10.2 Transfer Syntax for a DICOM Default of Lossless JPEG Compression
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## 10.2 Transfer Syntax for a DICOM Default of Lossless JPEG Compression

DICOM defines a default for lossless JPEG Image Compression, which uses a subset of coding Process 14 with a first-order prediction (Selection Value 1). It is identified by Transfer Syntax UID = "1.2.840.10008.1.2.4.70" and shall be supported by every DICOM implementation that chooses to support one or more of the lossless JPEG compression processes. This implies that:

1. If an Application Entity issues an A-ASSOCIATE request where any offered Abstract Syntaxes is associated in one or more Presentation Context with a JPEG lossless compression Transfer Syntax, at least one of the Presentation Contexts that include this Abstract Syntax, shall include the DICOM Default Lossless JPEG Compression Transfer Syntax and the DICOM Default Transfer Syntax (uncompressed).

   ### Note

   Offering Abstract Syntax (AS1) in two Presentation Contexts with Transfer Syntaxes JPEG lossless (JL1) and (JL2) is not valid, but offering AS1-JL1, AS1-JL2, AS1-TSD, and AS1-JLD is valid because the DICOM Default JPEG Lossless Transfer Syntax (JLD) and the DICOM Default Transfer Syntax (TSD) are present in at least one of the Presentation Contexts that are based on Abstract Syntax (AS1).

2. If an Application Entity that supports one or more lossless JPEG Transfer Syntax receives an A-ASSOCIATE indication corresponding to a request that follows the requirements specified in Section 10.2 (a), every Presentation Context related to a given Abstract Syntax cannot be rejected in an A-ASSOCIATE response for the reason that the DICOM Default lossless JPEG Transfer Syntax is not supported.

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