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Diff of /xvidcore/src/plugins/plugin_2pass2.c

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revision 1.1.2.38, Sun May 9 14:00:35 2004 UTC revision 1.2, Mon Mar 22 22:36:24 2004 UTC
# Line 177  Line 177 
177          twopass_stat_t * stats;          twopass_stat_t * stats;
178    
179          /*----------------------------------          /*----------------------------------
180           * Hysteresis helpers           * Histerysis helpers
181           *--------------------------------*/           *--------------------------------*/
182    
183          /* This field holds the int2float conversion errors of each quant per          /* This field holds the int2float conversion errors of each quant per
# Line 270  Line 270 
270  static void first_pass_stats_prepare_data(rc_2pass2_t * rc);  static void first_pass_stats_prepare_data(rc_2pass2_t * rc);
271  static void first_pass_scale_curve_internal(rc_2pass2_t *rc);  static void first_pass_scale_curve_internal(rc_2pass2_t *rc);
272  static void scaled_curve_apply_advanced_parameters(rc_2pass2_t * rc);  static void scaled_curve_apply_advanced_parameters(rc_2pass2_t * rc);
 #ifdef VBV  
 static  int check_curve_for_vbv_compliancy(rc_2pass2_t * rc, const float fps);  
 static  int scale_curve_for_vbv_compliancy(rc_2pass2_t * rc, const float fps);  
 #endif  
   
273  #if 0  #if 0
274  static void stats_print(rc_2pass2_t * rc);  static void stats_print(rc_2pass2_t * rc);
275  #endif  #endif
# Line 431  Line 426 
426           * shape the curve in the BEFORE/AFTER pair of functions */           * shape the curve in the BEFORE/AFTER pair of functions */
427          scaled_curve_apply_advanced_parameters(rc);          scaled_curve_apply_advanced_parameters(rc);
428    
   
 #ifdef VBV  
 /* Check curve for VBV compliancy and rescale if necessary */  
   
   
 #ifdef VBV_FORCE  
   if (rc->param.vbvsize==0)  
   {  
     rc->param.vbvsize      =  3145728;  
     rc->param.vbvinitial   =  2359296;  
     rc->param.vbv_maxrate  =  4000000;  
     rc->param.vbv_peakrate = 10000000;  
   }  
 #endif  
   
   if (rc->param.vbvsize>0)    /* vbvsize==0 switches VBV check off */  
   {  
     const double fps = (double)create->fbase/(double)create->fincr;  
     int status = check_curve_for_vbv_compliancy(rc, fps);  
 #ifdef VBV_DEBUG  
     if (status)  
       fprintf(stderr,"underflow detected\n Scaling Curve for compliancy... ");  
 #endif  
   
         status = scale_curve_for_vbv_compliancy(rc, fps);  
   
 #ifdef VBV_DEBUG  
       if (status==0)  
         fprintf(stderr,"done.\n");  
       else  
         fprintf(stderr,"impossible.\n");  
 #endif  
   }  
 #endif  
   
429          *handle = rc;          *handle = rc;
430          return(0);          return(0);
431  }  }
# Line 1420  Line 1380 
1380          return;          return;
1381  }  }
1382    
   
 #ifdef VBV  
   
 /*****************************************************************************  
  * VBV compliancy check and scale  
  * MPEG-4 standard specifies certain restrictions for bitrate/framesize in VBR  
  * to enable playback on devices with limited readspeed and memory (and which  
  * aren't...)  
  *  
  * DivX profiles have 2 criteria: VBV as in MPEG standard  
  *                                a limit on peak bitrate for any 3 seconds  
  *  
  * But if VBV is fulfilled, peakrate is automatically fulfilled in any profile  
  * define so far, so we check for it (for completeness) but correct only VBV  
  *  
  *****************************************************************************/  
   
 #define VBV_COMPLIANT 0  
 #define VBV_UNDERFLOW 1 /* video buffer runs empty */  
 #define VBV_OVERFLOW 2  /* doesn't exist for VBR encoding */  
 #define VBV_PEAKRATE 4  /* peak bitrate (within 3s) violated */  
   
 static int check_curve_for_vbv_compliancy(rc_2pass2_t * rc, const float fps)  
 {  
 /* We do all calculations in float, for higher accuracy, and bytes for convenience  
   
    typical values from DivX Home Theater profile:  
    vbvsize= 384*1024 (384kB), vbvinitial= 288*1024 (75% fill)  
    maxrate= 4000000 (4MBps), peakrate= 10000000 (10MBps)  
   
    PAL: offset3s = 75 (3 seconds of 25fps)  
    NTSC: offset3s = 90 (3 seconds of 29.97fps) or 72 (3 seconds of 23.976fps)  
 */  
   
   const float vbvsize = (float)rc->param.vbvsize/8.f;  
   float vbvfill = (float)rc->param.vbvinitial/8.f;  
   
   const float maxrate = (float)rc->param.vbv_maxrate;  
   const float peakrate = (float)rc->param.vbv_peakrate;  
   const float r0 = (int)(maxrate/fps+0.5)/8.f;  
   
   int bytes3s = 0;  
   int offset3s = (int)(3.f*fps+0.5);  
   
   int i;  
   for (i=0; i<rc->num_frames; i++) {  
 /* DivX 3s peak bitrate check  */  
   
     bytes3s += rc->stats[i].scaled_length;  
     if (i>=offset3s)  
       bytes3s -= rc->stats[i-offset3s].scaled_length;  
   
     if (8.f*bytes3s > 3*peakrate)  
       return VBV_PEAKRATE;  
   
 /* update vbv fill level */  
   
     vbvfill += r0 - rc->stats[i].scaled_length;  
   
 /* this check is _NOT_ an "overflow"! only reading from disk stops then */  
     if (vbvfill > vbvsize)  
       vbvfill = vbvsize;  
   
 /* but THIS would be an underflow. report it! */  
     if (vbvfill < 0)  
       return VBV_UNDERFLOW;  
   }  
   
   return VBV_COMPLIANT;  
 }  
 /* idea: min(vbvfill) could be stored to print "minimum buffer fill" */  
   
   
   
 static int scale_curve_for_vbv_compliancy(rc_2pass2_t * rc, const float fps)  
 {  
 /* correct any VBV violations. Peak bitrate violations disappears  
    by this automatically  
   
    This implementation follows  
   
    Westerink, Rajagopalan, Gonzales "Two-pass MPEG-2 variable-bitrate encoding"  
    IBM J. RES. DEVELOP. VOL 43, No. 4, July 1999, p.471--488  
   
    Thanks, guys! This paper rocks!!!  
 */  
   
 /*  
     For each scene of len N, we have to check up to N^2 possible buffer fills.  
     This works well with MPEG-2 where N==12 or so, but for MPEG-4 it's a  
     little slow...  
 */  
   const float vbvsize = (float)rc->param.vbvsize/8.f;  
   const float vbvinitial = (float)rc->param.vbvinitial/8.f;  
   
   const float maxrate = 0.9*rc->param.vbv_maxrate;  
   const float vbvlow = 0.10f*vbvsize;  
   const float r0 = (int)(maxrate/fps+0.5)/8.f;  
   
   int i,k,l,n,violation = 0;  
   float *scenefactor;  
   int *scenestart;  
   int *scenelength;  
   
 /* first step: determine how many "scenes" there are and store their boundaries  
    we could get all this from existing keyframe_positions, somehow, but there we  
    don't have a min_scenelength, and it's no big deal to get it again.  */  
   
   const int min_scenelength = 50;  
   int num_scenes = 0;  
   int last_scene = -999;  
   for (i=0; i<rc->num_frames; i++) {  
     if ( (rc->stats[i].type == XVID_TYPE_IVOP) && (i-last_scene>min_scenelength) )  
     {  
       last_scene = i;  
       num_scenes++;  
     }  
   }  
   
   scenefactor = (float*)malloc( num_scenes*sizeof(float) );  
   scenestart = (int*)malloc( num_scenes*sizeof(int) );  
   scenelength = (int*)malloc( num_scenes*sizeof(int) );  
   
   if ((!scenefactor) || (!scenestart) || (!scenelength) )  
   {  
     free(scenefactor);  
     free(scenestart);  
     free(scenelength);  
     /* remember: free(0) is valid and does exactly nothing. */  
     return -1;  
   }  
   
 /* count again and safe the length/position */  
   
   num_scenes = 0;  
   last_scene = -999;  
   for (i=0; i<rc->num_frames; i++) {  
     if ( (rc->stats[i].type == XVID_TYPE_IVOP) && (i-last_scene>min_scenelength) )  
     {  
       if (num_scenes>0)  
         scenelength[num_scenes-1]=i-last_scene;  
       scenestart[num_scenes]=i;  
       num_scenes++;  
       last_scene = i;  
     }  
   }  
   scenelength[num_scenes-1]=i-last_scene;  
   
 /* second step: check for each scene, how much we can scale its frames up or down  
    such that the VBV restriction is just fulfilled  
 */  
   
   
 #define R(k,n) (((n)+1-(k))*r0)     /* how much enters the buffer between frame k and n */  
   for (l=0; l<num_scenes;l++)  
   {  
     const int start = scenestart[l];  
     const int length = scenelength[l];  
     twopass_stat_t * frames = &rc->stats[start];  
   
     float S0n,Skn;  
     float f,minf = 99999.f;  
   
     S0n=0.;  
     for (n=0;n<=length-1;n++)  
     {  
       S0n += frames[n].scaled_length;  
   
       k=0;  
       Skn = S0n;  
       f = (R(k,n-1) + (vbvinitial - vbvlow)) / Skn;  
       if (f < minf)  
         minf = f;  
   
       for (k=1;k<=n;k++)  
       {  
         Skn -= frames[k].scaled_length;  
   
         f = (R(k,n-1) + (vbvsize - vbvlow)) / Skn;  
         if (f < minf)  
           minf = f;  
       }  
     }  
   
     /* special case: at the end, fill buffer up to vbvinitial again  
        TODO: Allow other values for buffer fill between scenes  
        e.g. if n=N is smallest f-value, then check for better value */  
   
     n=length;  
     k=0;  
     Skn = S0n;  
     f = R(k,n-1)/Skn;  
     if (f < minf)  
       minf = f;  
   
     for (k=1;k<=n-1;k++)  
     {  
       Skn -= frames[k].scaled_length;  
   
       f = (R(k,n-1) + (vbvinitial - vbvlow)) / Skn;  
       if (f < minf)  
         minf = f;  
     }  
   
 #ifdef VBV_DEBUG  
     printf("Scene %d (Frames %d-%d): VBVfactor %f\n", l, start, start+length-1 , minf);  
 #endif  
   
     scenefactor[l] = minf;  
   }  
 #undef R  
   
 /* last step: now we know of any scene how much it can be scaled up or down without  
    violating VBV. Next, distribute bits from the evil scenes to the good ones */  
   
   do  
   {  
     float S_red = 0.f;    /* how much to redistribute */  
     float S_elig = 0.f;   /* sum of bit for those scenes you can still swallow something*/  
     int l;  
   
     for (l=0;l<num_scenes;l++)   /* check how much is wrong */  
     {  
     const int start = scenestart[l];  
     const int length = scenelength[l];  
     twopass_stat_t * frames = &rc->stats[start];  
   
       if (scenefactor[l] == 1.) /* exactly 1 means "don't touch this anymore!" */  
         continue;  
   
       if (scenefactor[l] > 1.) /* within limits */  
       {  
         for (n= 0; n < length; n++)  
           S_elig += frames[n].scaled_length;  
       }  
       else /* underflowing segment */  
       {  
         for (n= 0; n < length; n++)  
         {  
           float newbytes = (float)frames[n].scaled_length * scenefactor[l];  
           S_red += (float)frames[n].scaled_length - (float)newbytes;  
           frames[n].scaled_length =(int)newbytes;  
         }  
         scenefactor[l] = 1.f;  
       }  
     }  
   
     if (S_red < 1.f)   /* no more underflows */  
       break;  
   
     if (S_elig < 1.f)  
     {  
 #ifdef VBV_DEBUG  
       fprintf(stderr,"Everything underflowing. \n");  
 #endif  
       free(scenefactor);  
       free(scenestart);  
       free(scenelength);  
       return -2;  
     }  
   
     const float f_red = (1.f + S_red/S_elig);  
   
 #ifdef VBV_DEBUG  
     printf("Moving %.0f kB to avoid buffer underflow, correction factor: %.5f\n",S_red/1024.f,f_red);  
 #endif  
   
     violation=0;  
     for (l=0; l<num_scenes; l++)   /* scale remaining scenes up to meet total size */  
     {  
       const int start = scenestart[l];  
       const int length = scenelength[l];  
       twopass_stat_t * frames = &rc->stats[start];  
   
       if (scenefactor[l] == 1.)  
         continue;  
   
       /* there shouldn't be any segments with factor<1 left, so all the rest is >1 */  
   
       for (n= 0; n < length; n++)  
       {  
         frames[n].scaled_length = (int)(frames[n].scaled_length * f_red + 0.5);  
       }  
   
       scenefactor[l] /= f_red;  
       if (scenefactor[l] < 1.f)  
         violation=1;  
     }  
   
   } while (violation);  
   
   free(scenefactor);  
   free(scenestart);  
   free(scenelength);  
   return 0;  
 }  
   
   
 #endif  
   
   
1383  /*****************************************************************************  /*****************************************************************************
1384   * Still more low level stuff (nothing to do with stats treatment)   * Still more low level stuff (nothing to do with stats treatment)
1385   ****************************************************************************/   ****************************************************************************/
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