Signing a PDF/A with a JPG image, invalidates the compliance

I am trying to sign a PDF/A document.

I can't do it with Adobe Acrobat without invalidating the PDF/A compliance. So I am using our tool to sign the file.

When I use a BMP as the graphical represenation of the signature, the file remains compliant, if we use a JPG image the compatibility fails.

The only difference between the two PDF/A files (compliant and incompliant) is the XObject that is different (one is simple neat bmp object, the other is a JPG, with Fileter /DCTDecode etc.).

I would like to know if there is any way I can make the JPG image to work without invalidating the PDF/A compliance, or is it inevitable, as a JPG object has attributes that contradict basic concepts of PDF/A.

Thanks

Tal