Error messages

3.2 Program blocks right after invocation.

3.3 What does "CRC error, sector: n" mean?

3.4 Read errors or wrong image size with -RW/+RW media

3.5 My self-written media is recognized as "DVD-ROM" and rejected.

This warning appears with CD media written in "TAO" (track at once) mode. Some drives report an image size which is 2 sectors too large for such media, producing 2 pseudo read errors at the end of the medium which do not mean data loss in this case.

Since the writing mode can not be determined from the medium, dvdisaster assumes a "TAO" CD if exactly the last two sectors are unreadable, and trims the image accordingly. It is up to you to decide whether this is okay. You can advise dvdisaster to treat these sectors as real read errors by using the --dao option or the preferences tab for reading/scanning.

To avoid these problems, consider using the "DAO / Disc at once" (sometimes also called "SAO / Session at once") mode for writing single session media.

Under old Linux versions (kernel 2.4.x) the program occasionally blocks right after the start and before any actions are carried out. It can not be terminated using Ctrl-C or "kill -9".

Eject the medium to make the program terminate. Insert the medium again and wait until the drive recognizes the medium and spins down. Calling dvdisaster again should work now.

The respective sector could be read, but the checksum of its contents does not match the value noted in the error correction file. Some possible causes are:

• The image has been mounted with write permission and was therefore altered (typical evidence: CRC errors in sector 64 and in sectors 200 to 400).
• The computer has some hardware problems, especially when communicating with its mass storage devices.

Some drives report incorrect image sizes when -RW/+RW media are used. Two common cases are:

Problem:	The drive reports the size of the largest image ever written to the medium, not that of the actual image.
Symptoms:	After erasing a medium it is written with a file sized about 100MB. But the image read back is several GB long and contains the remainings of older images.
Problem:	The drive reports the maximum possible medium capacity (typically 2295104 sectors) instead of the number of actually used sectors.
Symptoms:	When reading beyond a certain point of the medium, only read errors occur, but all files on the medium are still readable and complete.

Possible remedy:

Activate the option Use information from the ISO/UDF file system so that the image size will be determined from the ISO/UDF file system.

If the required ISO/UDF sectors are unreadable when trying to recover damaged media there are two possible workarounds:

• Execute the "Compare" function with only the error correction file being selected/given. Note down the correct image size from the output and restrict the reading range accordingly.
• Simply read in the image with the incorrect (larger) size. When invoking the "Fix" function, answer "OK" when you are asked whether the image should be truncated.

This can have the following reasons:

1. The medium book type has been set to "DVD-ROM".
   In this case the drive must support another way to find out the real medium type. Only then dvdisaster will accept the medium and report it as "DVD-ROM (faked book type)".

   But some drives do not support the recognition of faked book types.

2. Some drives can not tell DVD+R9 (two layers) from DVD-ROM.