S/PDIF volume
Feb 18, 2004 at 10:06 PM Thread Starter Post #1 of 7

Prune

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I've one of those cheap DVD players as transport hooked up to an external DAC. The volume control still affects volume. Since I don't think that S/PDIF carries volume information, can I assume that the player is actually changing the sound data? That would mean it's reducing dynamic range!
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Ironic that there's a separate dynamic range menu... Can I assume then that the maximum volume setting (which is the default one too) would be the one sending the unmodified data?
 
Feb 19, 2004 at 2:25 AM Post #5 of 7

aos

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I believe your assumptions are correct.

However, the loss of dynamics might not occur, at least not theoretically. If your signal was 16 bit originally and becomes 24 bit when volume control is not at max, you'd manage to preserve all or some of the dynamics, as the attenuated bits instead of being lost get shifted into less significant bits between 16 and 24. If the signal was 16 and stays 16 after attenuation then yes it would lose dynamic range.
 
Feb 20, 2004 at 2:25 AM Post #6 of 7

maczrool

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So what do such 24-bit DACs as the PCM1791 which have built-in digital filters with digital attenuators do with 16-bit data? Do they convert it to 24-bit when performing such attentuation, thus sparing loss of signal to noise and dynamic range?

Stu
 
Feb 20, 2004 at 4:16 AM Post #7 of 7

aos

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I would imagine that's exactly what they do. I haven't looked at datasheets regarding this though but that would be the most logical implementation. Of course, 24 bit signal would lose some resolution but in reality even the best modern recordings can't reach 24-bit performance.

That doesn't mean that it works that way though.
 

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