NAME

       dvbackup — Converter from arbitrary data to a DV stream

SYNOPSIS

       dvbackup   [--version]   [-n|--ntsc-mode]   [-d|--decode]   [-t|--verify]   [-b|--set-backup-title=TITLE]
       [--set-picture=PPM-FILE]  [-v|--verbose]  [-p|--prefix=COUNT]  [--test=COUNT]  [-r|--recover]  [--enable-
       audio]  [-?|--help]  [--usage]

DESCRIPTION

       This manual page documents briefly the dvbackup tool.

       This manual page was written for the Debian distribution because the original program  does  not  have  a
       manual page.

       As  you  probably  know, current digital camcorders can save approximately 13 GB of data on those tiny DV
       cartridges at a speed of 3.6 MB/second. That's fast. Very fast. It's faster than most DAT streamers which
       only work at 1 MB/sec or less. We can not use all of the data, but  10  GB  should  be  good  enough  for
       everyone.

       That's  nice, but how can we use this to save data on it? And here comes the fun part: If you read the DV
       documentation carefully, you will notice that the AC DCT coefficients  of  the  video  data  blocks  (8x8
       pixels  in  size) get a fixed amount of space in the DV data stream, but can be terminated earlier with a
       certain code sequence. So let's have some fun: We terminate the AC coefficients immediately leaving  only
       the  DC  coefficient  for  a  fancy  penguin  picture  and  use  the  rest  for  our  backup data. Future
       implementations could easily add a little picture showing the currently written file  or  something  like
       that.

       Then  there  is  the  audio  data,  which  is written uncompressed onto the tape. That means: We tell the
       camcorder at the beginning of each frame, that we won't use audio at all but fill the space reserved  for
       it  with  data. Easy, but somewhat hacky. In fact, I don't know, if this works on every camcorder and not
       only on mine (a Sony VX700). Your mileage may vary.

       To finally bring the data on tape, you have to use an additional  utility,  called  dvconnect,  which  is
       (hopefully  soon)  included into libdv. Take a look at the patch manager if it's not in already. And then
       it's time to rock and roll:

       Advantages of dvbackup over other backup technologies

                 relatively cheap (the cheapest camcorder will be enough, but if you have already one...)

                 the tapes are quite cheap

                 open standard: if your streamer, aah camcorder dies you can rescue your data with any other one
                 (except PAL/NTSC need to fit), you are not bound to a special company

                 it's faster than many streamers and it will be more comfortable - you can use the  search-index
                 function to "jump" to a recording

                 tapes (re)wind faster than many streamers

                 you do not need to rewind the tape to eject it

       Disadvantages of dvbackup

                 you do not get any warranty :-)

       Usage of the Unix client

                 Press  record  on  your  camcorder. (Or use your favorite avc control program for this. For the
                 VX700 this doesn't work and you have to hack  something  together,  that  uses  LANC.  I  might
                 publish my "solution" for this soon...)

                 Type  "find  . |cpio -o -H crc |dvbackup --prefix=125 |dvconnect -s" to stream directly to your
                 camcorder. This most likely does only work on very fast harddisks and  filesystems.  You  might
                 try  something  like  "find  .  |cpio  -o  -H  crc |dvbackup --prefix=125 |dvconnect -s -b 500"
                 Alternatively, you can write the data in several parts on tape. Just go experimenting, and mail
                 me the resulting backup scripts...

                 Stop your camcorder and rewind.

                 Now it's time to verify: Press play on tape ;-)

                 Type "dvconnect |dvbackup -t" and watch for crc errors. The data corruption bug  mentioned  for
                 version  0.0.1  seems  to be fixed so there is no excuse in not using this little nifty program
                 ;-)

                 If you want to restore: Do a simple "dvconnect |dvbackup -d|cpio -imV". CPIO will also  happily
                 tell  you  about CRC errors. So you might want to check using cpio's archive test mode too. But
                 keep in mind, that cpio's CRC function is not that fast!

AUTHOR

       This manual page was written by Robert Jordens jordens@debian.org for the Debian system (but may be  used
       by others).  Permission is granted to copy, distribute and/or modify this document under the terms of the
       GNU  General  Public License, Version 2. On Debian systems, the full text of this license can be found in
       the file /usr/share/common-licenses/GPL-2.

                                                                                                     DVBACKUP(1)