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Questions about DAC

Old 09-04-02, 04:24 AM
  #1  
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Questions about DAC

I'd appreciate any help from anyone knowledgable about this subject.

What I know:

When a DVD gets encoded it goes thru an Analog-to-Digital process (ADC). There are 2 factors, namely data precision and data sampling. So when a DVD gets encoded as 16-bit/64kHz it means that the data precision was 16 bits (65536) and the data sampling was 64kHz (65536 samples per second).

What I'd like to know:

When DVD players are sold, sometimes the DAC numbers are advertised. For example, the SonyDVPNS315 states that it has 24-bit/192kHz Audio DAC and 10-bit/27MHz Video DAC.

My questions:
(1) Do these numbers represent the maximum bit rate it can decode? Since the ADC already determined the bit rate during conversion, am I correct to assume this? Similarly, say if a DVD is encoded via 120-bit/24MHz (for the sake of argument), then does that mean that the Sony DVD player above will be unable to read this DVD?
(2) Do all DVD players (the newer ones anyway) have an option to display the bit rate of the DVD being played?
(3) How is the data sampling done for Video conversion? I know that for Audio it assigns a numeric value for the current sound wave for each data sample. For video, is it per pixel?
(4) Why does Video DAC require less data precision than Audio DAC? In the sample Sony DVD player above, it only has 10-bit DAC while it has 24-bit DAC.

Thanks for any help & if you have any helpful links it would be appreciated also.
sinned is offline  
Old 09-04-02, 10:57 AM
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The numbers 24bit/192KHz represent obviously the sample size and sample rate and really has nothing to do with what is encoded onto a CD or DVD.

In audio and video you have a analogue wave signal. Consider a standard sine wave which is a nice smooth curve peak to peak.

In the digital realm a nice smooth curve is not possible. That sine wave is a stair-step pattern. The higher your sampling rate is (192KHz) the "tighter" that stair-step pattern becomes making it closer to a smooth curve. Thus higher quality in sound reproduction because it is getting closer to the original wave file.
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Old 09-06-02, 05:37 PM
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I'm not sure I understand why it has nothing to do with the DVD. Isn't the data stored in the DVD already in digital form (bits)? Hence, why does the DAC process differ among the different DVD players? (Obviously, I am much confused here) Thanks.
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