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You can also make an infinite number of perfect replicas of your CDs. You can carry backups of every CD ever made on a flashdrive that fits in your jeans pocket

You can also make an infinite number of perfect replicas of your CDs. You can carry backups of every CD ever made on a flashdrive that fits in your jeans pocket, then recreate any of them at any time with no degradation in quality. There are some quasi-plausible arguments for vinyl, but arguing that durability is one of them is hilariously myopic.

deleted 7y ago
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optimiz3 7y ago
Sort of - sometimes there's sub-channel data that is very hard to properly replicate; only certain drives even expose that data to correctly extract. Making perfect audio CD image archives is surprisingly hard. E: Specifically I'm talking about the P & Q channels, but this can also include R through W which while technically unused, still contain data in some form.
- paublyrne 7y ago
  What do you mean by "sub-channel"?
  - LegitShady 7y ago
    https://superuser.com/questions/1189222/cd-rom-subchannel-is-different-when-dumping-the-same-disc https://superuser.com/questions/1189222/cd-rom-subchannel-is... more information here
  - optimiz3 7y ago
    https://en.wikipedia.org/wiki/Compact_Disc_subcode https://en.wikipedia.org/wiki/Compact_Disc_subcode Most audio CD extractors do not provide all of this channel data, as only the digital audio is extracted. When a CD is re-burned, the subchannel data is regenerated, but not a bit-for-bit copy of the original. Sounds the same (usually), but sometimes there is metadata, easter-eggs, and what-not that is omitted. Additionally, some copy protection relied on adding corrupted subchannel data which low end CD players would skip, but high end extractors would not. Having the original subchannel data can be key and necessary to determine whether a sector was infact incorrectly extracted or not.
tzs 7y ago
> You can carry backups of every CD ever made on a flashdrive that fits in your jeans pocket Gracenote had 3 598 785 CDs in their database in 2005 [1], so I'll take that as a lower bound on the number of CDs ever made. I don't know what the largest flash drive that will fit in a jeans pocket is, but the largest I was able to find is 2 TB, but SanDisk showed a 4 TB prototype at CES 2019, so I'll go with that. Assuming lossless compression that averages reducing the size of a song by 75%, a 4 TB flash drive could hold 1 662 149.1 minutes of music. Unless the average CD is under 27.7 seconds long, that's not even enough to hold all the CDs known to Gracenote in 2005. Anyone want to do the math if we allow lossy compression to squeeze more in (although I wouldn't consider it a backup of the CDs if lossy)? [1] http://alchemi.co.uk/archives/mus/how_many_cds_ar.html http://alchemi.co.uk/archives/mus/how_many_cds_ar.html
- jacquesm 7y ago
  Storage capacity has been increasing much faster than new CD volume is being created (relatively speaking), so if it isn't true today it soon will be.
- andybak 7y ago
  Perceptually lossless and mathematically lossless are two different things. I'd be happy with the former.
  - Semaphor 7y ago
    But for a backup, you’d want actual lossless compression, wouldn’t you? Not for listening, but for re-encoding.
    - andybak 7y ago
      I think it's something I could tolerate sacrificing if the storage gains were substantial.
- filleokus 7y ago
  If we move the goal post slightly, we could perhaps conceivably fit all 3.5 million CDs (compressed losslessly) on micro SD cards that would fit inside of the volume of a jewel CD case: https://www.wolframalpha.com/input/?i=177.5+cm%5E3%2F%28%28%283598785*700+MB*0.25%29%2F512+GB%29*165+mm%5E3%29 https://www.wolframalpha.com/input/?i=177.5+cm%5E3%2F%28%28%...

deleted 7y ago

[deleted]

optimiz3 7y ago

Sort of - sometimes there's sub-channel data that is very hard to properly replicate; only certain drives even expose that data to correctly extract. Making perfect audio CD image archives is surprisingly hard. E: Specifically I'm talking about the P & Q channels, but this can also include R through W which while technically unused, still contain data in some form.

paublyrne 7y ago
What do you mean by "sub-channel"?
- LegitShady 7y ago
  https://superuser.com/questions/1189222/cd-rom-subchannel-is-different-when-dumping-the-same-disc https://superuser.com/questions/1189222/cd-rom-subchannel-is... more information here
- optimiz3 7y ago
  https://en.wikipedia.org/wiki/Compact_Disc_subcode https://en.wikipedia.org/wiki/Compact_Disc_subcode Most audio CD extractors do not provide all of this channel data, as only the digital audio is extracted. When a CD is re-burned, the subchannel data is regenerated, but not a bit-for-bit copy of the original. Sounds the same (usually), but sometimes there is metadata, easter-eggs, and what-not that is omitted. Additionally, some copy protection relied on adding corrupted subchannel data which low end CD players would skip, but high end extractors would not. Having the original subchannel data can be key and necessary to determine whether a sector was infact incorrectly extracted or not.

tzs 7y ago

> You can carry backups of every CD ever made on a flashdrive that fits in your jeans pocket Gracenote had 3 598 785 CDs in their database in 2005 [1], so I'll take that as a lower bound on the number of CDs ever made. I don't know what the largest flash drive that will fit in a jeans pocket is, but the largest I was able to find is 2 TB, but SanDisk showed a 4 TB prototype at CES 2019, so I'll go with that. Assuming lossless compression that averages reducing the size of a song by 75%, a 4 TB flash drive could hold 1 662 149.1 minutes of music. Unless the average CD is under 27.7 seconds long, that's not even enough to hold all the CDs known to Gracenote in 2005. Anyone want to do the math if we allow lossy compression to squeeze more in (although I wouldn't consider it a backup of the CDs if lossy)? [1] http://alchemi.co.uk/archives/mus/how_many_cds_ar.html http://alchemi.co.uk/archives/mus/how_many_cds_ar.html

jacquesm 7y ago
Storage capacity has been increasing much faster than new CD volume is being created (relatively speaking), so if it isn't true today it soon will be.
andybak 7y ago
Perceptually lossless and mathematically lossless are two different things. I'd be happy with the former.
- Semaphor 7y ago
  But for a backup, you’d want actual lossless compression, wouldn’t you? Not for listening, but for re-encoding.
  - andybak 7y ago
    I think it's something I could tolerate sacrificing if the storage gains were substantial.
filleokus 7y ago
If we move the goal post slightly, we could perhaps conceivably fit all 3.5 million CDs (compressed losslessly) on micro SD cards that would fit inside of the volume of a jewel CD case: https://www.wolframalpha.com/input/?i=177.5+cm%5E3%2F%28%28%283598785*700+MB*0.25%29%2F512+GB%29*165+mm%5E3%29 https://www.wolframalpha.com/input/?i=177.5+cm%5E3%2F%28%28%...