Hi,						Menden, 09 Oct 99

    This program decodes and displays Videotext/Teletext from a
    /dev/vbi device.


A WARNING first:

    The bttv-driver is buggy.  Don't try to run alevt together
    with anything that grabs video data from /dev/video.
    The grabber will stop running, and some time later the
    kernel will crash due to an out of memory condition.

    It seems to work with programs that just use video overlay,
    for example xawtv in overlay mode.

    UPDATE: I've seen memory corruptions, too :-(


COMPILE & INSTALL:

    There's nothing to configure.  A simple 'make' is all.
    If you do not want png support remove the WITH_PNG in
    the Makefile.

    It gives you 'alevt', 'alevt-date', and 'alevt-cap' and
    their man pages 'alevt.1x', 'alevt-date.1', and 'alevt-cap.1'.

    You can install it where ever you want (i.e. /usr/local/bin).
    The programs are selfcontained and require no other files.

    NOTE: Be careful with 'make install'.  It's just for me :-)


OLDER BTTV (or 2.2.x kernel versions):

    If you have an bttv driver < v0.5.20 or the one contained in
    the 2.2.x kernels you should supply the -oldbttv option.


TOP-Text:
    I can't find any online documentation about TOP-Text :-(
    If you know an URL, please drop me a note.

    Hmm... found something in c't 09/92... How complicated...
    Could have been designed by GNU-folks *g*.  FastText is much
    cleaner.
    (Thanks to Guenther Montag for the pointer.)

    I'm still interested in an URL of a more formal specification.


PROBLEMS:

    If you have a lot of decoding errors (lot of these lightning symbols)
    you may try pressing the 'f' and 'F' key.  This allows fine tuning of
    the decoder circuit.  There's also a -finetune command line option.
    This should only be necessary on really bad signals.

    Maybe, I add autotuning later...

    UPDATE: added autotuning.  It's the default.  If you add -debug the
    the actions of the pll are printed to stdout.

    To get the old (pre finetune) behaviour start it with -finetune 0.


ALEVT-DATE:
    I added a little tool to set the system time from the videotext
    time.  The date is not interpreted (not even transmitted on some
    channels).  So it allows only adjustment of +/-12 hours.
    The default allowed adjustment is limited to +/-2 hours (use
    -delta to change).  Without the -set option it just display
    the date in the format of the date command.  Look at strftime(3)
    for possible control sequences you may use in the -format option.


HACKING:

    If you want to play with the font size, you may resize it with
    xv (xv font.xbm).  Just make sure, that its width is a multiple of
    32 and its height a multiple of 8.  A simple make will create
    a version of AleTV with the new font.  Warning: a make clean
    will erase font.xbm.  The next make will recreate font.xbm from
    vtxt.bdf.

    AleVT has a build in page editor.  If you start it with -editor
    you may press 'e' to invoke it.  For the usage you have to consulte
    the sources.  (It's very crude!)


TODO: (no specific order)

    - Better looking font (12x16 seems the right size).
    - Separated graphics.


NEWER VERSIONS:

    The primary site of AleVT is http://user.exit.de/froese
    Also uploaded to ftp://metalab.unc.edu/pub/Linux/apps/video


Have fun,

Edgar Toernig (froese@gmx.de)
