captionbob.effects.fade_in

Fade in effect: a caption shows whole and fades in.

A caption shows a few words. All its words show together from the time at which the first word is spoken. The caption starts transparent and gets its full color in the fade time, along the curve that the easing names. The caption leaves with no fade.

The effect draws nothing itself. It builds the text of an ASS script, and the ffmpeg filter ass draws the script on the video. The common part of the effects is in effect_common.py.

Source file: captionbob/effects/fade_in.py

Settings

The command line and the HTTP API call this effect the style fade_in. Its settings class is FadeInSettings. Each setting has the default below.

Setting	Type	Default	Description
most_words	integer	3	The most words that one caption shows.
fewest_words	integer	1	The fewest words that one caption shows, when its sentence is long enough for that.
font_name	string	"DejaVu Sans"	Name of the font of the text.
font_size	integer	80	Height of the font in pixels.
bold	boolean	true	True for bold text.
primary_color	string	"#FFFFFF"	Color of the text, as "#RRGGBB".
stroke_color	string	"#000000"	Color of the outline of the text, as "#RRGGBB".
stroke_width	number	6.0	Width of the outline in pixels. 0 gives no outline.
bottom_position	number	0.75	Where the bottom of the caption sits, as a part of the video height from the top. 0.75 is three quarters of the way down.
side_margin	integer	54	Room in pixels that stays free on the left and on the right of the caption. A caption that is too wide for the room between the margins breaks into lines.
fade_seconds	number	0.5	Time in which a caption fades in. 0 shows the caption at once. A caption that leaves before the end of this time does not get its full color.
easing	string	"ease-out"	Name of the curve of the fade: "linear", "ease-in", "ease-out" or "ease-in-out".
hold_seconds	number	0.6	The longest time that a caption stays after its last word ends. The caption goes earlier when the next caption starts.

FadeInSettings

@dataclass(frozen=True)
class FadeInSettings(CaptionSettings)

The look and the timing of the fade in effect.

The settings of CaptionSettings come first: the word counts, the font, the colors, the stroke, the bottom position and the side margin. These settings follow them.

Args:

• fade_seconds: Time in which a caption fades in. 0 shows the caption at once. A caption that leaves before the end of this time does not get its full color.
• easing: Name of the curve of the fade: "linear", "ease-in", "ease-out" or "ease-in-out".
• hold_seconds: The longest time that a caption stays after its last word ends. The caption goes earlier when the next caption starts.

Raises:

• TypeError: When a word count is not a whole number.
• ValueError: When a value is outside its range, when a color is not in the form "#RRGGBB", when the font name is empty or holds a comma, or when the easing is not one of the four names.

FadeInEffect

class FadeInEffect
    def __init__(self, settings: FadeInSettings) -> None

Builds the ASS script that fades each caption in.

Args:

• settings: The look and the timing of the effect.

FadeInEffect.build_ass_text

def build_ass_text(self, words: Sequence[Word], video: VideoInfo) -> str

Build the ASS script of the effect for the words of one video.

Each caption group is one event of the script. An event starts with its first word, and all its words show from that time. It ends when the next caption starts, and at the latest the hold time after its last word and at the end of the video.

Args:

• words: The words of the video in time order, each with its times.
• video: The frame size and the duration of the video.

Returns:

The text of the ASS script. It has no event when there are no words.

Raises:

• ValueError: When the side margins leave no room for the caption in the width of the video.