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

-revision 1.2, Mon Mar 22 22:36:24 2004 UTC
+revision 1.7, Sun Mar 27 03:59:42 2005 UTC
 Line 35
  /* forces second pass not to be bigger than first */
  #undef PASS_SMALLER
- /* automtically alters overflow controls (strength and improvement/degradation)
+ /* automatically alters overflow controls (strength and improvement/degradation)
          to fight most common problems without user's knowladge */
  #define SMART_OVERFLOW_SETTING
 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 288
+Line 290
          if (rc == NULL)
                  return XVID_ERR_MEMORY;
-         rc->param = *param;
+         /* v1.0.x */
+         rc->param.version = param->version;
+         rc->param.bitrate = param->bitrate;
+         rc->param.filename = param->filename;
+         rc->param.keyframe_boost = param->keyframe_boost;
+         rc->param.curve_compression_high = param->curve_compression_high;
+         rc->param.curve_compression_low = param->curve_compression_low;
+         rc->param.overflow_control_strength = param->overflow_control_strength;
+         rc->param.max_overflow_improvement = param->max_overflow_improvement;
+         rc->param.max_overflow_degradation = param->max_overflow_degradation;
+         rc->param.kfreduction = param->kfreduction;
+         rc->param.kfthreshold = param->kfthreshold;
+         rc->param.container_frame_overhead = param->container_frame_overhead;
+         if (XVID_VERSION_MINOR(param->version) >= 1) {
+                 rc->param.vbv_size = param->vbv_size;
+                 rc->param.vbv_initial = param->vbv_initial;
+                 rc->param.vbv_maxrate = param->vbv_maxrate;
+                 rc->param.vbv_peakrate = param->vbv_peakrate;
+         }else{
+                 rc->param.vbv_size =
+                 rc->param.vbv_initial =
+                 rc->param.vbv_maxrate =
+                 rc->param.vbv_peakrate = 0;
+         }
          /* Initialize all defaults */
  #define _INIT(a, b) if((a) <= 0) (a) = (b)
-Line 426
+Line 452
           * 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   =  4854000;
+                 rc->param.vbv_peakrate  =  8000000;
+         }
+ #endif
+         /* vbv_size==0 switches VBV check off */
+         if (rc->param.vbv_size > 0)  {
+                 const double fps = (double)create->fbase/(double)create->fincr;
+                 int status = check_curve_for_vbv_compliancy(rc, fps);
+                 if (status) {
+                         DPRINTF(XVID_DEBUG_RC, "[xvid rc] Underflow detected - Scaling Curve for compliancy.\n");
+                 }
+                 status = scale_curve_for_vbv_compliancy(rc, fps);
+                 if (status == 0) {
+                         DPRINTF(XVID_DEBUG_RC, "[xvid rc] VBV compliant curve scaling done.\n");
+                 } else {
+                         DPRINTF(XVID_DEBUG_RC, "[xvid rc] VBV compliant curve scaling impossible.\n");
+                 }
+         }
          *handle = rc;
          return(0);
  }
-Line 804
+Line 857
                  rc->KFoverflow -= rc->KFoverflow_partial;
          }
-         rc->overflow += (s->error = s->desired_length - data->length);
+         s->error = s->desired_length - data->length;
          rc->real_total += data->length;
          DPRINTF(XVID_DEBUG_RC, "[xvid rc] -- frame:%d type:%c quant:%d stats:%d scaled:%d desired:%d actual:%d error:%d overflow:%.2f\n",
-Line 1381
+Line 1434
  }
  /*****************************************************************************
+  * 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= 4854000 (4.854MBps)
+          *  peakrate= 8000000 (8MBps)
+          *
+          *  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;
+         float vbvmin;
+         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;
+         /* 1Gbit should be enough to inuitialize the vbvmin
+          *      an arbitrary high value */
+         vbvmin = 1000*1000*1000;
+         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;
+     /* ignore peakrate constraint if peakrate is <= 0.f */
+                 if (peakrate>0.f && 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);
+                 /* Store the minimum buffer filling */
+                 if (vbvfill < vbvmin)
+                         vbvmin = vbvfill;
+         }
+         DPRINTF(XVID_DEBUG_RC, "[xvid rc] Minimum buffer fill: %f bytes\n", vbvmin);
+         return(VBV_COMPLIANT);
+ }
+ 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;
+                 }
+                 DPRINTF(XVID_DEBUG_RC, "[xvid rc] Scene %d (Frames %d-%d): VBVfactor %f\n",
+                                 l, start, start+length-1 , minf);
+                 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*/
+                 float f_red;
+                 int l;
+                 /* check how much is wrong */
+                 for (l=0;l<num_scenes;l++) {
+                         const int start = scenestart[l];
+                         const int length = scenelength[l];
+                         twopass_stat_t * frames = &rc->stats[start];
+                         /* exactly 1 means "don't touch this anymore!" */
+                         if (scenefactor[l] == 1.)
+                                 continue;
+                         /* within limits */
+                         if (scenefactor[l] > 1.) {
+                                 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;
+                         }
+                 }
+                 /* no more underflows */
+                 if (S_red < 1.f)
+                         break;
+                 if (S_elig < 1.f) {
+                         DPRINTF(XVID_DEBUG_RC, "[xvid rc] Everything underflowing.\n");
+                         free(scenefactor);
+                         free(scenestart);
+                         free(scenelength);
+                         return(-2);
+                 }
+                 f_red = (1.f + S_red/S_elig);
+                 DPRINTF(XVID_DEBUG_RC, "[xvid rc] Moving %.0f kB to avoid buffer underflow, correction factor: %.5f\n",
+                                 S_red/1024.f, f_red);
+                 violation=0;
+                 /* scale remaining scenes up to meet total size */
+                 for (l=0; l<num_scenes; l++) {
+                         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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