PCM and PWM in decoding CDs!

Discussion in 'Homework Help' started by thenzman, May 17, 2007.

  1. thenzman

    Thread Starter New Member

    May 17, 2007
    This is a assignment question which begins below:

    Can anyone provide me some links for further research, firstly I don't know what the terms PCM and PCW mean, so would like if someone could provide a link to me which explained them.

    Any other sites to help with my assignment will be appreciated.

  2. Papabravo


    Feb 24, 2006
  3. thenzman

    Thread Starter New Member

    May 17, 2007
    I had already read the wikipedia link and some websites I found on google was not very clear though, so I posted here on the forum for any other sites you could recommend.

    Quoting from wikipedia

    Why was 16 bit chosen? Can't anything higher have been used?

  4. beenthere

    Retired Moderator

    Apr 20, 2004
    Frankly, I'm still trying to make sense of the original question about using PCM or PWM to "decode" CD's. The data thereon is purely digital in nature, so modulation techniques are hardly germaine. The audio is digitized by an A to D converter, and played back by the reverse. Modulation never takes place.

    One can find audio A to D converters of up to 24 bits. That's one part in 16 million/bit, versus 1 in 65,536 for 16 bit audio. It's a bit hard to imagine how anybody could really hear any of those last 8 low-order bits.
  5. thenzman

    Thread Starter New Member

    May 17, 2007
    I am giving up answer the question all I can come up with is that the disadvantage of PCM is that the signal accuracy is reduced because of the quantizing of the samples.

    As for advantages I don't see what PCM has when there are more better ones out there like HDCD, SACD
  6. Gadget

    Distinguished Member

    Jan 10, 2006
    Every bit adds 6dB to the dynamic range...(also closely related to the max S/N ratio). 16 bits give a theoretical dynamic range of 96 dB and the sample rate of 44.1kHz gives a theoretical frequency response of just under half that 44.1.
    When CD's were developed that was well above anything previously available, and pretty much at the limits of the then technology. Today we are capable of much more.... but apart from studio use, why bother when no one can hear the difference.