Function create_encoder_with_scale 

pub fn create_encoder_with_scale(
    output_path: &Path,
    src_width: u32,
    src_height: u32,
    dst_width: u32,
    dst_height: u32,
    fps: f64,
) -> Result<Box<dyn VideoEncoder>, VideoError>

Create an MP4 encoder with FFmpeg native nearest-neighbor scaling.

This passes scaling to FFmpeg using -vf scale=W:H:flags=neighbor, which is efficient and produces sharp pixel edges.