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

-revision 1382, Mon Mar 22 22:36:25 2004 UTC
+revision 1470, Thu Jun 10 18:13:42 2004 UTC
 Line 25
   *  along with this program; if not, write to the Free Software
   *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   *
-  * $Id: plugin_2pass2.c,v 1.2 2004-03-22 22:36:24 edgomez Exp $
+  * $Id: plugin_2pass2.c,v 1.3 2004-06-10 18:13:42 chl Exp $
   *
   *****************************************************************************/
 Line 177
          twopass_stat_t * stats;
          /*----------------------------------
-          * Histerysis helpers
+          * Hysteresis helpers
           *--------------------------------*/
          /* This field holds the int2float conversion errors of each quant per
 Line 270
  static void first_pass_stats_prepare_data(rc_2pass2_t * rc);
  static void first_pass_scale_curve_internal(rc_2pass2_t *rc);
  static void scaled_curve_apply_advanced_parameters(rc_2pass2_t * rc);
+ 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);
  #if 0
  static void stats_print(rc_2pass2_t * rc);
  #endif
-Line 426
+Line 428
           * shape the curve in the BEFORE/AFTER pair of functions */
          scaled_curve_apply_advanced_parameters(rc);
+ /* Check curve for VBV compliancy and rescale if necessary */
+ #ifdef VBV_FORCE
+   if (rc->param.vbv_size==0)
+   {
+     rc->param.vbv_size      =  3145728;
+     rc->param.vbv_initial   =  2359296;
+     rc->param.vbv_maxrate  =  4000000;
+     rc->param.vbv_peakrate = 10000000;
+   }
+ #endif
+   if (rc->param.vbv_size>0)    /* vbv_size==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
+   }
          *handle = rc;
          return(0);
  }
-Line 1381
+Line 1413
  }
  /*****************************************************************************
+  * 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 in bytes for convenience
+    typical values from DivX Home Theater profile:
+    vbv_size= 384*1024 (384kB), vbv_initial= 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 vbv_size = (float)rc->param.vbv_size/8.f;
+   float vbvfill = (float)rc->param.vbv_initial/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 > vbv_size)
+       vbvfill = vbv_size;
+ /* but THIS would be an underflow. report it! */
+     if (vbvfill < 0)
+       return VBV_UNDERFLOW;
+   }
+   return VBV_COMPLIANT;
+ }
+ /* TODO: store min(vbvfill) and 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...
+     TODO: Better control on VBVfill between scenes
+ */
+   const float vbv_size = (float)rc->param.vbv_size/8.f;
+   const float vbv_initial = (float)rc->param.vbv_initial/8.f;
+   const float maxrate = 0.9*rc->param.vbv_maxrate;
+   const float vbv_low = 0.10f*vbv_size;
+   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 = (int)(fps+0.5);
+   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) + (vbv_initial - vbv_low)) / Skn;
+       if (f < minf)
+         minf = f;
+       for (k=1;k<=n;k++)
+       {
+         Skn -= frames[k].scaled_length;
+         f = (R(k,n-1) + (vbv_size - vbv_low)) / Skn;
+         if (f < minf)
+           minf = f;
+       }
+     }
+     /* special case: at the end, fill buffer up to vbv_initial 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) + (vbv_initial - vbv_low)) / 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;
+ }
+ /*****************************************************************************
   * Still more low level stuff (nothing to do with stats treatment)
   ****************************************************************************/

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