KSTR
Major Contributor
Comparing file sizes isn't that meaningful as it all depends on the algorithm. An endless repetition of the same 48 sample values is of course easy to detect and pack. 7zip reduces it to 400bytes(undithered) and 90kB(dithered). FLAC was created to have a simple to implement (fixed point) and fast unpacking scheme that also is compatible with streaming, it's not optimized for making best use of inherent redundancy.
Since dither is a PWM submodulation of a PCM stream it of course retains information that would be lost otherwise when reducing bit depth or manipulating the data (even a simple level change requires a re-dither). That submodulation is harder to compress.
Note that adding a noise signal later to an undithered output (that was obtained by truncation or rounding) does not retain information although it almost looks the same like true dither and also shows the same compression ratio mismatches. File size difference tells us nothing in the end.
Since dither is a PWM submodulation of a PCM stream it of course retains information that would be lost otherwise when reducing bit depth or manipulating the data (even a simple level change requires a re-dither). That submodulation is harder to compress.
Note that adding a noise signal later to an undithered output (that was obtained by truncation or rounding) does not retain information although it almost looks the same like true dither and also shows the same compression ratio mismatches. File size difference tells us nothing in the end.
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