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Barcode encyclopedia : Symbology pdf417
PDF417 (Portable Data File) - Multirow, variable length symbology, high data capacity, error correction included.
Stacked symbology, can be read with linear scanners, laser or two dimensional scanners.
- 1108 bytes
- 1850 characters
- 2710 digits
Large files can be encoded into a series of PDF417 symbols, this symbology name is Macro PDF417.
Major features of PDF417:
- Character set: All 128 ASCII characters, all 128 extended ASCII, 8 bit binary data
- Symbol size: 3 to 90 rows
- Bidirectional encoding: Yes
- Error correction level :0-no error correction to 8 - maximum correction level
- Additional level: Macro PDF417, Truncated PDF417, Global Label Identifier (GLI)
Symbol structure :A typical PDF417 symbol contain 3 to 90 rows, each row consists from lrft to right :
- Leading quiet zone
- Start pattern
- Left row indicator
- 1 to 30 data symbol chracters
- Right row indicator
- Stop pattern
- Trailing quiet zone
Each symbol character can contain 0 - 928 values which is called "codewords".
Symbol character encodation:
- 4 bars and 4 spaces
- total 17 modules - this is name PDF417
- Each bar or space can be 1-6 modules in length
Row encoding : Each row uses character patterns from single cluster : in sequence 0,3,6,0,3,6,0,3,6 ....
ClusterNumber=((RowNumber-1) mod 3)*3
- Three compaction modes
- Text compaction mode - alphanumerics and punctuation
- Binary compaction mode - all 8 bit chracters
- Numeric compaction mode - only digits - high density
- Symbol characters 900-928 are reserved for control purposes.
Global Label Identifier (GLI)GLI 0 - correspondends to ISO 8859-1 character set.It is possible to encode data to other languages.
PDF417 Error Correction Levels
|PDF417 uses Reed Solomon error correction instead of check digits. This error correction allows the symbol to endure some damage without causing loss of data. Recommended a minimum error correction is level 2. The error correction level depends on the amount of data that needs to be encoded, the size and the amount of symbol damage that could occur. See table below for recommened error correction level depened on the amout of the encoded data.||