SUMMARY K3b is unable to resume an UDF-only disc, or import the UDF file tree from a disc that has ISO9660 but no Joliet or Rock Ridge extensions. Even if the disc has Rock Ridge or Joliet, UDF is necessary to create a new session while importing files that exceed 2 GB. STEPS TO REPRODUCE 1. Create a disc with UDF and ISO9660 only (no Rock Ridge or Joliet), or UDF only. UDF 1.02 is enough for multisessioning (not to be confused with packet writing). 2. Try to import the session OBSERVED RESULT K3b only imports the ISO9660 file names, which are not the original file names. ISO9660 file names are uppercased, shortened, and spaces are replaced with underlines. Even with Joliet or Rock Ridge, files are limited to 2 GB. EXPECTED RESULT Import the UDF file names and resume the session. SOFTWARE/OS VERSIONS Linux Mint 21 ADDITIONAL INFORMATION Note that Windows tools like ImgBurn and CDburnerXP had this ability for a long time.
Another reason to support optional UDF-only multisessioning: Joliet and Rock Ridge struggle with advanced unicode characters such as emoticons, where as UDF supports both 8-bit and 16-bit file name encoding. 8-bit ASCII is used for file names without special characters to save space. UDF specifications can be obtained here: http://www.osta.org/specs/pdf/udf260.pdf (page 11, Compression Algorithm) On Joliet / Rock Ridge, sometimes, files with special characters can be added but a new session can not be created.
For UDF 1.02, the specification is on page 6 (page 13 in the PDF file): http://www.osta.org/specs/pdf/udf102.pdf