[QUESTION] Max size for MPEG video

[Davide Cicuta]

Hello,


I know a similar question has been asked in several ways for quite some time, but I really can't find a definite answer for my particular one...


Is there a maximum size for a DICOM file which contains an MPEG video? Practical/performance issues apart, I mean...


I remembered there was a 2GB limit in general, but now I find indications that this "limit" can be passed (some unofficial sources state even beyond 16GB), though I can't find according to what. OW and OB types state that their maximum value depends on the Transfer Syntax.
In Sup. 149 I saw it's stated that "If a video stream exceeds the maximum length of one fragment (approximately 4 GB), it may be sent as multiple SOP Instances."


Can I take 4GB as a maximum file size?

Thank you in advance!

Davide

[Jouke Numan]

Hi Davide,

Short answer: Max is 4 GB - 2 per file. Multiple files can contain parts of the MPEG.

Long answer:

MPEG TS limits the MPEG stream to be stored in one fragment inside the pixeldata. A fragment is stored inside an Item element (FFFE,E000) which
has a length field containing the length as an even 32-bit unsigned value.

This means that maximum length is 4GB - 2.

See PS 3.5:
7.5: Defines format of item element
A.4: For format of pixel data for Encapsulated TS.
8.2.5- 8.2.7: For description of MPEG syntaxes. Contains limitiation "One fragment shall contain the whole XXX bit stream" and also the statement that the MPEG may be split over multiple files. It depends on the viewer if it can handle these multiple parts.

Regards,

Jouke Numan
Software Architect
GE Healthcare

[Marco Eichelberg]

Jouke Numan wrote:

> Short answer: Max is 4 GB - 2 per file. Multiple files can contain parts of the MPEG.

Please note that this restriction applies to the DICOM MPEG transfer syntaxes, but
not to all DICOM transfer syntaxes. A DICOM multiframe image compressed
with JPEG or JPEG 2000 can - at least in theory - be larger than 4 GByte,
although I have never seen a practical example.

Furthermore, the maximum size of 2^32-2 bytes only applies to the MPEG fragment,
not to the actual file size. If the MPEG stream uses the maximum number of bytes
possible, the complete DICOM file will be slightly over 4 GByte large, which
may be an issue with file systems that do not support files larger than 4 GByte,
such as FAT32.

Best regards,
Marco Eichelberg