Provided by: dvbackup_0.0.4-9_amd64 bug


       dvbackup — Converter from arbitrary data to a DV stream


       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]


       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

                 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

                 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!


       This manual page was written by Robert Jordens 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.