DDSM: Troubleshooting Page

This page provides answers to some frequently asked questions. We hope this information will help if you experience a problem accessing this database. If you have a question that is not adequatly answered here please send your question to us.

What is the correct use of this routine to uncompress the images? Which parameters have to be specified? Or have the images to be uncompressed in a different way? I tried using the information given in the .ics file for image width and height, but a size conflict was reported.

You only need to supply the width and height parameters when you compress images. These values are stored in the compressed image file and are automatically used when the image is being expanded ("uncompressed").

   USAGE:   jpeg -d -s 'image file name'
   EXAMPLE: jpeg -d -s A_0782.RIGHT_MLO.LJPEG

The expanded image is stored as raw binary data in a file that contains no header information. The image dimensions (height and width) are specified in the ASCII format ".ics" file for that case. The data is stored in "row major" format with two bytes per pixel. Depending on your system, you may need to "swap the bytes", when you read in the raw image datafile.

Can I download a full DDSM case in one command with anonymous ftp?

No. You must use ncftp to download a full case directory with one command.

   cd pub/DDSM/cases/cancers/cancer_03
   get -R case1000
This will create the directory case1000 in your local machines working directory and will copy each file contained in the case into your new directory. Please note this particular volume may not always be on line.

Why can't I read the DDSM tape on my 8mm tape drive?

The DDSM tapes are written on 160mXL EXABYTE tapes on a model number 8505XL tape drive. The tape capacity is 7GB because the tapes are not written in a compressed format (the capacity is 14BG when the data is compressed). The tar command was used to write the tapes (i.e. tar -cvf /dev/rmt/0n ./normal_01).

To read the tapes, you must have a drive that is capable of reading the XL (exteded length) tapes. We believe that the tapes can be read with the following models of drives (8505XL, 8700, 8700LT, and the Mammoth 8900).

   tar -xvf 'your drive device'
   tar -xvf /dev/rmt/0n  (this works for us)

EXABYTE has some good information on tape drive compatability.