rust_highlight/src/lib.rs

use std::process::Command;
use std::path::Path;

pub fn render_video(
    id: usize,
    image_path: &str,
    audio_path: &str,
    duration: f64,
    words: Vec<(String, (u32, u32, u32, u32))>,
    output_dir: &str,
) -> Result<String, String> {
    // Validate paths
    if !Path::new(image_path).exists() {
        return Err(format!("Image not found: {}", image_path));
    }
    if !Path::new(audio_path).exists() {
        return Err(format!("Audio not found: {}", audio_path));
    }

    let output_path = format!("{}/clip{}.mp4", output_dir, id);
    let duration_str = duration.to_string();
    let n_words = words.len() as f64;
    let highlight_duration = duration / n_words;

    // Build complex filter graph
    let mut filter_complex = String::new();
    let mut last_output = "0:v".to_string();

    for (i, (_, (x, y, w, h))) in words.iter().enumerate() {
        let start = i as f64 * highlight_duration;
        let end = start + highlight_duration;

        // Create highlight box
        filter_complex.push_str(&format!(
            "[{last_out}]drawbox=x={x}:y={y}:w={w}:h={h}:color=yellow@0.5:t=fill:enable='between(t,{start:.3},{end:.3})'[v{i}];",
            last_out = last_output,
            x = x,
            y = y,
            w = w,
            h = h,
            start = start,
            end = end,
            i = i
        ));
        last_output = format!("[v{i}]");
    }

    // Remove trailing semicolon
    filter_complex.pop();

    // FFmpeg command with optimized settings
    let status = Command::new("ffmpeg")
        .args(&[
            "-y", // Overwrite output
            "-hwaccel", "auto", // Enable hardware acceleration
            "-loop", "1",
            "-i", image_path,
            "-i", audio_path,
            "-filter_complex", &filter_complex,
            "-map", &last_output,
            "-map", "1:a",
            "-c:v", "libx264",
            "-preset", "fast", // Balance between speed and compression
            "-crf", "18", // High quality (lower = better quality)
            "-pix_fmt", "yuv420p",
            "-movflags", "+faststart", // For web streaming
            "-c:a", "aac",
            "-b:a", "192k", // Higher audio bitrate
            "-r", "60", // Higher framerate for smoother animation
            "-t", &duration_str,
            "-vsync", "2", // Frame rate conversion method
            &output_path,
        ])
        .status();

    match status {
        Ok(exit_status) if exit_status.success() => Ok(output_path),
        Ok(_) => Err("FFmpeg command failed".to_string()),
        Err(e) => Err(format!("Failed to execute FFmpeg: {}", e)),
    }
}


#[pymodule]
fn rust_highlight(_py: Python, m: &PyModule) -> PyResult<()> {
    m.add_function(wrap_pyfunction!(render_video, m)?)?;
    Ok(())
}