Article: Is It Time To Rethink Lossless?

[danadam]

3 hours ago, bbosler said:

Can the original 16/44.1 be reconstructed from a 24/192 upsample? I doubt it.

It depends on a few things so it's not something impossible in principle:

# upsample
sox "02. Fast Car.flac" -b24 "up.wav" rate -s 192000

# downsample
sox -D "up.wav" -b16 "down.wav" rate -s 44100

# compare (subtract one from the other)
sox -m -v 1 "02. Fast Car.flac" -v -1 "down.wav" -n stats
             Overall     Left      Right
..
Pk lev dB       -inf      -inf      -inf
RMS lev dB      -inf      -inf      -inf

 

[danadam]

21 minutes ago, bbosler said:

same peak and rms levels does not mean the files are identical.

Sure, but that's not what the example is showing. It shows that the result of subtracting the up- and downsampled version from the original file is a digital silence. This means that each and every sample in the up- and downsampled version is the same as in the original file.

[danadam]

13 hours ago, The Computer Audiophile said:

In essence, it’s like you added a paragraph to the end of a text file then removed it. Not that your example is wrong, it’s just a very simple, if not unrealistic, exercise.

I thought that was the premise of the question, can you get back the 16/44 original from the 24/192 upsample. The assertion was (and apparently still is) that it's never possible, I showed that it sometimes is. I can agree that steep anti-imaging filter (99% bandwidth, the "-s" option) is probably not something that would be usually used, but I'm not sure if that's what you meant by calling it simple.

 

13 hours ago, bbosler said:

I believe the example is definitely wrong. Peak and rms is not the equivalent of comparing each and every sample. 

Could you explain what makes you think that I only compared peak and rms values of the 2 files? Because once again, that operation did compare each and every sample. Maybe if I split it into separate commands it will be more visible:

# create null file
sox -m -v 1 "02. Fast Car.flac" -v -1 "down.wav" "null.wav"

# show statistics of the null
sox "null.wav" -n stats
             Overall     Left      Right
..
Pk lev dB       -inf      -inf      -inf
RMS lev dB      -inf      -inf      -inf

I can also decompress the flac to wav and compare the files directly:

flac -d "02. Fast Car.flac"

md5sum "02. Fast Car.wav" "down.wav"
efcb88d3e5be874902f03bddac953086  02. Fast Car.wav
efcb88d3e5be874902f03bddac953086  down.wav

diff -s "02. Fast Car.wav" "down.wav"
Files 02. Fast Car.wav and down.wav are identical

 

[danadam]

9 hours ago, Audiophile Neuroscience said:

I have just always thought (assumed) lossless relates to a codec, compression and decompression without loss of any information

I agree.

9 hours ago, Audiophile Neuroscience said:

WAV is lossless because it was never compressed.

Following from the previous, I'd say that "lossless"/"lossy" is just not applicable for WAV 🙂