Материал: part05

10 Transfer Syntax​

A Transfer Syntax is a set of encoding rules able to unambiguously represent one or more Abstract Syntaxes. In particular, it allows​ communicating Application Entities to negotiate common encoding techniques they both support (e.g., byte ordering, compression,​ etc.). A Transfer Syntax is an attribute of a Presentation Context, one or more of which are negotiated at the establishment of an​ Association between DICOM Application Entities. This Association negotiation is specified in PS3.8 and discussed in PS3.7.​

The selection of a Transfer Syntax applies to the encoding rules for the Data Set portion of a DICOM Message only. All DICOM​ Standard and Private Transfer Syntaxes implicitly specify a fixed encoding for the Command Set portion of a DICOM Message as​ specified in PS3.7.​

This Part of the DICOM Standard defines standard DICOM Transfer Syntaxes and assigns a unique Transfer Syntax Name to each​ one.ThestandardDICOMTransferSyntaxesarespecifiedinAnnexA.TheDICOMnotationforTransferSyntaxnamesisthenotation​ used for UIDs (see Section 9).​

The organization responsible for the definition and registration of DICOM Transfer Syntaxes is NEMA. NEMA guarantees uniqueness​ for all DICOM Transfer Syntax Names.​

Privately defined Transfer Syntax Names may also be used; however, they will not be registered by NEMA. Organizations that define​ private Transfer Syntax Names shall follow the registration process defined in Section 9.2.​

10.1 DICOM Default Transfer Syntax​

DICOM defines a default Transfer Syntax, the DICOM Implicit VR Little Endian Transfer Syntax (UID = "1.2.840.10008.1.2 "), which​ shall be supported by every conformant DICOM Implementation. This implies that:​

a.​If an Application Entity issues an A-ASSOCIATE request, it shall offer the DICOM Implicit VR Little Endian Transfer Syntax in at​ least one of the Presentation Contexts associated with each offered Abstract Syntax.​

Note​

Offering Abstract Syntax (AS1) in two Presentation Contexts with Transfer Syntaxes (TS1) and (TS2) is not valid, but​ offering AS1-TS1, AS1-TS2 and AS1-TSD is valid because the DICOM Default Little Endian Transfer Syntax (TSD) is​ present in at least one of the Presentation Contexts that are based on Abstract Syntax (AS1).​

b.​If an Application Entity receives an A-ASSOCIATE indication corresponding to a request that follows the requirements specified​ inSection10.1(a),everyPresentationContextrelatedtoagivenAbstractSyntaxcannotberejectedinanA-ASSOCIATEresponse​ for the reason that none of the Transfer Syntaxes are supported.​

Both of these requirements, (a) and (b), are waived when the Application Entity sending the pixel data has only access to the pixel​ data in lossy compressed form or the pixel data in a lossless compressed form that is of such length that it cannot be encoded in the​ default Transfer Syntax, and a Transfer Syntax that uses a pixel data reference is not offered.​

Requirement (b) to accept the default Transfer Syntax is waived if a Transfer Syntax that uses a pixel data reference is offered.​

Note​

In other words, every sending AE is required to be able to convert any Data Set it is going to transmit into the default​ Transfer Syntax, regardless of the form in which it originally received or stored the Data Set, except in the cases of when​ the decompressed Pixel Data is too large to encode in the default Transfer Syntax or is received in a lossy compressed​ form. In the case of lossy compressed Pixel Data, the sending AE is permitted to propose only the lossy compressed​ Transfer Syntax appropriate to the lossy form that was received. In the case of lossless compressed Pixel Data that is too​ largetoencodeinthedefaultTransferSyntax,thesendingAEispermittedtoproposeanyappropriatelosslesscompression​ Transfer Syntax, not necessarily that in which the image was received, as an alternative to the default Transfer Syntax.​

This waiver does not apply to Data Sets received in a lossless compressed form if the decompressed Pixel Data is small​ enough to encode in the default Transfer Syntax, which means that any AE receiving a Data Set in a lossless compressed​ Transfer Syntax that needs to re-send the Data Set is required to be able to decompress it in order to support (at least) the​ default Transfer Syntax.​

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Similar concerns apply to the Web Services transactions and are addressed by specific requirements in PS3.18.​

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

DICOMdefinesadefaultforlosslessJPEGImageCompression,whichusesasubsetofcodingProcess14withafirst-orderprediction​ (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 imple-​ mentation that chooses to support one or more of the lossless JPEG compression processes. This implies that:​

a.​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).​

b.​If an Application Entity that supports one or more lossless JPEG Transfer Syntax receives an A-ASSOCIATE indication corres-​ ponding to a request that follows the requirements specified in Section 10.2 (a), every Presentation Context related to a given​ AbstractSyntaxcannotberejectedinanA-ASSOCIATEresponseforthereasonthattheDICOMDefaultlosslessJPEGTransfer​ Syntax is not supported.​

10.3 Transfer Syntaxes for a DICOM Default of Lossy JPEG Compression​

DICOM defines defaults for Lossy JPEG Image Compression, one for 8-bit images and the other for 12-bit images. JPEG coding​ Process 1 (identified by Transfer Syntax UID = "1.2.840.10008.1.2.4.50 ") is used for 8-bit images. JPEG coding Process 4 (identified​ by Transfer Syntax UID = "1.2.840.10008.1.2.4.51 ") is used for 12-bit images. This implies that:​

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

Note​

Offering Abstract Syntax (AS1) in two Presentation Contexts with Transfer Syntaxes JPEG lossy (JL1) and (JL2) is not​ valid, but offering AS1-JL1, AS1-JL2 and AS1-JLD is valid because the DICOM Default JPEG Lossy Transfer Syntax​ (JLD) is present in at least one of the Presentation Contexts that are based on Abstract Syntax (AS1).2. The DICOM​ Default Transfer Syntax (uncompressed) may be offered if the sender has access to the original pixel data in an uncom-​ pressed or lossless compressed form.​

b.​If an Application Entity that supports one or more Lossy JPEG Transfer Syntaxes receives an A-ASSOCIATE indication corres-​ ponding to a request that follows the requirements specified in Section 10.3 (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 lossy JPEG Transfer​ Syntax is not supported.​

Note​

The12bitdefaultTransferSyntax1.2.840.10008.1.2.4.51canalsobeusedtoencode8bitimages,butthebitstreamrequired​ is not identical to that used in the 8 bit default Transfer Syntax 1.2.840.10008.1.2.4.50 (see A.4.1).​

10.4 Transfer Syntax For DICOM RLE Image Compression​

DICOM defines the RLE Image Compression (see Annex G). This implies that:​

a.​If an Application Entity issues an A-ASSOCIATE request where any offered Abstract Syntaxes is associated in one or more​ PresentationContexts(s)withRLEcompressionTransferSyntax,atleastoneofthePresentationContextsthatincludethisAbstract​ Syntax, shall include the DICOM Default Transfer Syntax (uncompressed).​

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10.5TransferSyntaxForADICOMDefaultofLosslessandLossy(Near-lossless)​ JPEG-LS Compression​

OneTransferSyntaxisspecifiedforJPEG-LSLosslessImageCompression,andoneTransferSyntaxisspecifiedforJPEG-LSLossy​ (Near-Lossless) Image Compression. The JPEG-LS Lossless Transfer Syntax shall be supported as a baseline if the JPEG-LS Lossy​ (Near-Lossless) Transfer Syntax is supported.​

10.6 Transfer Syntax For JPEG 2000 Compression​

One Transfer Syntax is specified for JPEG 2000 Image Compression (Lossless Only), and one Transfer Syntax is specified for JPEG​ 2000 Image Compression. Either of these may be negotiated separately and there is no default or baseline specified (other than de-​ scribed in Section 10.1).​

Note​

1.​All JPEG 2000 codecs are required by [ISO/IEC 15444-1] to support both reversible and irreversible wavelet and multi-​ component transformations. The reason for specifying two separate Transfer Syntaxes in DICOM is to allow an applic-​ ation to request the transfer of images in a lossless manner when possible. The JPEG 2000 Image Compression​ Transfer Syntax allows for either lossless or lossy compression to be used at the sender's discretion.​

2.​No baseline using other compression schemes is required.​

3.​When the pixel data has been received in the JPEG 2000 Image Compression Transfer Syntax, since it may have been​ lossy compressed, the waiver of the requirement in Section 10.1 to support the DICOM default Transfer Syntax still​ applies.​

Inaddition,oneTransferSyntaxisspecifiedforJPEG2000Multi-componentImageCompression(LosslessOnly)withMulti-Component​ Transformation Extensions, and one Transfer Syntax is specified for JPEG 2000 Multi-component Image Compression with Multi-​ Component Transformation Extensions. Either of these may be negotiated separately and there is no default or baseline specified​ (other than described in Section 10.1).​

Note​

JPEG 2000 codecs that support the Part 2 JPEG 2000 Multi-Component Transformation Extensions are required to support​ all the multi-component extensions as described in Annex J of [ISO/IEC 15444-2]. This includes both array based transform-​ ations and the 9-7 and 5-3 wavelet transformations that are also used in Part 1 of JPEG 2000. This also includes component​ reordering, component collections and application of more than one multi-component transformation in succession.​

10.7 Transfer Syntax For MPEG2 Main Profile / Main Level Video Compression​

One Transfer Syntax is specified for MPEG2 Main Profile / Main Level Video Compression.​

10.8 Transfer Syntax For JPIP Referenced Pixel Data​

Two Transfer Syntaxes are specified for JPIP Referenced Pixel Data.​

The persistence of the references in objects transferred with one of these Transfer Syntaxes is not defined. That is, applications​ should make no assumptions as to the timeframe when the referenced pixel data will be available. Due to the indeterminate time that​ the URL remains valid, it may be inappropriate to cache the URL. Because the pixel data may not have been retrieved in its entirety​ or full fidelity, it may be inappropriate to use this Transfer Syntax for the purpose of permanent storage or to reference such instances​ in Storage Commitment and Performed Procedure Step service classes.​

These Transfer Syntaxes shall not be used for media storage defined by PS3.10.​

10.9 Transfer Syntax For MPEG2 Main Profile / High Level Video Compression​

One Transfer Syntax is specified for MPEG2 Main Profile / High Level Video Compression.​

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10.10 Transfer Syntax For MPEG-4 AVC/H.264 High Profile / Level 4.1 Video​ Compression​

One Transfer Syntax is specified for MPEG-4 AVC/H.264 High Profile / Level 4.1 Video Compression and one Transfer Syntax is​ specified for MPEG-4 AVC/H.264 BD-compliant High Profile / Level 4.1. Transfer Syntax MPEG-4 AVC/H.264 High Profile / Level​ 4.1 corresponds to the ITU-T H.264 standard's profile and level specifications. Transfer Syntax MPEG-4 AVC/H.264 BD-compliant​ High Profile / Level 4.1 corresponds to a restricted set of spatial and temporal resolutions described Table 8-4. This Transfer Syntax​ limits the ITU-T H.264 High Profile / Level 4.1 to HD video formats that are supported by Blu-ray™ (BDRWP 2.B).​

10.11 Transfer Syntaxes for MPEG-4 AVC/H.264 High Profile / Level 4.2 Video​ Compression​

One Transfer Syntax is specified for MPEG-4 AVC/H.264 High Profile / Level 4.2 for 2D Video Compression and one Transfer Syntax​ is specified for MPEG-4 AVC/H.264 High Profile / Level 4.2 for 3D Video Compression. Transfer Syntax MPEG-4 AVC/H.264 High​ Profile / Level 4.2 for 2D Video Compression corresponds to the ITU-T H.264 standard's profile and level specifications except that​ the use of frame packing formats for 3D video is not allowed as defined in Table 8-8. Transfer Syntax MPEG-4 AVC/H.264 High​ Profile / Level 4.2 for 3D Video Compression corresponds to the ITU-T H.264 standard's profile and level specifications. It should be​ used for transmitting stereoscopic 3D content with frame packing formats as defined in Table 8-8.​

10.12 Transfer Syntax For MPEG-4 AVC/H.264 Stereo High Profile / Level 4.2​ Video Compression​

One TransferSyntaxis specified for MPEG-4AVC/H.264 StereoHighProfile / Level4.2 Video Compression. TransferSyntaxMPEG-​ 4 AVC/H.264 Stereo High Profile corresponds to the ITU-T H.264 standard's profile and level specifications.​

10.13TransferSyntaxforHEVC/H.265MainProfile/Level5.1VideoCompression​

One Transfer Syntax is specified for HEVC/H.265 Main Profile / Level 5.1 Video Compression. Transfer Syntax HEVC/H.265 Main​ Profile corresponds to the [ISO/IEC 23008-2] HEVC standard's profile and level specifications.​

10.14TransferSyntaxforHEVC/H.265Main10Profile/Level5.1VideoCompres-​ sion​

One Transfer Syntax is specified for HEVC/H.265 Main 10 Profile / Level 5.1 Video Compression. Transfer Syntax HEVC/H.265 Main​ 10 Profile corresponds to the [ISO/IEC 23008-2] HEVC standard's profile and level specifications.​

10.15TransferSyntaxforSMPTEST2110-20UncompressedProgressiveActive​ Video​

This Transfer Syntax is used for Uncompressed Video pixels carried in a DICOM-RTV Flow (separated from DICOM-RTV Metadata​ Flow) as described by [SMPTE ST 2110-20], in the case the video is progressive (e.g., 1080p). The main parameters of the transfer​ syntax are described in Section A.8.​

10.16 Transfer Syntax for SMPTE ST 2110-20 Uncompressed Interlaced Active​ Video​

This Transfer Syntax is used for Uncompressed Video pixels carried in a DICOM-RTV Flow (separated from DICOM-RTV Metadata​ Flow) as described by [SMPTE ST 2110-20], in the case the video is interlaced (e.g., 1080i). The main parameters of the transfer​ syntax are described in Section A.9.​

10.16.1 Interlaced Vs. Progressive Video​

Interlaced video supports transmitting video with a smaller bandwidth. One frame contains only odd lines and the next one contains​ only even lines. Interlaced video is acceptable for display but may cause problems in image processing. It is recommended to use​

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progressive video. However, in case an original interlaced video signal is converted in the DICOM-RTV format, it is recommended to​ maintain the interlaced format and let the processing application deal with it.​

10.17 Transfer Syntax for SMPTE ST 2110-30 PCM Digital Audio​

This Transfer Syntax is used for audio channel data carried in a DICOM-RTV Flow (separated from DICOM-RTV Metadata Flow) as​ described by [SMPTE ST 2110-30]. The main parameters of the transfer syntax are described in Section A.10.​

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