Skip to content

RGB to YUV Performance Improvements #81

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
ralfbiedert merged 1 commit into from
Sep 5, 2025
+15 −34
Merged

RGB to YUV Performance Improvements #81

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
49 changes: 15 additions & 34 deletions openh264/src/formats/rgb2yuv.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -58,46 +58,27 @@ pub fn write_yuv_scalar(rgb: impl RGB8Source, dimensions: (usize, usize), y_buf:

let dimensions_padded = rgb.dimensions_padded();
let width = dimensions.0;
let height = dimensions.1;

let half_width = width / 2;
let rgb8_data = rgb.rgb8_data();

// y is full size, u, v is quarter size
let mut write_y = |x: usize, y: usize, rgb: &[u8]| {
let (r, g, b) = (f32::from(rgb[0]), f32::from(rgb[1]), f32::from(rgb[2]));
y_buf[x + y * width] = (0.09765625f32.mul_add(b, 0.2578125f32.mul_add(r, 0.50390625 * g)) + 16.0) as u8;
};

let mut write_u = |x: usize, y: usize, rgb: &[u8]| {
let (r, g, b) = (f32::from(rgb[0]), f32::from(rgb[1]), f32::from(rgb[2]));
u_buf[x + y * half_width] = (0.4375f32.mul_add(b, (-0.1484375f32).mul_add(r, -0.2890625 * g)) + 128.0) as u8;
};
for (pix, y) in rgb8_data.chunks_exact(3).zip(y_buf.iter_mut()) {
*y = (((66 * u32::from(pix[0]) + 129 * u32::from(pix[1]) + 25 * u32::from(pix[2])) >> 8) + 16) as u8;
}

let mut write_v = |x: usize, y: usize, rgb: &[u8]| {
let (r, g, b) = (f32::from(rgb[0]), f32::from(rgb[1]), f32::from(rgb[2]));
v_buf[x + y * half_width] = ((-0.0703125f32).mul_add(b, 0.4375f32.mul_add(r, -0.3671875 * g)) + 128.0) as u8;
};
let r1 = rgb8_data.chunks_exact(dimensions_padded.0 * 3).step_by(2);
let r2 = rgb8_data.chunks_exact(dimensions_padded.0 * 3).skip(1).step_by(2);

for i in 0..width / 2 {
for j in 0..height / 2 {
let px = i * 2;
let py = j * 2;
let pix0x0 = &rgb8_data[(px + py * dimensions_padded.0) * 3..][..3];
let pix0x1 = &rgb8_data[(px + (py + 1) * dimensions_padded.0) * 3..][..3];
let pix1x0 = &rgb8_data[(px + 1 + (py) * dimensions_padded.0) * 3..][..3];
let pix1x1 = &rgb8_data[(px + 1 + (py + 1) * dimensions_padded.0) * 3..][..3];
let avg_pix = [
((u32::from(pix0x0[0]) + u32::from(pix0x1[0]) + u32::from(pix1x0[0]) + u32::from(pix1x1[0])) / 4) as u8,
((u32::from(pix0x0[1]) + u32::from(pix0x1[1]) + u32::from(pix1x0[1]) + u32::from(pix1x1[1])) / 4) as u8,
((u32::from(pix0x0[2]) + u32::from(pix0x1[2]) + u32::from(pix1x0[2]) + u32::from(pix1x1[2])) / 4) as u8,
];
let u_rows = u_buf.chunks_exact_mut(half_width);
let v_rows = v_buf.chunks_exact_mut(half_width);
for (((r1, r2), u), v) in r1.zip(r2).zip(u_rows).zip(v_rows) {
for (((pix0, pix1), u), v) in r1.chunks_exact(2 * 3).zip(r2.chunks_exact(2 * 3)).zip(u).zip(v) {
let r = (i16::from(pix0[0]) + i16::from(pix0[3]) + i16::from(pix1[0]) + i16::from(pix1[3]) + 2) / 4;
let g = (i16::from(pix0[1]) + i16::from(pix0[4]) + i16::from(pix1[1]) + i16::from(pix1[4]) + 2) / 4;
let b = (i16::from(pix0[2]) + i16::from(pix0[5]) + i16::from(pix1[2]) + i16::from(pix1[5]) + 2) / 4;

write_y(px, py, pix0x0);
write_y(px, py + 1, pix0x1);
write_y(px + 1, py, pix1x0);
write_y(px + 1, py + 1, pix1x1);
write_u(i, j, &avg_pix);
write_v(i, j, &avg_pix);
*u = (((-38 * r + 112 * b - 74 * g) >> 8) + 128) as u8;
*v = (((112 * r - 18 * b - 94 * g) >> 8) + 128) as u8;
}
}
}
Expand Down
Loading