[SOLVED] Behavior of ThumbNailImage Tags (not part of IFD0)

[epet]

**** SOLVED, see explanation below ****
Hi,
I have a problem with ThumbNailImage meta data.
I want to create EXIF thumbnail images within my jpg files. When I'm using the tool ExifThumbnailCreator (found in the internet) everything works fine and a read-out of the IFD0 section delivers the EXIF tags for thumbnail offset (201h) and length (202h). If thumbnail length is present, I'm looking at the JFIF section for width and heigth.

As ExifThumbnailCreator does not offer a command line option, I tried exiftool.
When I'm using exiftool "-ThumbnailImage<=thumb.jpg" the thumbnail will be inserted as well, but I cannot find the offset and length tag within the IFD0 tag table.

Using a hex editor I can find the required length 202h somewhere between the end of the IFD0 section (behind the last EXIF data addressed via offset, for tags with data length > 4) and the begin of the JFIF section.

Is it also a common way, to place the tag thumbnail length outside of the standard IFD0 tag list, addressed by a multiple of 12 bytes from directory start?
Do I have to scan for this tag at the region mentioned above, or is there a defined access mode (similar to IFD0 tag table), which is not yet supported by my program?

Best regards
epet

[epet]

Explanation:
The problem was a bug in my program code. After reading IFD0, I checked for next IFD by Get16u instead of Get32u. This means, I always returned value zero and I didn't recognise IFD1. As ExifThumbnailCreator places the thumbnail length within IFD0 and exiftool within IFD1, I couldn't detect it with both programs.

Sorry for the unnecessary thread.

epet