av-denoise 0.4.0-alpha5

Fast, best in class video denoising for all providing NLMeans, NLMeans-HQ and NL4D algorithms.
Documentation 
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use av_denoise::{Depth, Subsampling};

/// Maps our [`Subsampling`] and [`Depth`] onto the [`y4m::Colorspace`]
/// used to read the input and write the output header.
pub fn subsampling_to_y4m(s: Subsampling, depth: Depth) -> y4m::Colorspace {
    match (s, depth) {
        (Subsampling::Yuv420, Depth::Eight) => y4m::Colorspace::C420,
        (Subsampling::Yuv420, Depth::Ten) => y4m::Colorspace::C420p10,
        (Subsampling::Yuv420, Depth::Twelve) => y4m::Colorspace::C420p12,
        (Subsampling::Yuv422, Depth::Eight) => y4m::Colorspace::C422,
        (Subsampling::Yuv422, Depth::Ten) => y4m::Colorspace::C422p10,
        (Subsampling::Yuv422, Depth::Twelve) => y4m::Colorspace::C422p12,
        (Subsampling::Yuv444, Depth::Eight) => y4m::Colorspace::C444,
        (Subsampling::Yuv444, Depth::Ten) => y4m::Colorspace::C444p10,
        (Subsampling::Yuv444, Depth::Twelve) => y4m::Colorspace::C444p12,
    }
}

/// Maps a [`y4m::Colorspace`] back onto our [`Subsampling`] and
/// [`Depth`].
///
/// Grayscale and any other unsupported colorspace are rejected with an
/// error naming what is required instead.
pub fn subsampling_from_y4m(c: y4m::Colorspace) -> Result<(Subsampling, Depth), anyhow::Error> {
    let sub = match c {
        y4m::Colorspace::C420
        | y4m::Colorspace::C420jpeg
        | y4m::Colorspace::C420paldv
        | y4m::Colorspace::C420mpeg2
        | y4m::Colorspace::C420p10
        | y4m::Colorspace::C420p12 => Subsampling::Yuv420,
        y4m::Colorspace::C422 | y4m::Colorspace::C422p10 | y4m::Colorspace::C422p12 => Subsampling::Yuv422,
        y4m::Colorspace::C444 | y4m::Colorspace::C444p10 | y4m::Colorspace::C444p12 => Subsampling::Yuv444,
        other => anyhow::bail!("unsupported y4m colorspace {other:?}, need 4:2:0, 4:2:2, or 4:4:4"),
    };

    let depth = Depth::from_bits(c.get_bit_depth())?;

    Ok((sub, depth))
}

/// Pulls the `X`-prefixed vendor extension params out of a decoded y4m
/// header's raw params bytes, `XCOLORRANGE=LIMITED` being the common one.
///
/// The leading `X` is stripped so the result can go straight to
/// [`y4m::EncoderBuilder::append_vendor_extension`], which adds the `X`
/// back when it writes the output header.
///
/// This is how whatever colorspace and range tags the source declared
/// reach the output instead of being dropped.
///
/// A token that [`y4m::VendorExtensionString`] rejects, which means one
/// containing a space, is skipped rather than failing the run.
pub fn y4m_vendor_extensions(raw_params: &[u8]) -> Vec<y4m::VendorExtensionString> {
    raw_params
        .split(|&b| b == b' ')
        .filter(|tok| tok.first() == Some(&b'X'))
        .filter_map(|tok| y4m::VendorExtensionString::new(tok[1..].to_vec()).ok())
        .collect()
}

#[cfg(test)]
mod colorspace_tests {
    use super::*;

    #[test]
    fn colorspace_round_trips_every_supported_combination() {
        let combos = [
            (Subsampling::Yuv420, Depth::Eight),
            (Subsampling::Yuv420, Depth::Ten),
            (Subsampling::Yuv420, Depth::Twelve),
            (Subsampling::Yuv422, Depth::Eight),
            (Subsampling::Yuv422, Depth::Ten),
            (Subsampling::Yuv422, Depth::Twelve),
            (Subsampling::Yuv444, Depth::Eight),
            (Subsampling::Yuv444, Depth::Ten),
            (Subsampling::Yuv444, Depth::Twelve),
        ];

        for (sub, depth) in combos {
            let cs = subsampling_to_y4m(sub, depth);
            let (rsub, rdepth) = subsampling_from_y4m(cs).expect("should map back");

            assert_eq!(rsub, sub, "subsampling lost for {cs:?}");
            assert_eq!(rdepth, depth, "depth lost for {cs:?}");
        }
    }

    #[test]
    fn ten_bit_420_maps_to_c420p10() {
        // `y4m::Colorspace` derives only `Debug, Clone, Copy`, not
        // `PartialEq`, so `assert_eq!` won't compile here.
        assert!(matches!(
            subsampling_to_y4m(Subsampling::Yuv420, Depth::Ten),
            y4m::Colorspace::C420p10
        ));
    }

    #[test]
    fn eight_bit_420_variants_all_map_to_yuv420_eight() {
        for cs in [
            y4m::Colorspace::C420,
            y4m::Colorspace::C420jpeg,
            y4m::Colorspace::C420paldv,
            y4m::Colorspace::C420mpeg2,
        ] {
            let (sub, depth) = subsampling_from_y4m(cs).expect("should map");
            assert_eq!(sub, Subsampling::Yuv420);
            assert_eq!(depth, Depth::Eight);
        }
    }

    #[test]
    fn grayscale_colorspaces_are_rejected_with_a_clear_message() {
        for cs in [y4m::Colorspace::Cmono, y4m::Colorspace::Cmono12] {
            let err = subsampling_from_y4m(cs).expect_err("grayscale should be rejected");
            let msg = err.to_string();
            assert!(
                msg.contains(&format!("{cs:?}")),
                "error should name the offending colorspace, got {msg}"
            );
        }
    }
}