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FTP problem with .tif files.

Discussion in 'General Technical Discussion' started by WillyPete, Aug 18, 2009.

  1. WillyPete

    WillyPete

    586
    Jan 22, 2009
    London
    We have a client uploading 5-10mb .tif files for their site.
    They're using filezilla as client software, and we use gene6 FTP server.
    Some images are making it through, but some are getting "chopped".

    The image canvas size is correct, but the image itself does not fill it.
    I've verified their source file is ok by having them use an upload service, from which I downloaded a copy of one of the source files.

    Is there some problem with FTP'ing .tif files that I don't know about?

    These guys (Gastownphoto) warn against using LZW compression in .tif files if you want to FTP to them for processing.
    http://www.gastownphoto.com/FTPFilesUpload.html

    Does this compression format not play well with FTP?
    I thought that .tif files were uncompressed anyway?

    Any ideas?
     
  2. WayneF

    WayneF

    Apr 3, 2006
    Texas
    No problem FTP'ing TIF files. Data is all just bytes. FTP just sends bytes, it does not know or care what kind of file format it is. However, FTP default is to send 7 bit text data bytes (ASCII), therefore FTP Binary mode must be used for most data, binary data like images or program files. With only that one exception, it is never about what kind of file it is. But if any binary data is sent as FTP ASCII mode, there will be 100% file corruption, pure garbage comes out. Most FTP software makes that binary choice automatically and correctly based on file name extension (no handling difference in TIF or JPG, but both would be in the list of binary types).

    If they have any issue about LZW compression in TIF files, it is some concern of their destination print processing software (not able to handle LZW), it is not about FTP to get them there.

    Any "chopped" file damage must be about the ftp process, protocols not being observed properly. One end or the other of this specific FTP process failed to deliver the file correctly (other FTP processes surely work fine, as you demonstrated). It would not matter what type of file it was. TIF Files are simply larger binary files than JPG would be.

    Yes, LZW is a very common lossless compression for TIF files. To be lossless, it compresses less than JPG can do, maybe 15% size reduction instead of 90% size reduction. But... lossless means we get back out the same thing that we put into it.
     
    Last edited by a moderator: Aug 18, 2009
  3. Does FTP 'time out'?
     
  4. WillyPete

    WillyPete

    586
    Jan 22, 2009
    London
    There's two tcpip connections in a session.
    The file transmission doesn't, but I've discovered the FTP server's command connection is set to time out at 5 minutes.

    Although the data connection doesn't theoretically need the command connection once the trasnfer starts, I think the problem comes in when the user reconnects by refreshing the destination file list and the command connection re-engages.

    I'm trying out using a 1 hour timeout on Idle connections (Idle = not browsing through folder structure or requesting file list.)
     
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