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Filter_text Documentation

Capabilities

Video Audio RGB YUV YUV422 multiple instances processing type
yes no yes yes no no POST

Introduction

This filter allows you to render arbitrary text into the video stream It uses libfreetype2 to render the font so it can handle all fonts libfreetype can handle.

You need libfreetype2 installed and enabled during configure time to make use of this filter.

Parameters

As usual, the default setting should get you going, still there a tons of options to play with.

Default values are shown in [green] in square brackets.

string text to print [date]
This is probably the most important option you want to change. It is the text which will be rendered into the video. If the string is not specified, the filter will render the current time and date.

dpi dots-per-inch resolution [96]
The dots-per-inch resolution of the rendered letters.

points point size of font in 1/64 [25]
The point size of the rendered letters.

font full path to font file [/usr/X11R6/.../arial.ttf]
Specifies which font file to use. You must supply the full path to the file. Default is /usr/X11R6/lib/X11/fonts/TrueType/arial.ttf

fade Fade in and/or fade out (0=off, 1=slow, 10=fast)[0]
turns on a smooth fadein and fadeout. As higher the argument is, the faster the text will be blended. If you specify a range for the filter to apply, the fadein will start at the beginning of the range and fadeout will be finished at the end of the range. See below for an ascii art.

notransparent disable transparency
Default is to enable transparency. Sometimes the text is unreadable especially on bright background so you may wish to disable it. The text will be drawn in a black box.

pos Position (0-width x 0-height) [0x0]
Position of the text (in pixels) The "origin" of the text is the upper left corner of the bounding box.

posdef Position (0=None, 1=TopL 2=TopR 3=BotL 4=BotR 5=Cent 6=BotCent) [0]
Predefined Position.
1: Top Left
2: Top Right
3: Bottom Left
4: Bottom Right
5: Center
6: Center Bottom

range apply filter to [start-end]/step frames [0-oo/1]
defines a frame range in which the image should appear in the video

range together with fade
Say you want the text to be visible from frame 50 until frame 250 and you also want a slow fade (e.g. 2). The number of frames the fade will take is 100/2 = 50 frames, so
     0        50         100         150        200        250
     |---------|----------|-----------|----------|----------|------> Frames
            fadein      full                  fadeout   invisible
             start    visible                  start

Usage Examples

 $ transcode [...] -J text=string="Hello World":fade=2:range=50-250

 $ transcode [...] -J text=string="Hello World":posdef=5

 $ transcode [...] -J text=string="Hello World":posdef=5:points=30

 -J text=string="Hello World":posdef=6:notransparent:fade=7:range=50-250

Limitations


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Edited December 25, 2004 11:59 pm by Monroe (diff)
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