Hello Tom,
Thank you for your reply.
Yes, parameters set in one module are needed to accessed by other modules.
Since most of the API's of libjpeg have  jpeg_compress_struct as an argument, new members are required to be added in this structure.

Regards,
Swapnil



On Tue, Jun 25, 2013 at 6:37 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
swaps jp <swapsjp@gmail.com> writes:
> When I am trying to add vendor specific members to the structure
> "jpeg_compress_struct" and try to run with standard applications or with
> gstreamer an error is occurs indicating structure size mismatch for the
> above mentioned structure.

Do you really need your own fields inside jpeg_compress_struct itself?
The design intention was that most churn of that sort would happen
within the various module-specific sub-structures and thus not affect
the ABI for clients.

                        regards, tom lane