scenecut.c

Nokia H.264/AVC Encoder/Decoder Usage Manual

/*
COPYRIGHT, LICENSE AND WARRANTY INFORMATION

This software module has been originally developed by Nokia Corporation. 

Provided that a person, entity or a company willing to use the Software 
(hereinafter Licensee) comply with all the terms and conditions of this 
Statement and subject to the limitations set forth in this Statement Nokia 
grants to such Licensee a non-exclusive, sub-licensable, worldwide, 
limited license under copyrights owned by Nokia to use the Software for 
the sole purpose of creating, manufacturing, selling, marketing, or  
distributing (including the right to make modifications to the Software) 
a fully compliant decoder implementation (hereinafter "Decoder") of 
ITU-T Recommendation H.264 / ISO/IEC International Standard 14496-10 and 
an encoder implementation producing output that is decodable with the 
Decoder.

Nokia retains the ownership of copyrights to the Software. There is no 
patent nor other intellectual property right of Nokia licensed under this 
Statement (except the copyright license above). Licensee hereby assumes 
sole responsibility to secure any other intellectual property rights 
needed, if any. For example, if patent licenses  are required, it is 
their responsibility to acquire the license before utilizing the Software.

The license by Nokia is subject to that the Licensee grants to Nokia the 
non-exclusive, worldwide, royalty-free, perpetual and irrevocable 
covenant that the Licensee(s) shall not bring a suit before any court or 
administrative agency or otherwise assert a claim for infringement under 
the Licensee intellectual property rights that, but for a license, would 
be infringed by the Software against  
   (a)  Nokia or Nokia's Affiliate; or  
   (b)  other recipient of a license and covenant not to sue with respect 
        to the Software from Nokia; or 
   (c)  contractor, customer or distributor of a party listed above in a 
        or b,  
which suit or claim is related to the Software or use thereof.

The Licensee(s) further agrees to grant a reciprocal license to Nokia 
(as granted by Nokia to the Licensee(s) on the modifications made by 
Licensee(s) to the Software. 

THE SOFTWARE IS PROVIDED "AS IS" AND THE ORIGINAL DEVELOPER DISCLAIMS 
ANY AND ALL WARRANTIES WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING 
BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS 
FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. THOSE INTENDING TO USE 
THE SOFTWARE ARE EXPRESSLY ADVISED THAT ITS USE MAY INFRINGE EXISTING 
PATENTS AND BE SUBJECT TO ROYALTY PAYMENTS TO PATENT OWNERS. ANYONE 
USING THE SOFTWARE ON THE BASIS OF THIS LICENSE AGREES TO OBTAIN THE 
NECESSARY PERMISSIONS FROM ANY AND ALL APPLICABLE PATENT OWNERS FOR SUCH 
USE.

IN NO EVENT SHALL THE ORIGINAL DEVELOPER BE LIABLE FOR ANY CLAIM, 
DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT 
OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE 
OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

This copyright, license and warranty information notice must be retained 
in all copies and derivative works of the Software or substantial 
portions thereof.
*/



#include <stdio.h>
#include <string.h>
#include "scenecut.h"
#ifdef PERFORMANCE
#include "timer.h"
#endif
/*
 * Define local function prototypes.
 */

static int32 Diff_of_Q_Histograms(u_int8 *ptr1, u_int8 *ptr2, int32 fr_size);





#ifdef PERFORMANCE
static int histStart = 0, histStop = 0, diffStart = 0, diffStop = 0; 
extern int histTotal, diffTotal;
#endif

/*
 *
 * scdSceneCut
 *
 * Parameters:
 *      ycurr        current frame
 *    ucurr
 *    vcurr
 *      yprev        previous frame
 *    uprev
 *    vprev
 *      sizex        width of a luminanceframe in pixels
 *      sizey        height of a luminanceframe in pixels
 *      subfactor    Chrominance subsampling factor (4:2:0 = 4, 4:2:2 = 2 etc.)
 *
 * Function:
 *      Examines if there is a scene cut between frames fr1 and fr2
 *      using local function Sum_of_Q_Histograms
 *
 * Returns:
 *      1, if there is a scene cut, 0 otherwise
 *
 */
int32 scdSceneCut(u_int8 *ycurr, u_int8 *ucurr, u_int8 *vcurr, u_int8 *yprev, u_int8 *uprev, u_int8 *vprev,
         int32 sizex, int32 sizey, int32 subfactor, int *sumy, int *sumuv)
{
  int32 threshold_y1, threshold_y2, threshold_uv, sum_y = 0, sum_uv = 0;

  /* compare y-frames */
  sum_y = Diff_of_Q_Histograms(ycurr, yprev, sizex*sizey);
  *sumy = SUMY = sum_y;
  *sumuv = 0;
  
  /* there is definitely a scene cut if half of the colour is changed 
    the abs sum of difference of histograms is two times the size of
    the frames */
  threshold_y1 = QCIF_THRESHOLD_Y_HIGH;
  
  /* adapt the threshold */
  threshold_y1 = (int32)( (float32)threshold_y1 * ((float32)(sizex*sizey)/25344.0) );
  
  if (sum_y > threshold_y1) {
    return 1;
  }
  else {
    threshold_y2 = QCIF_THRESHOLD_Y_LOW;
      
    /* adapt the threshold */
    threshold_y2 = (int32)( (float32)threshold_y2 * ((float32)(sizex*sizey)/25344.0) );

    if (sum_y > threshold_y2) {

      /* compare v-frames */
      *sumuv = sum_uv = Diff_of_Q_Histograms(vcurr, vprev, sizey*sizex/subfactor);
      threshold_uv = QCIF_THRESHOLD_UV;
    

      /* adapt the threshold */
      threshold_uv = (int32)( (float32)threshold_uv * ( (float32)(sizex*sizey*4)/(float32)(subfactor*25344) ));

      /* if sum_y is in a upper half of the gray area, sum_uv can be lower
        than usually */
   
      if ((sum_uv > threshold_uv) || 
        ((sum_y > (threshold_y1 + threshold_y2)/2)&&
        (sum_uv > threshold_uv*4/5))) {
      
        return 1;
      }

      else {

        /* compare u-frames */
        sum_uv = Diff_of_Q_Histograms(ucurr, uprev, sizey*sizex/subfactor); 


        /* if sum_y is in a upper half of the gray area, sum_uv can be 
          lower than usually */
       
        if ((sum_uv > threshold_uv) ||
          ((sum_y > (threshold_y1 + threshold_y2)/2)&&
          (sum_uv > threshold_uv*4/5))) {

          return 1;
        }
      }
    }
  }
  return 0;
}


/*
 *
 * Diff_of_Q_Histograms
 *
 * Parameters:
 *      ptr1         y-, u- or v-component of current frame
 *      ptr2         y-, u- or v-component of previous frame
 *      fr_size      sizex*sizey of components
 *
 * Function:
 *      Calculates histograms of 32 bin of both ptr's, calculates their
 *      difference and sums the absolute values of the difference
 *
 * Returns:
 *      sum of absolute difference of quantized (32 bin) histograms
 *
 */
static int32 Diff_of_Q_Histograms(u_int8 *ptr1, u_int8 *ptr2, int32 fr_size)
{
  int16 i; 
  int32 j, s = 0, hist1[32], hist2[32];

  memset( hist1, 0, 32*sizeof(int) );
  memset( hist2, 0, 32*sizeof(int) );

#ifdef PERFORMANCE
  histStart = tmrGetTime();
#endif
  /* calculate histograms */
  for(j = 0; j < fr_size; j++) {
    hist1[(int) ptr1[j] >> 3]++;
    hist2[(int) ptr2[j] >> 3]++;
    }
#ifdef PERFORMANCE
  histStop = tmrGetTime();
  histTotal += histStop - histStart;

  diffStart = tmrGetTime();
#endif

  /* calculate the difference */
  for (i = 0; i < 32; i++)
    s += abs(hist2[i] - hist1[i]);

#ifdef PERFORMANCE
  diffStop = tmrGetTime();
  diffTotal += diffStop - diffStart;
#endif
  
  return s;
}