lib/transcoder.cc


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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/***************************************************************************
 *            transcoder.cc
 *
 *  Wed Jul 19 22:11:02 CEST 2006
 *  Copyright  2006 Bent Bisballe Nyeng
 *  deva@aasimon.org
 ****************************************************************************/

/*
 *  This file is part of MIaV.
 *
 *  MIaV is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  MIaV 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with MIaV; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
 */
#include "transcoder.h"

/*
  R = Y + 1.4075 * (V - 128)
  G = Y - (0.3455 * (U - 128) - (0.7169 * (V - 128))
  B = Y + 1.7790 * (U - 128)
*/
#define RED(y, u, v)   (y + 1.4075 * (v - 128))
#define GREEN(y, u, v) (y - (0.3455 * (u - 128)) - (0.7169 * (v - 128)))
#define BLUE(y, u, v)  (y + 1.7790 * (u - 128))

/*
  R = 1.164(Y - 16) + 1.596(V - 128) 
  G = 1.164(Y - 16) - 0.813(V - 128) - 0.391(U - 128)
  B = 1.164(Y - 16)                  + 2.018(U - 128)
*/
//#define RED(y, u, v)   (1.164 * (y - 16) + 1.596 * (v - 128))
//#define GREEN(y, u, v) (1.164 * (y - 16) - 0.813 * (v - 128) - 0.391 * (u - 128))
//#define BLUE(y, u, v)  (1.164 * (y - 16)                     + 2.018 * (u - 128))
static Frame *transcode_yuv2brg0(Frame *input, char* rgb, int bufsz)
{
  if(!rgb) { // No buffer supplied, creating one.
    rgb = new char[720 * 576 * 4];
    bufsz = 720 * 576 * 4;
  }
  if(bufsz < 720 * 576 * 4) return NULL; // Buffer is too small.

  unsigned char Y0, Y1, U, V;

  unsigned int byte = 0;
  unsigned int pos = 0;

  char *pframe = input->vframe;

  while(pos < 720*576*4) {
    // YUV 4:2:2 packing
    // Y0 U0 Y1 V1 Y2 U2 Y3 V3
    // [Y0 U0 V1] [Y1 U0 V1] [Y2 U2 V3] [Y3 U2 V3]

    Y0 = pframe[byte]; byte++;
    U = pframe[byte]; byte++;
    Y1 = pframe[byte]; byte++;
    V = pframe[byte]; byte++;

    rgb[pos+3] = 0; // Alpha
    rgb[pos+2] = (unsigned char)RED(Y0, U, V); // Red
    rgb[pos+1] = (unsigned char)GREEN(Y0, U, V); // Green
    rgb[pos+0] = (unsigned char)BLUE(Y0, U, V); // Blue
    pos+=4;

    rgb[pos+3] = 0; // Alpha
    rgb[pos+2] = (unsigned char)RED(Y1, U, V); // Red
    rgb[pos+1] = (unsigned char)GREEN(Y1, U, V); // Green
    rgb[pos+0] = (unsigned char)BLUE(Y1, U, V); // Blue
    pos+=4;
  }

  return new Frame(rgb, bufsz, VF_BRG0, NULL, 0, AF_NONE);
}


Frame *transcode(Frame *input,
                 video_format_t vformat, char *vbuffer, int vbuffer_size, 
                 audio_format_t aformat, char *abuffer, int abuffer_size)
{

  // YUV422 => BRG0
  if(vformat == VF_BRG0 && input->vformat == VF_YUV422 && 
     aformat == AF_NONE && abuffer == NULL)
    return transcode_yuv2brg0(input, vbuffer, vbuffer_size);

  // Unknown transcoding!
  return NULL;
}