PDF to EPUB Conversion Tools Score Low on Accuracy in VIGC Test
“A good example is the combination of the letters ‘f’ and ‘I’,” continues Hagen. “In the text we wrote, there were the word profiles where the ‘f’ and ‘i’ were replaced by one glyph, the ligature. But in some EPUB files we found ‘profles’ instead of profiles’—the ‘i’ had been dropped.
“Some conversion tools didn’t recognize the ligature and made an incorrect conversion. The automatic use of ligatures is the default in Adobe InDesign—i.e. InDesign will automatically replace certain combinations with the ligature—so you can imagine how often this happens in a document, and how often this will go wrong with some tools. You need to scan the converted files manually to check for missing letters, which simply isn’t feasible.”
Validation misses the mark
According to Hagen, validation tools pose an even bigger problem. “What amazed us the most was the validation of the EPUB files. Validation was a standard practice in our test, a simple way to partially check the quality of the conversion. We used four different validation tools and got different results.
“Some tools could validate one EPUB file, while another tool couldn’t. And the differences were inconsistent too—it wasn’t a case of one tool always being different from the other three. Based on our results, publishers face a big challenge in ensuring EPUB files—and subsequently the ebooks themselves—have been converted accurately.”
The complete report with detailed test results can be purchased from the VIGC. They will also continue their search for good tools for EPUB-creation, to further support publishers and printers.