# Orthanc GDCM Windows, do I need it?

**URL:** https://discourse.orthanc-server.org/t/orthanc-gdcm-windows-do-i-need-it/5704
**Category:** General
**Created:** [April 3, 2025, 6:56am UTC](https://discourse.orthanc-server.org/t/orthanc-gdcm-windows-do-i-need-it/5704 "2025-04-03T06:56:27Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![mex](https://discourse.orthanc-server.org/letter_avatar_proxy/v4/letter/m/4da419/32.png) [@mex](https://discourse.orthanc-server.org/u/mex)
#### Post date: [April 3, 2025, 6:56am UTC](https://discourse.orthanc-server.org/t/orthanc-gdcm-windows-do-i-need-it/5704/1 "2025-04-03T06:56:27Z")

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Hi everyone,

I’m trying to C-STORE a study from Orthanc to another DICOM application.

However I get the error:

> DCMTK was unable to transcode from 1.2.840.10008.1.2.4.70 to one of: 1.2.840.10008.1.2.1  
> Internal error while transcoding to 1.2.840.10008.1.2.1

So I did some googling, and found that 1.2.840.10008.1.2.4.70 = JPEG Lossless, and I also found this [wiki](https://orthanc.uclouvain.be/book/plugins/gdcm.html).

1. Is this error hinting that I need GDCM to handle JPEG lossless transcoding instead of DCMTK?

2. How do I install GDCM on Orthanc in 64-bit Windows?  
Is it already installed by default, since I see OrthancGdcm.dll already appears in the “C:\Program Files\Orthanc Server\Plugins” folder, and I also see it mentioned in the logs.

The wiki seems to suggest otherwise, and seems like it needs to be installed so I followed the [wiki](https://orthanc.uclouvain.be/book/plugins/gdcm.html) and downloaded the 64-bit OrthancGdcm-mainline.dll, and placed it “C:\Program Files\Orthanc Server\Plugins\OrthancGdcm-mainline.dll”

1. With the Orthanc.json file , I already had:

“Plugins” : [“C:\Program Files\Orthanc Server\Plugins”],

Do i need to change it to:

“Plugins” : [“C:\Program Files\Orthanc Server\Plugins”, **“C:\Program Files\Orthanc Server\Plugins\OrthancGdcm-mainline.dll”**],

Thanks!

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### Author: ![alainmazy](https://discourse.orthanc-server.org/user_avatar/discourse.orthanc-server.org/alainmazy/32/1576_2.png) [@alainmazy](https://discourse.orthanc-server.org/u/alainmazy)
#### Post date: [April 4, 2025, 4:50pm UTC](https://discourse.orthanc-server.org/t/orthanc-gdcm-windows-do-i-need-it/5704/2 "2025-04-04T16:50:04Z")

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Hi,

GDCM is already installed by default on Windows if you used the Windows Installers. You can check it on [http://localhost:8042/ui/app/#/settings](http://localhost:8042/ui/app/#/settings)

By default, GDCM will not handle JPEG Lossless because it only handles JP2K. You can update this by adding `1.2.840.10008.1.2.4.70` in the configuration:

```auto
  "Gdcm" : {
    "Enable" : true,
    "RestrictTransferSyntaxes" : [
      "1.2.840.10008.1.2.4.90", // JPEG 2000 Image Compression (Lossless Only)
      "1.2.840.10008.1.2.4.91", // JPEG 2000 Image Compression
      "1.2.840.10008.1.2.4.92", // JPEG 2000 Part 2 Multicomponent Image Compression (Lossless Only)
      "1.2.840.10008.1.2.4.93", // JPEG 2000 Part 2 Multicomponent Image 
Compression
      "1.2.840.10008.1.2.4.70" ////// Added ///////
    ]
  }

```

Note that, DCMTK is supposed to handle JPEG Lossless so, I’m really not sure GDCM will do better.

Best regards,

Alain.

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<div class="post-metadata">

### Author: ![mex](https://discourse.orthanc-server.org/letter_avatar_proxy/v4/letter/m/4da419/32.png) [@mex](https://discourse.orthanc-server.org/u/mex)
#### Post date: [April 17, 2025, 7:23am UTC](https://discourse.orthanc-server.org/t/orthanc-gdcm-windows-do-i-need-it/5704/3 "2025-04-17T07:23:07Z")

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Thanks for clarification. GDCM is indeed installed by default in the Windows installer.  
Solution was to disable inbound and outbound transcoding in the orthanc.json.