I was reading a discussion in another forum about FLAC and 24/96 PCM vinyl rips. The poster was bemused that FLAC was able to get 70% compression of these vinyl rips.

My thought was that there would be more data redundancy on a 24/96 rip of vinyl for FLAC to exploit. Given that a LP might only have a dynamic range of =< 80db and a 24 bit rip allows up to ~ 144db then FLAC could be more concise as it were. Am I hopelessly off target here ?

Well, your idea is right and it applies most definitely with a lossy encoder with reasonable settings (e.g. lame -V 2). FLAC is known to behave very poorly with 24bit/96kHz sources. I have encoded dozens of DVD-A and Blu-ray with FLAC and 70% compression is quite normal. Actually it is on the small side so I guess your theory is correct but in a more conservative way than you might have hoped for

I got some 24/96 vinyl rips from the 'net (shame on me), to test just that. It seems that the compression ratio for these high quality files is less than when encoding CD audio, and I guess that is because in 24/96 files there is much more audio data to compress.

Ivan

The increased noise levels (particularly in the ultrasound) wreak havoc on lossless compression levels.

The solution, of course, is lossyWAV.

Or just save as 16-bit FLAC---you'll only be discarding noise.
Even 15-bit is probably enough for vinyl: norm. to -6dB, dither to 16-bit, then FLAC.

-bandpass

Or, as Axon said, use lossyWAV and then the 24 bit FLAC will take up less space than the 16 bit FLAC without lossyWAV would occupy.