PCM.

> Delta Sigma encoding is really painful to convert back accurately in PCM.

Actually it's trivial. You just need a digital low-pass filter.

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