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Raised this question in a thread about another, tangentially related topic. @acbarn gave a nice and very reasonable response, but I was wondering if anyone has actually done any testing or has any specific technical insight:
Question is pretty simple. How much does Apple Music's "Sound Check" volume normalization feature degrade noise performance/effective bit depth?
Since Sound Check is an adjustment in the master volume control and not the music file, it is plausible to hypothesize that the adjustment is done either at 32 bits, or else at whatever bit depth is set for the output in the Audio MIDI utility. But while that is a plausible hypothesis, it's far from certain - it also seems possible that the adjustment could be done at the bit depth of whatever music file is being adjusted, in which case redbook files could be adjusted using only 16 bits.
To my mind - and I am happy to be corrected here - I would say any concerns about Sound Check could therefore be roughly categorized as follows:
- If it's 32 bits, no concerns
- If it's 24 bits, not ideal but almost certainly inaudible, even when adjusting 24-bit content
- if its 16 bits (when playing/adjusting 16-bit content), that could in some cases be an issue, especially depending on whether not the adjustment uses dither.
I would love to know if @Archimago or anyone else has done any actual testing of this, and even if not, I'd be grateful if anyone has any clearer knowledge about Sound Check's under-the-hood operation, or a more evidence-backed sense than me of whether or not it's worth even being concerned about it at all.
Thanks!
[P.S. I searched for this topic before starting this thread and did not see anything responsive to these questions. Apologies if this has been answered elsewhere and I missed it.]
Question is pretty simple. How much does Apple Music's "Sound Check" volume normalization feature degrade noise performance/effective bit depth?
Since Sound Check is an adjustment in the master volume control and not the music file, it is plausible to hypothesize that the adjustment is done either at 32 bits, or else at whatever bit depth is set for the output in the Audio MIDI utility. But while that is a plausible hypothesis, it's far from certain - it also seems possible that the adjustment could be done at the bit depth of whatever music file is being adjusted, in which case redbook files could be adjusted using only 16 bits.
To my mind - and I am happy to be corrected here - I would say any concerns about Sound Check could therefore be roughly categorized as follows:
- If it's 32 bits, no concerns
- If it's 24 bits, not ideal but almost certainly inaudible, even when adjusting 24-bit content
- if its 16 bits (when playing/adjusting 16-bit content), that could in some cases be an issue, especially depending on whether not the adjustment uses dither.
I would love to know if @Archimago or anyone else has done any actual testing of this, and even if not, I'd be grateful if anyone has any clearer knowledge about Sound Check's under-the-hood operation, or a more evidence-backed sense than me of whether or not it's worth even being concerned about it at all.
Thanks!
[P.S. I searched for this topic before starting this thread and did not see anything responsive to these questions. Apologies if this has been answered elsewhere and I missed it.]
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