AssRender is an AviSynth plugin that renders ASS/SSA and SRT (without the
HTML-like markup) subtitles. It uses libass to render the subtitles, which makes
it the fastest and most correct ASS renderer for AviSynth.

This also means that it is much more picky about script syntax than VSFilter
and friends, so keep that in mind before blaming the filter. Yes, people have
reported a lot of errors that were actually the script author’s fault.

Usage:
assrender(clip, string file, [string vfr, int hinting, float scale,
        float line_spacing, float dar, float sar, int top, int bottom, int left,
        int right, string charset, int debuglevel, string fontdir,
        string srt_font, string colorspace])

string file:
    Your subtitle file. May be ASS, SSA or SRT.
string vfr:
    Specify timecodes v1 or v2 file when working with VFRaC.
int hinting:
    Font hinting mode. Choose between 
    none (0, default), light (1), normal (2) and Freetype native (3) autohinting.
float scale:
    Font scale. Defaults to 1.0.
float line_spacing:
    Line spacing in pixels. Defaults to 1.0 and won’t be scaled with frame size.
float dar, float sar:
    Aspect ratio. Of course you need to set both parameters.
int top, int bottom, int left, int right:
    Margins. They will be added to the frame size and may be negative.
string charset:
    Character set to use, in GNU iconv or enca format. Defaults to UTF-8.
    Example enca format: enca:pl:cp1250
        (guess the encoding for Polish, fall back on cp1250)
int debuglevel:
    How much crap assrender is supposed to spam to stderr.
string fontdir:
    Additional font directory.
    Useful if you are lazy but want to keep your system fonts clean.
string srt_font:
    Font to use for SRT subtitles.
    Defaults to whatever Fontconfig chooses for “sans-serif”.
string colorspace:
    The color space of your (YUV) video. Possible values:
        - Rec2020, BT.2020
        - Rec709, BT.709
        - Rec601, BT.601
    Default is to use the ASS script’s “Video Colorspace” property, else guess
    based on video resolution (width > 1920 or height > 1080 → BT.2020,
    then width > 1280 or height > 576 → BT.709).