Hi,
I have got the same song twice, but the one is ripped in surround sound and the other in stereo.
It looks like this in Spek:
The 5.1 file shows much lower statistics, but the 5.1 is about 3100 kBit/s and the 2.0 about 800. I'm not familiar with audio files, so can you tell me why this is?
Btw. both are level 0 compressed.
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Last edited by KarMa; 15th Dec 2016 at 18:20.
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Seem 5.1 is less louder and as 24 bit free from noiseshaping. You should align (level) on both - 120dB is approx 20 bit dynamics.
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Yes, I mean the high end of the spectrum. I tried a bit around with Ctrl + Up/Down, but the 5.1 is significantly lower in high-end. I couldn't notice a noise difference. I guess some subliminal sounds are different here. Ok, not that important. But what do you mean by noiseshaping? What is that sky-ish looking area in top of the right graphics? The song was ripped from the same CD, one time 5.1 and the other time 2.0 - and it originally is 5.1.
Btw you say 120 dB is good for 20 bit. What shall I use for 16 and what for 24? -
Well i can confirm your concerns about high frequency energy - those small vertical stripes seem to be higher on CD signal version but i have impression that overall signal level is also higher - you can try to check amplitude statistic - difference between two signal versions (peak to peak and RMS) should be quite significant. I would align both signals before spectral analysis.
Noise shaping is a way to reduce quantization noise at desired part of audible spectrum at a cost of increase of overall noise - this is exactly - as CD use 16 bit and source usually has higher bitdepth then signal need to be re-quantized - to reduce error introduced in a requantization process, additional noise is added (so called dither) and noise shaping is used to improve (reduce perceived noise) quality.
Amplitude statistic should explain differences (i think CD may have reduced dynamics by gain compression and overall signal levels higher - clearly different spectrum).
Bellow is SoX https://sourceforge.net/projects/sox/ spectrum analyzer script - we should be able to see whats going on bellow -120dBFS.
Code:@set dyna=180 @set /a clut=%dyna%/5 @sox --multi-threaded --buffer 524288 -S -V -D "%1" -n spectrogram -z %dyna% -w Kaiser -q %clut% -y 1025 -x 2048 -s -o "%~n1_%dyna%dB.png" stat stats -b 16
Last edited by pandy; 16th Dec 2016 at 14:29.
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The program used to export the stereo flac file used dithering -- hence the high frequency noise.
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