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An analysis of some tracks, unprocessed, off of CD.

j_j

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#1
There are 3 plots in each image.

The first is a histogram (red) of the actual samples on the CD. Since the image isn't 65536 wide, the histogram plots largest and smallest in each bin, but the bins are calculated per individual level.

The first also includes an upsampled version (blue). Anything over +-1 is an intersample over, and is best described as "a bad thing".

The second is a histogram of a zwicker/fletcher loudness model. It ranges from zero (silent) to 400 (louder than (*&*(&(*). It is a good estimate of loudness, NOT spl. That's a different discussion.

The third is a measure of the flatness of the spectrum. A large negative number indicates a large spectral tilt, a small number closer to flat. Zero == white noise.

The very last plot is a plot of the entirety of a very large corpus of tracks, showing both histograms and extrema.

Some of the extrema are politely described as "very wrong".

Intersample overs make a lot of DAC's choke. Excess loudness sounds bad.

This shows clearly, I think, how 'make it loud' makes the CD, which is technically utterly superior to LP, sound a great deal worse than LP.

And it's all in production demands for "make it loud".

black.jpg
A rock track with lots of compression, but some dynamic range above.
corvus.jpg
The above is a reasonably produced LOUD rock track. Notice the lack of intersample overs, the presence of clipping, and the symmetric shape of the loudness histogram.
fnord.jpg
No, no, 1000 times no below. Intersample overs up the wazoo. TWO clipping levels on the positive side (WTF?)
The above (sorry, board won't let me add comments all the time??? ) is a reasonably produced pop track.
hcn.jpg
mize.jpg
Here is a very quiet, older classical recording (above) How it should be, although the gain on the ADC could be a bit higher.
wtf.jpg
The above is what I refer to as a WTF track. Intersample overs, examples of undithered gain adjustment. Just hard to explain.
total.jpg
 
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amirm

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#2
The above is what I refer to as a WTF track. Intersample overs, examples of undithered gain adjustment. Just hard to explain.
WTF indeed. Does it really have distinct regular bins in its loudness distribution?
 

j_j

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#3
The loudness distribution is quantized to 401 bins, but the actual measure can have any value.

The nastiest thing in that track is the zero probabilities in the actual PCM amplitude distribution. They applied a small gain, just greater than 1, and did not bother to dither. That's about the only way to create the hair-comb effect you see in the amplitude distribution.

The loudness distribution, well, when everything else is so weird, who the (*&(*& knows.
 
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