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hm12.c

/*

cx2341x HM12 conversion routines

(C) 2009 Hans Verkuil <hverkuil@xs4all.nl>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */

#include "libv4lconvert-priv.h"
#include <string.h>

/* The HM12 format is used in the Conexant cx23415/6/8 MPEG encoder devices.
   It is a macroblock format with separate Y and UV planes, each plane
   consisting of 16x16 values. All lines are always 720 bytes long. If the
   width of the image is less than 720, then the remainder is padding.

   The height has to be a multiple of 32 in order to get correct chroma
   values.

   It is basically a by-product of the MPEG encoding inside the device,
   which is available for raw video as a 'bonus feature'.
 */

#define CLIP(color) \
      (unsigned char)(((color) > 0xff) ? 0xff : (((color) < 0) ? 0 : (color)))

static const int stride = 720;

static void v4lconvert_hm12_to_rgb(const unsigned char *src, unsigned char *dest,
            int width, int height, int rgb)
{
      unsigned int y, x, i, j;
      const unsigned char *y_base = src;
      const unsigned char *uv_base = src + stride * height;
      const unsigned char *src_y;
      const unsigned char *src_uv;
      int mb_size = 256;
      int r = rgb ? 0 : 2;
      int b = 2 - r;

      for (y = 0; y < height; y += 16) {
            int mb_y = (y / 16) * (stride / 16);
            int mb_uv = (y / 32) * (stride / 16);
            int maxy = (height - y < 16 ? height - y : 16);

            for (x = 0; x < width; x += 16, mb_y++, mb_uv++) {
                  int maxx = (width - x < 16 ? width - x : 16);

                  src_y = y_base + mb_y * mb_size;
                  src_uv = uv_base + mb_uv * mb_size;

                  if (y & 0x10)
                        src_uv += mb_size / 2;

                  for (i = 0; i < maxy; i++) {
                        int idx = (x + (y + i) * width) * 3;

                        for (j = 0; j < maxx; j++) {
                              int y = src_y[j];
                              int u = src_uv[j & ~1];
                              int v = src_uv[j | 1];
                              int u1 = (((u - 128) << 7) + (u - 128)) >> 6;
                              int rg = (((u - 128) << 1) + (u - 128) +
                                    ((v - 128) << 2) + ((v - 128) << 1)) >> 3;
                              int v1 = (((v - 128) << 1) + (v - 128)) >> 1;

                              dest[idx+r] = CLIP(y + v1);
                              dest[idx+1] = CLIP(y - rg);
                              dest[idx+b] = CLIP(y + u1);
                              idx += 3;
                        }
                        src_y += 16;
                        if (i & 1)
                              src_uv += 16;
                  }
            }
      }
}

void v4lconvert_hm12_to_rgb24(const unsigned char *src, unsigned char *dest,
            int width, int height)
{
      v4lconvert_hm12_to_rgb(src, dest, width, height, 1);
}

void v4lconvert_hm12_to_bgr24(const unsigned char *src, unsigned char *dest,
            int width, int height)
{
      v4lconvert_hm12_to_rgb(src, dest, width, height, 0);
}

static void de_macro_uv(unsigned char *dstu, unsigned char *dstv,
            const unsigned char *src, int w, int h)
{
      unsigned int y, x, i, j;

      for (y = 0; y < h; y += 16) {
            for (x = 0; x < w; x += 8) {
                  const unsigned char *src_uv = src + y * stride + x * 32;
                  int maxy = (h - y < 16 ? h - y : 16);
                  int maxx = (w - x < 8 ? w - x : 8);

                  for (i = 0; i < maxy; i++) {
                        int idx = x + (y + i) * w;

                        for (j = 0; j < maxx; j++) {
                              dstu[idx+j] = src_uv[2 * j];
                              dstv[idx+j] = src_uv[2 * j + 1];
                        }
                        src_uv += 16;
                  }
            }
      }
}

static void de_macro_y(unsigned char *dst, const unsigned char *src,
            int w, int h)
{
      unsigned int y, x, i;

      for (y = 0; y < h; y += 16) {
            for (x = 0; x < w; x += 16) {
                  const unsigned char *src_y = src + y * stride + x * 16;
                  int maxy = (h - y < 16 ? h - y : 16);
                  int maxx = (w - x < 16 ? w - x : 16);

                  for (i = 0; i < maxy; i++) {
                        memcpy(dst + x + (y + i) * w, src_y, maxx);
                        src_y += 16;
                  }
            }
      }
}

void v4lconvert_hm12_to_yuv420(const unsigned char *src, unsigned char *dest,
            int width, int height, int yvu)
{
      de_macro_y(dest, src, width, height);
      dest += width * height;
      src += stride * height;
      if (yvu)
            de_macro_uv(dest + width * height / 4, dest, src, width / 2, height / 2);
      else
            de_macro_uv(dest, dest + width * height / 4, src, width / 2, height / 2);
}

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