av-scenechange 0.4.1

Estimates frames in a video where a scenecut would be ideal
Documentation 
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use crate::util::*;
use std::io::Read;
use v_frame::frame::Frame;
use v_frame::pixel::ChromaSampling;
use v_frame::pixel::Pixel;

pub(crate) fn get_video_details<R: Read>(dec: &y4m::Decoder<R>) -> VideoDetails {
    let width = dec.get_width();
    let height = dec.get_height();
    let color_space = dec.get_colorspace();
    let bit_depth = color_space.get_bit_depth();
    let (chroma_sampling, chroma_sample_position) = map_y4m_color_space(color_space);
    let framerate = dec.get_framerate();
    let time_base = Rational::new(framerate.den as u64, framerate.num as u64);

    VideoDetails {
        width,
        height,
        bit_depth,
        chroma_sampling,
        chroma_sample_position,
        time_base,
    }
}

fn map_y4m_color_space(color_space: y4m::Colorspace) -> (ChromaSampling, ChromaSamplePosition) {
    use y4m::Colorspace::*;
    use ChromaSamplePosition::*;
    use ChromaSampling::*;
    match color_space {
        Cmono => (Cs400, Unknown),
        C420jpeg | C420paldv => (Cs420, Unknown),
        C420mpeg2 => (Cs420, Vertical),
        C420 | C420p10 | C420p12 => (Cs420, Colocated),
        C422 | C422p10 | C422p12 => (Cs422, Colocated),
        C444 | C444p10 | C444p12 => (Cs444, Colocated),
    }
}

pub(crate) fn read_video_frame<R: Read, T: Pixel>(
    dec: &mut y4m::Decoder<R>,
    cfg: &VideoDetails,
) -> Result<Frame<T>, ()> {
    let bytes = dec.get_bytes_per_sample();
    dec.read_frame()
        .map(|frame| {
            let mut f: Frame<T> =
                Frame::new_with_padding(cfg.width, cfg.height, cfg.chroma_sampling, 0);

            let (chroma_width, _) = cfg
                .chroma_sampling
                .get_chroma_dimensions(cfg.width, cfg.height);

            f.planes[0].copy_from_raw_u8(frame.get_y_plane(), cfg.width * bytes, bytes);
            f.planes[1].copy_from_raw_u8(frame.get_u_plane(), chroma_width * bytes, bytes);
            f.planes[2].copy_from_raw_u8(frame.get_v_plane(), chroma_width * bytes, bytes);
            f
        })
        .map_err(|_| ())
}

#[derive(Debug, Clone, Copy)]
pub(crate) struct VideoDetails {
    pub width: usize,
    pub height: usize,
    pub bit_depth: usize,
    pub chroma_sampling: ChromaSampling,
    pub chroma_sample_position: ChromaSamplePosition,
    pub time_base: Rational,
}

impl Default for VideoDetails {
    fn default() -> Self {
        VideoDetails {
            width: 640,
            height: 480,
            bit_depth: 8,
            chroma_sampling: ChromaSampling::Cs420,
            chroma_sample_position: ChromaSamplePosition::Unknown,
            time_base: Rational { num: 30, den: 1 },
        }
    }
}