Melco D100 Ripping CDs

Audio Gear Talk
91

Thanks!

Let’s go through the same steps as before. First, as Rob notes, the files obviously have radically-different sizes:

% ls -l '06 - Money.flac' '06 Pink Floyd - Money.flac'
-rw-r--r-- 1 distler 49870404 Apr  6  2019 '06 - Money.flac'
-rw-r--r-- 1 distler 67646879 Jun 15  2019 '06 Pink Floyd - Money.flac'

This is for two reasons

  1. FLAC is a (lossless) compressed audio format. If you (or, more precisely, your ripper) use different compression settings, the resulting files will have different sizes. We can’t really compare them until we uncompress the data.
  2. The metadata is, of course, different. So we need to remove the metadata before we can compare the files.
% ffmpeg -y -i '06 - Money.flac' -map_metadata -1 a.wav
% ffmpeg -y -i '06 Pink Floyd - Money.flac' -map_metadata -1 b.wav

Now, they’re exactly the same size:

% ls -l a.wav b.wav
-rw-r--r-- 1 distler 67516590 Dec 20 10:15 a.wav
-rw-r--r-- 1 distler 67516590 Dec 20 10:16 b.wav

At this point, with David’s files, we had a problem: there was a 12ms offset in the way they were padded with silence. In order to compare them, we had to strip the leading/trailing silence. With Rob’s files, we’re luckier. The time-alignment is the same, so we can just skip that step.

% sha256sum a.wav b.wav
064afa4d6a058dc5f20702a44ebd94e5e6f903c8d9b43e6e50c4b09c6ab561da  a.wav
064afa4d6a058dc5f20702a44ebd94e5e6f903c8d9b43e6e50c4b09c6ab561da  b.wav

As expected, they are bit-for-bit identical. Unless one of them was a bad rip, this was a foregone conclusion. They could not have been anything but identical.

Still, sha256 hashes might not convince the sceptic. Perhaps Rob works for the NSA and has found a way to break sha256.

So let’s look at the files in Audacity. Here are the two tracks:

53%20AM
53%20AM2562×1670 1.17 MB

Now we invert the second track:

40%20AM
40%20AM2560×1672 1.19 MB

Finally, we choose Tracks → Mix → Mix and Render:

23%20AM
23%20AM2558×1674 407 KB

Total silence. Either Rob doesn’t work for the NSA, or they haven’t broken sha256. But, either way, yet another confirmation that the two rips are identical.

In choosing between the two rippers, the only difference was the size of the FLAC file produced. Smaller is better, so I suppose the D100 wins. But, given the price of disk space these days, I wouldn’t pay more than $100 for better FLAC compression.

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