Module convert 

Normalization of decoded frames into the virtual device’s fixed format.

The device is a fixed-function camera: one raw pixel format at one size. Whatever the client camera delivers (any size, full- or limited-range luma) is fitted into that: the frame is scaled to fit with black bars when its size differs, full-range (JPEG) samples are compressed into the limited range every V4L2 consumer assumes, and the planes are emitted as I420, NV12, or YUYV. The common path — a frame already at the device size, limited range, I420 device — is a plain plane copy straight into the ring slot.

Structs

DeviceFormat

Target geometry: the device format the ring advertises.

I420Buffer

Owned, tightly packed I420 buffer used as the normalization scratch.

I420View

Borrowed I420 planes with arbitrary strides.

Normalizer

Scratch state kept across frames so normalization allocates only on geometry changes.

Orientation

One upright transform: clockwise quarter turns, then a horizontal mirror.

RangeLut 🔒

Full-range to limited-range lookup tables (BT.601/709 quantization; the matrix is unchanged).

Constants

ORIENT_TILE 🔒

Destination square a quarter turn is taken in, so the source rows it gathers from stay in the innermost cache across the whole square.

Functions

bilinear_plane 🔒

Separable bilinear resample of one plane (fixed point 16.16).

copy_plane 🔒

Copy a plane row by row, optionally through a range LUT.

emit 🔒

Emit src (already at the device size) as the device fourcc.

fit

Largest even-aligned size of sw x sh that fits into dw x dh preserving aspect, and the even-aligned offsets that center it.

halve_plane 🔒

Average 2x2 blocks: exact halving, used before bilinear when the ratio exceeds 2 so strong downscales do not alias.

orient_i420

Apply o to src, producing a tightly packed upright copy in out. The chroma planes of the rotated picture are exactly the rotated chroma planes (odd-turn chroma dimensions transpose with them), so each plane is oriented independently.

orient_plane 🔒

Rotate one plane clockwise into a tightly packed destination (whose width is h for odd turn counts), mirroring each destination row for hflip.

range_lut 🔒

range_luts 🔒

The LUTs that move src samples into the device’s range: full-range JPEG into a limited-range raw device, limited-range video into the full-range MJPEG device, or nothing when the two agree.

scale_plane 🔒

Resample a plane into dst (tightly packed dw x dh), halving first while the source is more than twice the destination in either dimension.

yuyv_scalar 🔒