nv21c.c

#include <assert.h>
#include <fcntl.h>
#include <string.h>
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>

#define w 1920
#define h 1080

static unsigned char yuv[3133440];
static unsigned char rgb[w*h*4];

__attribute__((unused)) static int clamp(int v) {
    if (v < 0) return 0;
    if (v > 255) return 255;
    return v;
}

static uint64_t offs = 0;
static void read8(unsigned char out[8]) {
    /* aml is weird -- every 8 bytes is reversed */
    int n = 8;
    assert(offs < sizeof(yuv));
    while (n--) { out[n] = yuv[offs++]; }
}

#define rgbat(ay, ax) ((w*(ay)+(ax))*4)

int main(int argc, char *argv[]) {
    FILE *fd;

    fd = fopen(argv[1], "r");
    fread(yuv, 1, sizeof(yuv), fd);
    fclose(fd);

    int y, x, dy, dx, si;

    /* do y samples first */
    int bs = 32;
    for (y = 0; y < h; y += bs) {
        for (x = 0; x < w; x += bs) {
            for (dy = 0; dy < bs; dy++) {
                for (dx = 0; dx < bs; dx += 8) {
                    unsigned char lp[8];
                    read8(lp);
                    for (si = 0; si < 8; si++) {
                        int px = rgbat(y+dy, x+dx+si);
                        int y = clamp((lp[si]-12) * 1.16);
                        rgb[px+0] = y;
                        rgb[px+1] = y;
                        rgb[px+2] = y;
                        rgb[px+3] = 255;
                    }
                }
            }
        }
    }

    /* now add in uv samples */
    for (y = 0; y < h; y += 64) {
        for (x = 0; x < w; x += 32) {
            int dx, dy, si;

            for (dy = 0; dy < 64; dy += 2) {
                for (dx = 0; dx < 32; dx += 8) {
                    unsigned char lp[8];
                    read8(lp);

                    for (si = 0; si < 8;) {
                        int u = ((lp[si++]-128) * 1.1);
                        int v = ((lp[si++]-128) * 1.1);

                        int dr = 1.370705f*v;
                        int dg = -0.698001f*v - 0.337633f*u;
                        int db = 1.732446f*u;

#define setpx                                                   \
                        rgb[px+0] = clamp(rgb[px+0] + dr);      \
                        rgb[px+1] = clamp(rgb[px+1] + dg);      \
                        rgb[px+2] = clamp(rgb[px+2] + db);

                        int px;
                        px = rgbat(y+dy, x+dx+si);
                        setpx;
                        px = rgbat(y+dy+1, x+dx+si);
                        setpx;
                        px = rgbat(y+dy, x+dx+si+1);
                        setpx;
                        px = rgbat(y+dy+1, x+dx+si+1);
                        setpx;
                    }
                }
            }
        }
    }

    FILE *fp = fopen("out.data", "w");
    fwrite(rgb, 1, sizeof(rgb), fp);
    fclose(fp);
}