Verification vs. Read MD5 for multi-session CD

[bj.8.trades]

I've recently broached a topic regarding broken reading of multi-session DVDs. The issue I'm about to describe would naturally be expected when the created image file is significantly bigger than what's on the DVD.

 

Reading multi-session CDs works just fine, though. The images can even be mounted by the virtual drive software, MagicDisc, via the .CCD layout file (if you selected the option for creating it along with the image file), with all sessions fully visible to the operating system. Oddly enough, when the same files are mounted by CloneCD (the originator of the .CCD format, as I understand it), the OS only sees the first session.

 

The situation in question is where you read/create such an image file from a multi-session CD, then verify that same CD (without comparing against the image file.) You'll see that the MD5 values don't match...

I 20:35:27 ImgBurn Version 2.5.0.0 started!

I 20:35:27 Microsoft Windows XP Professional (5.1, Build 2600 : Service Pack 3)

I 20:35:27 Total Physical Memory: 2,096,344 KB - Available: 1,629,852 KB

W 20:35:27 SPTD can have a detrimental effect on drive performance.

I 20:35:27 Initialising SPTI...

I 20:35:27 Searching for SCSI / ATAPI devices...

I 20:35:28 Found 4 DVD-ROMs, 2 DVD±RWs and 1 DVD±RW/RAM!

I 22:29:52 Operation Started!

I 22:29:52 Source Device: [2:0:0] HL-DT-ST DVDRAM GSA-H62N CL00 (V:) (ATA)

I 22:29:52 Source Media Type: CD-R (Disc ID: 97m31s07f) (Speeds: 4x, 8x, 16x, 24x)

I 22:29:52 Source Media Sectors: 28,433

I 22:29:52 Source Media Size: 66,874,416 bytes

I 22:29:52 Source Media Volume Identifier: TestCD 01

I 22:29:52 Source Media Volume Set Identifier: 3B5CB38FC4A34C70

I 22:29:52 Source Media Application Identifier: Nero Burning ROM

I 22:29:52 Source Media Implementation Identifier: Nero

I 22:29:52 Source Media File System(s): ISO9660, Joliet, UDF (1.02)

I 22:29:52 Read Speed (Data/Audio): MAX / MAX

I 22:29:52 Hardware Read Error Retries: 2

I 22:29:52 Destination File: E:\Temp\TestCD 01.img

I 22:29:52 Destination Free Space: 69,993,320,448 Bytes (68,352,852 KB) (66,750 MB) (65 GB)

I 22:29:52 Destination File System: NTFS

I 22:29:52 File Splitting: Auto

I 22:29:55 Reading Session 1 of 4... (1 Track, LBA: 0 - 941)

I 22:29:55 Reading Track 1 of 1... (MODE1/2352, LBA: 0 - 941)

I 22:29:58 Reading Session 2 of 4... (1 Track, LBA: 12342 - 13096)

I 22:29:58 Reading Track 1 of 1... (MODE1/2352, LBA: 12342 - 13096)

I 22:30:00 Reading Session 3 of 4... (1 Track, LBA: 19997 - 20776)

I 22:30:00 Reading Track 1 of 1... (MODE1/2352, LBA: 19997 - 20776)

I 22:30:02 Reading Session 4 of 4... (1 Track, LBA: 27677 - 28432)

I 22:30:02 Reading Track 1 of 1... (MODE1/2352, LBA: 27677 - 28432)

I 22:30:08 Image MD5: 1a1c3f1c4096b8e79f99733b844af0b4

I 22:30:08 Exporting Graph Data...

I 22:30:08 Graph Data File: E:\Temp\TestCD 01 R_HL-DT-ST DVDRAM GSA-H62N.ibg

I 22:30:08 Export Successfully Completed!

I 22:30:08 Operation Successfully Completed! - Duration: 00:00:12

I 22:30:08 Average Read Rate: 5,442 KB/s (31.6x) - Maximum Read Rate: 12,384 KB/s (71.9x)

I 22:39:40 Operation Started!

I 22:39:40 Source Device: [2:0:0] HL-DT-ST DVDRAM GSA-H62N CL00 (V:) (ATA)

I 22:39:40 Source Media Type: CD-R (Disc ID: 97m31s07f) (Speeds: 4x, 8x, 16x, 24x)

I 22:39:40 Source Media Sectors: 28,433

I 22:39:40 Source Media Size: 58,230,784 bytes

I 22:39:40 Verify Against Image File: No

I 22:39:40 Read Speed (Data/Audio): MAX / MAX

I 22:39:42 Verifying Session 1 of 4... (1 Track, LBA: 0 - 941)

I 22:39:42 Verifying Track 1 of 1... (MODE1/2048, LBA: 0 - 941)

I 22:39:47 Verifying Session 2 of 4... (1 Track, LBA: 12342 - 13096)

I 22:39:47 Verifying Track 1 of 1... (MODE1/2048, LBA: 12342 - 13096)

I 22:39:50 Verifying Session 3 of 4... (1 Track, LBA: 19997 - 20776)

I 22:39:50 Verifying Track 1 of 1... (MODE1/2048, LBA: 19997 - 20776)

I 22:39:52 Verifying Session 4 of 4... (1 Track, LBA: 27677 - 28432)

I 22:39:52 Verifying Track 1 of 1... (MODE1/2048, LBA: 27677 - 28432)

I 22:39:54 Device MD5: 9afe448ffafa5608abc159015d9562d4

I 22:39:58 Operation Successfully Completed! - Duration: 00:00:14

I 22:39:58 Average Verify Rate: 4,738 KB/s (31.6x) - Maximum Verify Rate: 9,786 KB/s (65.2x)

However, the same test, run on a single-session CD, results in no such discrepancies.

 

Boo-Hoo!!!

 

(I've run the same test with other multi and single session CDs... same story.)

[LIGHTNING UK!]

You mean mouted by Virtual CloneDrive rather than CloneCD I assume? VCD is actually pretty dumb/basic. It doesn't handle multisession at all AFAIK.

 

Read mode calculates the MD5 based on what's written to the image file (including the made up session gaps/padding etc) rather than what's read from the disc.

 

Verify mode is just different because it's based on what's read from the disc and there's stuff you can't read on a multisession disc.

 

I'll see if I can't tweak some of the verify stuff so they come out the same though.

[bj.8.trades]

You mean mouted by Virtual CloneDrive rather than CloneCD I assume? VCD is actually pretty dumb/basic. It doesn't handle multisession at all AFAIK.

Yeah, that's what I meant. You know, they style the product as the finest virtual drive software available… Uh, right!

 

I'll see if I can't tweak some of the verify stuff so they come out the same though.

Thanks! I've seen lots of postings where it's implied these MD5 values don't really matter, and comparing to image files is the only thing that counts, but I find them very useful! (I know there are situations where the values are expected to be different, of course.)