Hi All,
I hope somebody could help me to understand this FLAC file. The analysis is from SPEK and I don't exactly understand what is that blue 'stuff' from 22kHz down to 18 kHz in the whole file (actually all files on the album have it).
Is this how a lossless file should look like? If you would see any other interesting things please share with me I could then learn something new :)
regards
Most likely shaped dither
Most likely shaped dither
Agreed, this is the most likely explanation. Shaped dithering attempts to "move" most of the quantization noise towards higher frequencies, which are less audible to humans. This spectrogram looks like a textbook example of that.
that blue 'stuff'
Others have pointed at dither. Just to chip in: Blue stuff is around -90 dB, see the scale on the right. Pretty close to silence.
Imprecisely speaking (borderlining on wrong, but you get the idea): about as close as you get to silence for a 16-bit signal, -90 to -96 is "the least significant bit" where you would expect dither to show up.
Also this isn't about FLAC or about any particular lossless codec.
Perhaps this is a bit pedantic as the OP's question has been correctly interpreted and answered, but the dither in that spectrogam is more like deep violet, not blue.