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Do DVDs offer better error correction than CDs? I know from ripping CDs it can take over an hour per CD to get an accurate rip because the program has to read t

Do DVDs offer better error correction than CDs? I know from ripping CDs it can take over an hour per CD to get an accurate rip because the program has to read the disk multiple times to get the correct data out.

jonhohle 8y ago
Do you have context on this? I’ve been ripping/verifying old CD based games using raw cdrdao and can rip a CD with error correction in a few minutes. I often sell games and use the same method to verify the integrity of the game before sending it off.
- oceanghost 8y ago
  Your rips are full of errors unless the drive you're using has C2 (many do), even then-- you've got a few errors. The only way to get an accurate rip of audio data is to compare it to a known good source. This is why Accurate Rip exists... Source: I've ripped 4000cds :) EDIT: This applies only to audio tracks. Data tracks don't suffer from this issue.
  - Dylan16807 8y ago
    It's worth noting that those problems are entirely caused by drives acting like black boxes, not the CD format itself.
    - jacobush 8y ago
      Sort of though. CD Audio is meant to be played back with a minimal buffer before the DAC and to be kept spinning at a very precise speed. It's more like a digital vinyl record than it is a file system, for instance.
      - Dylan16807 8y ago
        There's enough error detection that if you can actually get access to what bits come off the laser you won't have any major problems making a perfect rip. Your whole-disk alignment might be off by a couple sectors, but that's about it.
  - fireattack 8y ago
    >The only way to get an accurate rip of audio data is to compare it to a known good source That's the only way to confirm you got an accurate rip. It says nothing about how to get the rip in the first place. In my experience, "full of errors" sounds exaggerated. Most of CDs can be easily ripped in 'burst mode' (in EAC) or equivalent in other software and you still get same (exact CRC32) result from AccurateRip DB with no C2 involved (I disabled it), as soon as you set the offset correctly. Disclaimer: I didn't rip 4000 CDs, only hundreds.
    - oceanghost 8y ago
      You are technically correct, which is the best kind of correct :-)
- amluto 8y ago
  Aside from various copy-protected CDs, neither data CDs nor DVDs have the problem that audio CDs have with rip accuracy.
- tomc1985 8y ago
  There's a CD ripper called Exact Audio Copy that has some pretty heavy EC/misread mitigation that, in its most accurate mode, can easily take an hour for a moderately scuffed-up disc It's pretty much the gold standard for bitperfect CD rips amongst the torrent community
  - benbristow 8y ago
    Sounds strange. I thought CDs are digital so whatever is received is exact by definition?
    - ajnin 8y ago
      CDs are a physical media storing digital data. The data is stored in microscopic pits on the disc surface that, like all physical media, can be subject to read errors, due to various imperfections. It has built-in error correction but it is not perfect, so that program reads the same thing multiple times to get statistical confidence that the data is correct.
    - tomc1985 8y ago
      You can distort a digital waveform to the point where a 1 is read as a 0... if you get a perfect read of the disc then sure. But for uncompressed audio, a couple of bits being off here and there won't make much of a difference for most uses. (I'd bet high-speed ripping amplifies this problem) Of course it's not 'bitperfect' at that point but then thats why EAC does so many retries.
    - benj111 8y ago
      Ah, I'm aware of at least one copy protection system where a bit was set so that if read multiple times, would give multiple answers. If you ripped it, it would be read as a definite 1 or 0, but the loader relied on it being read differently on multiple runs.
    - danbruc 8y ago
      When you are playing audio from a CD and there are read errors, you get a worse listening experience if you wait for the CD to spin around a couple more times trying to read the data again causing a pause in the audio than just playing the corrupted data block causing a short glitch in the audio. So that is what CD drives do for audio CDs. The entire format of an audio CD is different from a data CD, the audio tracks are not just files. At least early CD drives did the entire audio processing in the drive and they even used to have a separate audio cable that directly connected the CD drive to the sound card. All this means - or at least meant, I have not ripped CDs in ages - that you have to work pretty hard to get an bit accurate rip of an audio CD because a lot of the processing is done in the drive and the raw bit stream is not easily available to the operating system and applications. Especially error correction - which is best effort for audio CDs and does not guarantee the absence of errors - at least used to happen so early and transparently to the following processing steps that it was very hard to know what happened or did not happen to the data stream.

jonhohle 8y ago

Do you have context on this? I’ve been ripping/verifying old CD based games using raw cdrdao and can rip a CD with error correction in a few minutes. I often sell games and use the same method to verify the integrity of the game before sending it off.

oceanghost 8y ago
Your rips are full of errors unless the drive you're using has C2 (many do), even then-- you've got a few errors. The only way to get an accurate rip of audio data is to compare it to a known good source. This is why Accurate Rip exists... Source: I've ripped 4000cds :) EDIT: This applies only to audio tracks. Data tracks don't suffer from this issue.
- Dylan16807 8y ago
  It's worth noting that those problems are entirely caused by drives acting like black boxes, not the CD format itself.
  - jacobush 8y ago
    Sort of though. CD Audio is meant to be played back with a minimal buffer before the DAC and to be kept spinning at a very precise speed. It's more like a digital vinyl record than it is a file system, for instance.
    - Dylan16807 8y ago
      There's enough error detection that if you can actually get access to what bits come off the laser you won't have any major problems making a perfect rip. Your whole-disk alignment might be off by a couple sectors, but that's about it.
- fireattack 8y ago
  >The only way to get an accurate rip of audio data is to compare it to a known good source That's the only way to confirm you got an accurate rip. It says nothing about how to get the rip in the first place. In my experience, "full of errors" sounds exaggerated. Most of CDs can be easily ripped in 'burst mode' (in EAC) or equivalent in other software and you still get same (exact CRC32) result from AccurateRip DB with no C2 involved (I disabled it), as soon as you set the offset correctly. Disclaimer: I didn't rip 4000 CDs, only hundreds.
  - oceanghost 8y ago
    You are technically correct, which is the best kind of correct :-)
amluto 8y ago
Aside from various copy-protected CDs, neither data CDs nor DVDs have the problem that audio CDs have with rip accuracy.
tomc1985 8y ago
There's a CD ripper called Exact Audio Copy that has some pretty heavy EC/misread mitigation that, in its most accurate mode, can easily take an hour for a moderately scuffed-up disc It's pretty much the gold standard for bitperfect CD rips amongst the torrent community
- benbristow 8y ago
  Sounds strange. I thought CDs are digital so whatever is received is exact by definition?
  - ajnin 8y ago
    CDs are a physical media storing digital data. The data is stored in microscopic pits on the disc surface that, like all physical media, can be subject to read errors, due to various imperfections. It has built-in error correction but it is not perfect, so that program reads the same thing multiple times to get statistical confidence that the data is correct.
  - tomc1985 8y ago
    You can distort a digital waveform to the point where a 1 is read as a 0... if you get a perfect read of the disc then sure. But for uncompressed audio, a couple of bits being off here and there won't make much of a difference for most uses. (I'd bet high-speed ripping amplifies this problem) Of course it's not 'bitperfect' at that point but then thats why EAC does so many retries.
  - benj111 8y ago
    Ah, I'm aware of at least one copy protection system where a bit was set so that if read multiple times, would give multiple answers. If you ripped it, it would be read as a definite 1 or 0, but the loader relied on it being read differently on multiple runs.
  - danbruc 8y ago
    When you are playing audio from a CD and there are read errors, you get a worse listening experience if you wait for the CD to spin around a couple more times trying to read the data again causing a pause in the audio than just playing the corrupted data block causing a short glitch in the audio. So that is what CD drives do for audio CDs. The entire format of an audio CD is different from a data CD, the audio tracks are not just files. At least early CD drives did the entire audio processing in the drive and they even used to have a separate audio cable that directly connected the CD drive to the sound card. All this means - or at least meant, I have not ripped CDs in ages - that you have to work pretty hard to get an bit accurate rip of an audio CD because a lot of the processing is done in the drive and the raw bit stream is not easily available to the operating system and applications. Especially error correction - which is best effort for audio CDs and does not guarantee the absence of errors - at least used to happen so early and transparently to the following processing steps that it was very hard to know what happened or did not happen to the data stream.