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    Batch JPEG lossless operation problems

    Hello!

    I recently found out that I can apply lossless JPEG operations to large numbers of files at once, through selecting them in the thumbnail viewer. I noticed that it seems like even if you select all the images in a folder, it only will actually apply the operation to the ones whose thumbnails have been generated already (as it can sometimes take a little while for the previews to be made, so sometimes not all of the selected files will have a generated thumbnail). This isn't a very serious issue, because you can get around it by just waiting a short while for all the thumbnails to be done.

    However, I recently encountered a more serious issue while using this feature. I had two folders of pictures that I wanted to apply some JPEG lossless operations to -- in this instance, it was the one to auto-rotate based on EXIF data. I opened the thumbnail viewer for one folder, and got it running on that set of pictures. Then, deciding I could just let my computer be busy for a while, I tried to do the same for the other folder, opening a new instance of irfanview, and applying the same operation to that set of pictures. They were busy for a while, and eventually finished successfully, reporting no problems. However, on looking through the pictures afterwards, there was complete mayhem. Pictures from one folder were now in the other, quite a few had streaks of color blocking out half the image, and some weren't even recognized as images anymore. The folder that I had started the process on first only had the corruption later in the directory, which seems to implicate that the corruption began when it was both processes running at once.

    I have been able to restore all my pictures entirely, because I was able to recover the originals from other folders, but I can imagine someone might not always be so lucky!

    My best guess is that even though they were separate processes working on separate folders, perhaps there was some shared memory or library that was being used in some way that wasn't anticipating more than one process reading/writing to it.

    To make sure this wasn't some fluke disaster, and also that my computer was capable of doing it correctly, I tried running it again on two sets of temporary files, and the result was pretty much the same (corrupted files, and files appearing in the wrong directory). I then ran it with only one set of files being processed, and it concluded perfectly, with no corruption or craziness.

    Also, I was able to get the same result not even using batch jobs. By having two instances of Irfanview open, forcing it to rotate two different images 90 degrees, and being quick enough to make them both start about the same time, the resulting files were corrupted.

    And finally, even though this is probably already too much information, here is a shot of the aftermath.

    It seems like I am probably the only idiot who would try to do this, but I figure I should post about it, just in case! Perhaps it can at least be a warning to others to not do what I did.

    #2
    EDIT:

    You are right. I just reproduced the problem by simultanously ordering 2 instances to rotate JPEGs in 2 separate folders. OMG!!!! Thank you very much for reporting this problem.


    I recently found out that I can apply lossless JPEG operations to large numbers of files at once, through selecting them in the thumbnail viewer. I noticed that it seems like even if you select all the images in a folder, it only will actually apply the operation to the ones whose thumbnails have been generated already
    A while ago I have reported (on the old forum) that while doing lossless transformations on a Win98 system IrfanView 3.98 will allocate an increasing ammount of memory and abort processing JPEGs when there was no memory available. I think I might have been wrong back then. IV really doesn't do processing on files without generated thumbnails, like Kavendek says.

    What is reproducable (I hope): IrfanView will not start processing a single file when there is not enough memory available, but won't warn about it. Perhaps you should say how many megabytes are needed to see if the operation is possible on the given computer.
    Last edited by j7n; 15.06.2007, 09:24 AM. Reason: Testing done

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