[Originally posted by alien68 on 2009-02-24 20:21:21-08]
After a modification with Picasa I got the following warnings:
======== IMG_0254.JPG
Warning : [minor] Adjusted MakerNotes base by 36
Warning : Invalid CanonCameraSettings data
Warning : Invalid CanonShotInfo data
Warning : Invalid CanonAFInfo2 data
Warning : Invalid MyColors data
I guess that means that picasa moved the makernotes.
So, I tried to fix the errors with exiftool (great tool !).
I first tried the syntax "exiftool -F36 -tagsfromfile @ -makernotes *.jpg" because in the warning message was mentioned that the base was adjusted by 36.
But after that I still got the following warnings:
======== IMG_0254.JPG
Warning : Invalid CanonCameraSettings data
Warning : Invalid CanonShotInfo data
Warning : Invalid CanonAFInfo2 data
Warning : Invalid MyColors data
I placed the original file back and tried the syntax "exiftool -F -tagsfromfile @ -makernotes *.jpg" (to let exiftool make a guess) but I got the same result (the same warnings from above).
Again I placed the original file back and tried with the syntax "exiftool -F0 -tagsfromfile @ -makernotes *.jpg" and that solved all problems.
When i now run "exiftool -warning *.jpg" everything is fine, I get no warnings.
What could be the reason that using -F did not work and -F0 solved all the problems ?
Was I doing something wrong ?
[Originally posted by exiftool on 2009-02-24 23:32:55-08]
The problem is that Picasa is only partially updating the makernote
offsets. It seems to change most of the offsets correctly, but
neglects to update one crutial offset that represents the original
makernote offset. ExifTool sees that this value is wrong, and
concludes that the makernotes have been incorrectly updated.
What you have done with -F0 is the correct thing to do
in this case. You should report this bug to Picasa. If they don't
fix it soon, I may have to put in some specific logic to look for
this type of problem -- this is actually on my to-do list, but I
haven't had a chance to implement this yet. Keep an eye out
for this in future releases. I think Picasa may use the same Exif
library as ACDSee because I have seen this same problem with
this software too.
In the mean time, if you could send
me a sample image it would be useful. My mail is philharvey66 at gmail.com
Thanks.
- Phil
P.S. You don't have to specify a number with the -F option
to fix by the recommended amount. In this case, -F36 is
equivalent to -F, although -F0 is what you need
here.
[Originally posted by alien68 on 2009-02-25 10:32:39-08]
Hi Phil,
Thank you very much for your fast response and your superb tool.
I have reported the problem to Picasa and will send you as fast as possible a sample image.
Thanks.
[Originally posted by exiftool on 2009-02-26 22:59:41-08]Thanks for the sample image. I have released exiftool 7.70 which
has a patch added to test for an invalid makernote trailer. Honestly,
it would be better if Picasa didn't tamper with the trailer at all. It tries
to do the right thing, but does an incomplete job which is worse than
doing nothing at all.
The new version will issue the following warning instead of
using the makernote trailer to adjust the offsets when it
encounters a file such as this:
[minor] Canon makernote trailer may be invalid (ignored)
- Phil
[Originally posted by exiftool on 2009-02-26 23:03:16-08]
This forum needs an edit feature.
I meant to say "it would be better if Picasa didn't tamper
with the makernotes at all". Not "trailer". It's all or
nothing for Canon makernotes. Either do it right, or don't do it
at all.
- Phil
[Originally posted by exiftool on 2009-02-26 23:26:10-08]
This got me thinking. Maybe I should call this a "footer" and
not a "trailer", since "trailer" has connotations with respect
to the file structure, but this data is attached to the
end of the maker note block. I will think about this, and may
change the wording in this warning for the next release.
- Phil