Struct SubtitleFilterBuilder 

pub struct SubtitleFilterBuilder { /* private fields */ }

Builder for SubtitleFilter; obtain one via SubtitleFilter::builder.

Implementations

impl SubtitleFilterBuilder

pub fn ass_content(self, content: impl Into<String>) -> Self

Uses a complete ASS/SSA script held in memory (UTF-8) — no temp file.

pub fn fonts_dir(self, dir: impl Into<PathBuf>) -> Self

Extra directory scanned for font files (libass fontsdir), typically where application-managed fonts are downloaded to.

pub fn default_font_file(self, font: impl Into<PathBuf>) -> Self

Path to a concrete font file used as the default font. Combined with FontProvider::None this pins rendering to exactly this file and eliminates lookup races between a fonts dir and a family name.

pub fn default_family(self, family: impl Into<String>) -> Self

Family name used when the script’s style does not resolve to a font.

pub fn font_provider(self, provider: FontProvider) -> Self

See FontProvider; defaults to FontProvider::Autodetect.

pub fn force_style(self, style: impl Into<String>) -> Self

Comma-separated Style.Field=Value overrides applied to the script’s style definitions (same semantics as the FFmpeg subtitles filter’s force_style). Inline override tags in dialogue lines still win.

pub fn original_size(self, width: u32, height: u32) -> Self

Resolution the subtitles were authored against, used to compensate the aspect ratio when the video was resized (FFmpeg original_size).

pub fn charenc(self, charenc: impl Into<String>) -> Self

Character encoding of file/SRT sources (FFmpeg charenc; requires the linked FFmpeg to support iconv). Not applicable to Self::ass_content, which must already be UTF-8.

pub fn file(self, path: impl Into<PathBuf>) -> Self

Burns subtitles from a file: .srt/.ass/.vtt, or any container holding a text subtitle stream (same lavformat/lavcodec loader FFmpeg’s subtitles filter uses, including container font attachments).

pub fn srt_content(self, content: impl Into<String>) -> Self

Uses SRT content held in memory (no temp file). Markup supported by FFmpeg’s SRT decoder (<i>, <b>, <font color>, …) is honored.

pub fn stream_index(self, index: usize) -> Self

Selects which subtitle stream to burn when the source has several (0 = first subtitle stream), mirroring FFmpeg’s si option. Only applies to Self::file sources.

pub fn wrap_unicode(self, enable: bool) -> Self

Overrides the automatic Unicode line-wrapping rule (FFmpeg wrap_unicode). Unset = FFmpeg’s auto behavior: enabled for decoded non-ASS sources (SRT/VTT/…), disabled for native ASS scripts. Requires a libass built with libunibreak; otherwise the request is logged and ignored, like FFmpeg.

pub fn shaping(self, shaping: TextShaping) -> Self

Text shaping engine; defaults to TextShaping::Auto (libass’s default, complex shaping), mirroring the FFmpeg ass filter’s shaping option.

pub fn font_scale(self, scale: f64) -> Self

Global multiplier applied to all font sizes (accessibility-style “bigger subtitles” without editing the script). 1.0 = script sizes.

pub fn line_position(self, percent: f64) -> Self

Vertical position of regular (non-explicitly-positioned) events, in percent: 0.0 = author intent (default), 100.0 = top of the frame. Typical “raise subtitles” values are 5–20.

pub fn margins(self, top: i32, bottom: i32, left: i32, right: i32) -> Self

Distances (pixels) from the video rectangle to the frame edges, for content with baked-in letterbox/pillarbox bars: subtitles are then laid out relative to the picture area instead of the full frame. Negative values express pan-and-scan. See also Self::use_margins.

pub fn use_margins(self, enable: bool) -> Self

Allows regular events to be placed on the whole frame (e.g. onto letterbox bars declared via Self::margins) instead of only inside the video rectangle.

pub fn build(self) -> Result<SubtitleFilter, SubtitleError>

Validates the configuration, initializes libass, and loads the subtitle source. All failures surface here, never mid-pipeline.

Trait Implementations

impl Debug for SubtitleFilterBuilder

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for SubtitleFilterBuilder

fn default() -> SubtitleFilterBuilder

Returns the “default value” for a type.