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fix: scale image subtitles using dedicated filter #175

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Merged
jasongdove merged 1 commit into from
Jul 9, 2026
Merged

fix: scale image subtitles using dedicated filter #175

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19 changes: 5 additions & 14 deletions crates/ffpipeline/src/pipeline.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,8 +26,8 @@ use crate::video_codec::VideoCodec;
use crate::video_decoder::VideoDecoder;
use crate::video_filter::{
ColorChannelMixerFilter, CropFilter, DeinterlaceFilter, FadeFilter, FormatFilter, LoopFilter,
PadFilter, ScaleFilter, SoftwareDeinterlaceFilter, SoftwareDeinterlaceOptions, SubtitlesFilter,
ToneMapFilter, VideoFilter,
PadFilter, ScaleFilter, SoftwareDeinterlaceFilter, SoftwareDeinterlaceOptions,
SubtitleImageScaleFilter, SubtitlesFilter, ToneMapFilter, VideoFilter,
};

pub const KEYFRAME_INTERVAL_SECONDS: u32 = 2;
Expand Down Expand Up @@ -447,8 +447,7 @@ impl Pipeline {
&& let Some(subtitle_input) = input_settings.subtitle_input.as_ref()
{
if subtitle_stream.is_subtitle_image()
&& let Some(height) = subtitle_stream.height
&& let Some(width) = subtitle_stream.width
&& let Some(size) = final_output_settings.video_size
{
inputs.push(PipelineInput::Subtitle {
input_source: subtitle_input.input_source.to_owned(),
Expand All @@ -458,7 +457,7 @@ impl Pipeline {
});

let secondary_initial_state = FrameState {
size: FrameSize { width, height },
size,
is_anamorphic: subtitle_stream.is_anamorphic(),
is_interlaced: false,
sample_aspect_ratio: subtitle_stream.sample_aspect_ratio.to_owned(),
Expand All @@ -474,15 +473,7 @@ impl Pipeline {

filters.push(PipelineFilter::Overlay(OverlayFilter {
kind: SoftwareOverlay::default().into(),
secondary: vec![
ScaleFilter {
size: final_output_settings.video_size,
scaling_mode: ScalingMode::ScaleAndPad,
input_is_anamorphic: subtitle_stream.is_anamorphic(),
force_original_aspect_ratio: None,
}
.into(),
],
secondary: vec![SubtitleImageScaleFilter { size }.into()],
secondary_initial_state,
secondary_source: OverlaySource::Subtitle,
location: None,
Expand Down
31 changes: 31 additions & 0 deletions crates/ffpipeline/src/video_filter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,7 @@ pub enum VideoFilter {
Deinterlace(DeinterlaceFilter),
HwMap(HwMapFilter),
Subtitles(SubtitlesFilter),
SubtitleImageScale(SubtitleImageScaleFilter),
ColorChannelMixer(ColorChannelMixerFilter),
Fade(FadeFilter),
Crop(CropFilter),
Expand Down Expand Up @@ -524,6 +525,36 @@ impl VideoFilterOp for SubtitlesFilter {
}
}

#[derive(Debug, Clone)]
pub struct SubtitleImageScaleFilter {
pub size: FrameSize,
}

impl VideoFilterOp for SubtitleImageScaleFilter {
fn evaluate(&self, _state: &FrameState, _info: &FfmpegInfo) -> Option<VideoFilter> {
Some(self.clone().into())
}

fn apply_to(&self, state: &mut FrameState) {
state.size = self.size;
state.is_anamorphic = false;
state.sample_aspect_ratio = Some(String::from("1:1"));
state.display_aspect_ratio = None;
state.surface = FrameSurface::System;
}

fn required_surface(&self) -> Option<FrameSurface> {
Some(FrameSurface::System)
}

fn as_arg(&self) -> Option<String> {
Some(format!(
"scale={}:{}:flags=fast_bilinear:force_original_aspect_ratio=decrease,setsar=1",
self.size.width, self.size.height,
))
}
}

#[derive(Debug, Clone)]
pub struct ColorChannelMixerFilter {
pub alpha: f32,
Expand Down