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Topic: EAC vs. ImgBurn gap detection (Read 4684 times) previous topic - next topic
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EAC vs. ImgBurn gap detection

I ripped a CD of Ashkenazy's Chopin Etudes with each of them, and got the following cue sheets:

*** EAC ***

Code: [Select]
REM DISCID A60EC70C
REM COMMENT "ExactAudioCopy v1.0b2"
CATALOG 0028941412720
PERFORMER "Unknown Artist"
TITLE "Unknown Title"
FILE "Image.wav" WAVE
  TRACK 01 AUDIO
    TITLE "Track01"
    PERFORMER "Unknown Artist"
    ISRC GBF077230601
    INDEX 00 00:00:00
    INDEX 01 00:00:32
  TRACK 02 AUDIO
    TITLE "Track02"
    PERFORMER "Unknown Artist"
    ISRC GBF077230603
    INDEX 00 03:20:72
    INDEX 01 03:23:42
  TRACK 03 AUDIO
    TITLE "Track03"
    PERFORMER "Unknown Artist"
    ISRC GBF077230605
    INDEX 00 09:52:19
    INDEX 01 09:53:65
  TRACK 04 AUDIO
    TITLE "Track04"
    PERFORMER "Unknown Artist"
    ISRC GBF077230607
    INDEX 00 15:41:42
    INDEX 01 15:42:47
  TRACK 05 AUDIO
    TITLE "Track05"
    PERFORMER "Unknown Artist"
    ISRC GBF077230609
    INDEX 00 19:34:69
    INDEX 01 19:36:20
  TRACK 06 AUDIO
    TITLE "Track06"
    PERFORMER "Unknown Artist"
    ISRC GBF077230611
    INDEX 00 24:14:59
    INDEX 01 24:17:72
  TRACK 07 AUDIO
    TITLE "Track07"
    PERFORMER "Unknown Artist"
    ISRC GBF077230701
    INDEX 00 29:29:64
    INDEX 01 29:39:07
  TRACK 08 AUDIO
    TITLE "Track08"
    PERFORMER "Unknown Artist"
    ISRC GBF077230703
    INDEX 00 34:27:17
    INDEX 01 34:29:65
  TRACK 09 AUDIO
    TITLE "Track09"
    PERFORMER "Unknown Artist"
    ISRC GBF077230705
    INDEX 00 37:56:39
    INDEX 01 38:00:22
  TRACK 10 AUDIO
    TITLE "Track10"
    PERFORMER "Unknown Artist"
    ISRC GBF077230707
    INDEX 00 43:43:24
    INDEX 01 43:46:17
  TRACK 11 AUDIO
    TITLE "Track11"
    PERFORMER "Unknown Artist"
    ISRC GBF077230709
    INDEX 00 50:39:17
    INDEX 01 50:42:40
  TRACK 12 AUDIO
    TITLE "Track12"
    PERFORMER "Unknown Artist"
    ISRC GBF077230711
    INDEX 00 56:24:67
    INDEX 01 56:28:30
*** IMGBURN ***

Code: [Select]
CATALOG 0028941412720
FILE "Image.wav" WAVE
  TRACK 01 AUDIO
    ISRC GBF077230601
    INDEX 00 00:00:00
    INDEX 01 00:00:32
  TRACK 02 AUDIO
    ISRC GBF077230603
    INDEX 00 03:20:73
    INDEX 01 03:23:42
  TRACK 03 AUDIO
    ISRC GBF077230605
    INDEX 00 09:52:20
    INDEX 01 09:53:65
  TRACK 04 AUDIO
    ISRC GBF077230607
    INDEX 00 15:41:43
    INDEX 01 15:42:47
  TRACK 05 AUDIO
    ISRC GBF077230609
    INDEX 00 19:34:70
    INDEX 01 19:36:20
  TRACK 06 AUDIO
    ISRC GBF077230611
    INDEX 00 24:14:60
    INDEX 01 24:17:72
  TRACK 07 AUDIO
    ISRC GBF077230701
    INDEX 00 29:29:65
    INDEX 01 29:39:07
  TRACK 08 AUDIO
    ISRC GBF077230703
    INDEX 00 34:27:18
    INDEX 01 34:29:65
  TRACK 09 AUDIO
    ISRC GBF077230705
    INDEX 00 37:56:40
    INDEX 01 38:00:22
  TRACK 10 AUDIO
    ISRC GBF077230707
    INDEX 00 43:43:25
    INDEX 01 43:46:17
  TRACK 11 AUDIO
    ISRC GBF077230709
    INDEX 00 50:39:18
    INDEX 01 50:42:40
  TRACK 12 AUDIO
    ISRC GBF077230711
    INDEX 00 56:24:68
    INDEX 01 56:28:30
As you can see, each of the INDEX 00 values differs by 0:00:01. (Yes, I'm OCD about these things.) I've tried EAC on A and B gap detection modes, with the same results (C stalls). I've tried ImgBurn on 1-2-3, 1-3-2, and 3-1-2 modes with the same results (the others stall). For most of my other CDs, EAC and ImgBurn match perfectly on A and 1-2-3 modes, my default settings respectively. Intuitively it seems like I should trust EAC because it's more advanced, but the last and only other time they didn't match, EAC was horribly off by several minutes on a track while ImgBurn was correct (or at least a reasonable value). From your experiences, which cue sheet would you trust?

EAC vs. ImgBurn gap detection

Reply #1 –
Unless my understanding of gaps is completely wrong, there is  no way to know for sure which is right. Regrettably, it's just one more uncertainty about CD ripping that you'll have to live with.

EAC vs. ImgBurn gap detection

Reply #2 –
Just wondering, how is gap information (i.e. the INDEX 00) stored on a CD? Based on my tests, there seems to be a contradiction. If gap information is stored in the metadata, then it would simply be read out, and there would be no ambiguity or need for gap detection. On the other hand, I have ruled out the possibility that gap information is not stored on a CD at all: I made two copies of the same WAV and CUE file, and modified the INDEX 00 values for one of the CUE files, then burned them both. When re-ripping the burned CDs, I found that they were indeed different. Then the information must be stored somehow in the audio portion? But then since I used identical WAV files, they should have produced identical CDs.

EAC vs. ImgBurn gap detection

Reply #3 –
The CD has a table of contents (TOC) in the lead-in, and it does have some metadata, but it mainly only just points to the sector where each track's index 01 should begin. This is what is used for the initial display of track durations and for jumping from track to track.

The audio data comes after the lead-in, and is multiplexed with error correction info plus several other data streams called sub-channels or subcode channels. One of the subcode channels (Q) contains all kinds of stuff, including the track and index numbers and timecode. This is the info that a CD player uses for its track & time display, and is the only place where pregap info is found.

The ripper doesn't have access to the raw multiplexed data. CD drives demux it in the hardware & firmware, and only provide software access to interpreted streams. The ripper can ask for the audio data only, or the subcode only. I don't know any technical details, but based on comments I've seen by the developers of cdrtools, PerfectRip, and CUETools, it seems that subcode-reading is an inexact science with variable support in CD drives, which is why you can get different results from different drives or different reading methods, or even from read to read on the same drive. I also saw a mention that the subcode data is sometimes offset from the audio data it corresponds to.

If you only changed index 00 locations in the cue sheet, it should not result in different audio files between CDs burned otherwise identically and ripped without error. You should provide more info about your burning and ripping process and how exactly the cue sheets and ripped audio files differ. EAC has a WAV comparison tool (ctrl+W) that can help. Before using it, go to the WAV editor options (Alt+Q), Compare tab, and make sure "Determine differences more exactly" is checked. Also when doing the rips, make sure you don't have Normalize enabled in the EAC options.

EAC vs. ImgBurn gap detection

Reply #4 –
I compared the WAVs and they are completely identical. Only the ripped CUE sheets are different, and each ripped CUE sheet matches the CUE sheet I used to burn onto each disc exactly. That is, the INDEX 01 are intact (because I didn't change them), but my changes to the INDEX 00 in the doctored one do show up.

EAC vs. ImgBurn gap detection

Reply #5 –
First post...want to chime in with some information and pose some more questions.

Quote from: Cynic on
Unless my understanding of gaps is completely wrong, there is  no way to know for sure which is right. Regrettably, it's just one more uncertainty about CD ripping that you'll have to live with.


Of course there's one way to know what is right - burn a CD-R with known gaps and then attempt to detect those gaps. If the gaps don't match what you burned, something is wrong.

Quote from: mjb2006 on
The ripper doesn't have access to the raw multiplexed data. CD drives demux it in the hardware & firmware, and only provide software access to interpreted streams. The ripper can ask for the audio data only, or the subcode only. I don't know any technical details, but based on comments I've seen by the developers of cdrtools, PerfectRip, and CUETools, it seems that subcode-reading is an inexact science with variable support in CD drives, which is why you can get different results from different drives or different reading methods, or even from read to read on the same drive. I also saw a mention that the subcode data is sometimes offset from the audio data it corresponds to.


This is going back to ancient times in computer land, but I still have a Mac that runs OS 9, and on it I have a copy of ASTARTE CD-Copy. It has always seemed faster and more reliable than EAC for gap detection. I often come across discs where EAC will hang while trying to detect a gap, but CD-Copy flies right through. I've even gone as far as physically moving drives from my Mac to a PC, and while they work fine under CD-Copy, they all have the same issues in EAC with certain discs. Switching EAC modes and/or switching to Inaccurate will *usually* let me get through a disc, but not always, and usually if I have to do that the gap in question is incorrect. I'm not sure CD-Copy was perfect, but it would sure be interesting to know how it did gap detection.

Thoughts?