HDCD CDs and transcoding

[ac16161]

Interesting discussion. Couple of thoughts.

Transcoding all 16-bit FLAC to WAV24 with the HDCD filter via ffmpeg is good for the HDCD-encoded files, but it may or may not be good for regular 16-bit sources, depending on what the DAC does with the stream? I've never been convinced that packing a 16-bit source into a 24-bit stream actually sounds better with my Linn streamers, in fact I think it sounds worse. But that might depend on my hearing or on how the 16 bits are upsampled by the DAC?

For the very small number of HDCD-encoded titles in my collection, I have previously decoded at the ripping stage with the dbpoweramp utility, I'm curious to compare with in-play conversion via ffmpeg. Anyway, just an observation: I notice that the pre-decoded FLAC files that put the decoded HDCD in a 24-bit container are much smaller than their ALAC equivalents. You can flip back and forth between FLAC and ALAC and see this. Could the FLAC compression algorithm be spotting that the true bit depth is not 24 bit, and able to apply much greater degree of lossless compression than ALAC does? Not knowing any of the technical detail of FLAC vs ALAC, I have always just noticed this as a curiosity. It's a moot point if the file is not pre-decoded.