Problem in DNG Converter while processing Sony's ARW images

[Christoph_CQ]

In all versions of DNG Converter I tested (V12.3 til V16.2) the DNG converter badly converts the Sony's ARW images. ARW images contain SR2 data described in the SR2 IFD. This IFD contains two important tags: SR2PrivateDataOffset (0x7200) and SR2PrivateDataLength (0x7201). This 'SR2 Private Data' is decrypted using the SR2PrivateIFDKey (0x7221). See the original SR2 IFD content below:

As shown in the picture above, the size of the SR2 PrivateData block only is 0xA74A.

The DNG Converter create for the SR2 data an 'SR2 ' entry in the DNG PrivateData tag (0xC634). The size of this PrivateData entry is set to the original SR2PrivateDataLength value (here 0xA74A).

The bug is - that the Converter writes to the DNG PrivateData tag not only the SR2 PrivateData, but also the whole SR2 IFD and the SR2 PrivateData. Due to this bug, the DNG PrivateData buffer is not long enough to store the SR2 IFD and SR2 PrivateData.

This picture shows the SR2 IFD created from the DNG PrivateData tag. The 0x7250 tag is already marked as <not valid data>, because the buffer is too short. Also the SR2PrivateData content cannot be properly processed, because the buffer is too short.

Two ways to fix the problem:

1. Store the (encoded) SR PrivateData content in the DNG PrivateData tag only (size remains unchanged as specified by the DNGPrivateIFDLength value)
2. Calculate properly the required size to store the SR2 IFD and the SR2 PrivateData content. This will increase the required space and depends on other content defines in the SR2 IFD like IDC1_IFD, IDC2_IFD, MRWInfo etc.