Macro PDF417 decoding specs

[Guenther Grau]

Hi,

I am working on improving the decoding a PDF417 barcode which contains a Macro PDF417 block. When parsing the code words, I encounter the code word 928, indicating the start of a Macro PDF417 block. With some reverse engineering of a PDF417 encoder, I found that the next two code words must be decoded using the number decoding scheme and represent the sequence number of the Macro PDF417 block.
The code words after that need to be decoded using the text decoding scheme, until either 922 (end of Macro PDF417 block) or 923 (start of optional Macro PDF417 block is encountered). The decoded text is the fileId of the Macro PDF417 block.

I don't have access to the official PDF417 spec, so it would be great if someone could confirm or correct my above working assumptions about the Macro PDF417 encoding :-)
The above method works for the Macro PDF 417 barcodes that I have access to, but I don't know it they will work for all Macro PDF417. E.g. is it possible that the sequence number and the fileId are encoded using different encoding schemes (e.g. binary)?

I haven't been able to find any documentation about how the Macro PDF417 options are encoded/decoded, what kind of options exist and what they are used for. It would be great if someone could give me some information/pointers.

I also wonder how the decoder knows how many barcode images/symbols are required to make a complete Macro PDF417. Is that an option or is that information stored elsewhere.

Thanx in advance for any help!

Best regards,

  Guenther