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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: What is the real difference between HDCD and MQA ? posted by 3+4=5 on January 12, 2017 at 10:26:20:
My superficial understanding of both HDCD and MQA is that MQA may utilize a version of HDCD's hiding of extra information in the channel noise floor by disguising it as pseudo-noise. If I correctly recall (which, I may not), HDCD encoded control bits which instructed the DAC's interpolation filter to switch between different filter responses on-the-fly, depending on the moment to moment characteristics of the music content.As I understand it, MQA does not switch between different filter functions. It instead uses the the channel noise floor to hide ultrasonic information bandwidth by folding it down in to the channel as pseudo-noise. In that way, a channel bandwidth can be stored and transported as a file one quarter of it's original size and bandwidth. I believe that MQA utilizes this additional bandwidth to enable the employment of an soft slope, non-brickwall anti-alias filter at recording without violating Nyquist, and a similar filter at playback to minimze interpolation filter impulse response ringing. Not primarily for the purpose of capturing ultrasonic music content. Which maybe is why the ultrasonic band can be encoded at a low enough SNR to appear as noise without reducing the resolution of the audible content.
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Ken Newton
Edits: 01/12/17
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Follow Ups
- RE: What is the real difference between HDCD and MQA ? - knewton 12:34:41 01/12/17 (2)
- RE: What is the real difference between HDCD and MQA ? - AbeCollins 12:52:28 01/12/17 (1)
- RE: What is the real difference between HDCD and MQA ? - knewton 14:47:21 01/12/17 (0)
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