[Ffmpeg-devel] [RFC]: vhook Documentation

[Diego Biurrun]

Here's a review of your patch..

On Tue, Jan 16, 2007 at 09:45:45PM -0800, C.Ren Boca wrote:
> 
> --- hooks.texi 2007-01-17 00:30:30.000000000 -0500
> +++ hooks.texi.new 2007-01-17 00:38:32.000000000 -0500
> @@ -39,63 +39,57 @@
>  
> -You may also overlay an image (even semi-transparent) like TV stations do.
> -You may move either the text or the image around your video to create
> -scrolling credits, for example.
> +Features:
> +- True Type, Type1 and others via FreeType2 library

TrueType

> +- Font kerning (better output)
> +- Line Wrap (if the text doesn't fit, the next char goes to the next line)
> +- Background box (currently in development)
> +- Outline 

Trailing whitespace, please remove that from patches.

Also, why not make this feature list a proper bulletted list with
texinfo markup?

>  Text fonts are being looked for in a FONTPATH environment variable.
>  
>  Options:
>  @multitable @columnfractions .2 .8
> - at item @option{-c <color>}     @tab The color of the text
> - at item @option{-F <fontname>}  @tab The font face and size
> - at item @option{-t <text>}      @tab The text
> - at item @option{-f <filename>}  @tab The filename to read text from
> - at item @option{-x <expresion>} @tab X coordinate of text or image
> - at item @option{-y <expresion>} @tab Y coordinate of text or image
> - at item @option{-i <filename>}  @tab The filename to read a image from
> - at end multitable
> -
> -Expresions are functions of these variables:
> - at multitable @columnfractions .2 .8
> - at item @var{N} @tab frame number (starting at zero)
> - at item @var{H} @tab frame height
> - at item @var{W} @tab frame width
> - at item @var{h} @tab image height
> - at item @var{w} @tab image width
> - at item @var{X} @tab previous x coordinate of text or image
> - at item @var{Y} @tab previous y coordinate of text or image
> + at item @option{-c <color>}          @tab Foreground color of the text ('internet' way) <#RRGGBB> [default #ffffff]
> + at item @option{-C <color>}          @tab Background color of the text ('internet' way) <#RRGGBB> [default #000000]
> + at item @option{-f <font-filename>}  @tab The font file to use
> + at item @option{-o }                 @tab Outline glyphs using the background color
> + at item @option{-t <text>}           @tab The text to display
> + at item @option{-T <filename>}       @tab The filename to read text from
> + at item @option{-x <pos>}            @tab X coordinate of the start of text 
> + at item @option{-y <pos>}            @tab Y coordinate of the start of text 
>  @end multitable
>  
> -You may also use the constants @var{PI}, @var{E}, and the math functions available at the
> -FFmpeg formula evaluator at (@url{ffmpeg-doc.html#SEC13}), except @var{bits2qp(bits)}
> -and @var{qp2bits(qp)}.
> -
> -Usage examples:
> -
> +Usage Example:
>  @example
>     # Remember to set the path to your fonts
> -   FONTPATH="/cygdrive/c/WINDOWS/Fonts/"
> -   FONTPATH="$FONTPATH:/usr/share/imlib2/data/fonts/"
>     FONTPATH="$FONTPATH:/usr/X11R6/lib/X11/fonts/TTF/"
>     export FONTPATH
>  
> -   # Bulb dancing in a Lissajous pattern
> -   ffmpeg -i input.avi -vhook \
> -     'vhook/imlib2.dll -x W*(0.5+0.25*sin(N/47*PI))-w/2 -y H*(0.5+0.50*cos(N/97*PI))-h/2 -i /usr/share/imlib2/data/images/bulb.png' \
> -     -acodec copy -sameq output.avi
> -
> -   # Text scrolling
> -   ffmpeg -i input.avi -vhook \
> -     'vhook/imlib2.dll -c red -F Vera.ttf/20 -x 150+0.5*N -y 70+0.25*N -t Hello' \
> -     -acodec copy -sameq output.avi
> +   # When run from your build location:

I would just assume an installed version of ffmpeg.  Don't bother with
these details.

> +   Will grab video from the first capture card and output it to a MPEG video,

an MPEG

> +   And place  "Weekday-dd/mm/yy-hh:mm:ss" at the top left of the frame, updated every second,
> +   using the Vera Bold TrueType Font, which should exist in: /usr/X11R6/lib/X11/fonts/TTF/   

Ideally, keep lines below 80 characters.

> +   If ffmpeg is installed, it should be in your $PATH, make sure to specify the full path 
> +   of the vhook ".so" file that you are using. 

see above

> +   Check the manpage for strftime() for all the various ways you can format the date and time.

man page

> +Command Line options:
> +-m [0|1]  Mode. Zero is the default Mode, see below.

default mode

> + If mask color is < 0x80 the abs difference is subtracted from the frame. If

absolute

> + This way a mask that is visible both in light pictures and in dark can be

"light pictures and in dark ones" or IMO better "light and dark pictures".

You've removed some parts of the documentation, I'll have to trust that
it's correct since I haven't played around with vhook at all.

Send an updated patch and I'll apply it.

Diego