VapourSynth 1.0 documentation
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# VapourSynth C API Reference

See the example filters in the sdk dir. Reading simplefilters.c, which contains almost all built-in functions, can also be very helpful.

## Public Headers

- VapourSynth.h

## Reserved Frame Properties

All frames contain a map of key–value pairs. It is recommended that these properties are named using only a-z, A-Z, 0-9 using CamelCase. There is a special category of keys starting with _ which have strictly defined meanings specified below. It is acceptable to not set any of these keys if they are unknown. It is also a fatal error to set them to a value not specified below.

    The frame's absolute timestamp in seconds if reported by the source filter.
    Should only be set by the source filter and not be modified.
    _AbsoluteTime float

    Chroma sample position in YUV formats.
    _ChromaLocation int (0=left, 1=center, 2=topleft, 3=top, 4=bottomleft, 5=bottom)

    Full or limited range (PC/TV range). Primarily used with YUV formats.
    _ColorRange int (0 = full range, 1 = limited range)

    Encoded as in avcodec.h in libavcodec. It's so convoluted I'm not
    going to try to describe it here.
    _ColorSpace int

    Whether or not the frame needs postprocessing, usually hinted from field
    matching filters.
    _Combed bint

    The frame's duration in seconds as a rational number.
    Filters that modify the framerate should also change this value.
    _DurationNum int
    _DurationDen int

    If the frame has been split into fields this says if the frame was
    derived from top or bottom fields.
    _Field int (0 = from bottom field, 1 = from top field)

    If the frame is composed of two independent fields (interlaced).
    _FieldBased int (0 = frame based, 1 = field based)

    A single character describing the frame type. It uses the common
    IPB letters but other letters may also be used for formats with
    additional frame types.
    _PictType data

    Display aspect ratio as a rational number.
    _SARNum int
    _SARDen int

    Indicates a scenechange for the next/previous frame transition.
    _SceneChangeNext bint
    _SceneChangePrev bint