/**
 * Forward 4×4 DCT on residual `src - ref`. `src` and `ref` are byte
 * patches addressed at offsets stepping in 32-byte rows; `srcOff` /
 * `refOff` are the starting offsets. `out[outOff..outOff+16)` receives
 * the 16 quantisable coefficients in raster order (DC at index 0).
 */
export declare function fdct4x4(src: Uint8Array, srcOff: number, ref: Uint8Array, refOff: number, out: Int16Array, outOff: number): void;
/**
 * Y2 (DC-of-each-Y-block) Walsh-Hadamard forward transform. Input is
 * 16 int16 values laid out as the DC coefficients of the 16 luma 4×4
 * blocks of a macroblock; output is 16 transformed coefficients ready
 * for the Y2 block's own quantisation pass. Mirrors libwebp's
 * `FTransformWHT_C`.
 *
 * `inOff` indexes into a Y-block coefficient buffer where every 16th
 * entry is the DC of one 4×4 block — caller arranges this so the
 * function can step by 16 to walk the four DC values per row.
 */
export declare function fwht4x4(inBuf: Int16Array, inOff: number, out: Int16Array, outOff: number): void;