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revision 1.1.2.37, Sat Jan 31 14:51:56 2004 UTC revision 1.1.2.38, Sun May 9 14:00:35 2004 UTC
# Line 177  Line 177 
177          twopass_stat_t * stats;          twopass_stat_t * stats;
178    
179          /*----------------------------------          /*----------------------------------
180           * Histerysis helpers           * Hysteresis 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);
273    #ifdef VBV
274    static  int check_curve_for_vbv_compliancy(rc_2pass2_t * rc, const float fps);
275    static  int scale_curve_for_vbv_compliancy(rc_2pass2_t * rc, const float fps);
276    #endif
277    
278  #if 0  #if 0
279  static void stats_print(rc_2pass2_t * rc);  static void stats_print(rc_2pass2_t * rc);
280  #endif  #endif
# Line 426  Line 431 
431           * shape the curve in the BEFORE/AFTER pair of functions */           * shape the curve in the BEFORE/AFTER pair of functions */
432          scaled_curve_apply_advanced_parameters(rc);          scaled_curve_apply_advanced_parameters(rc);
433    
434    
435    #ifdef VBV
436    /* Check curve for VBV compliancy and rescale if necessary */
437    
438    
439    #ifdef VBV_FORCE
440      if (rc->param.vbvsize==0)
441      {
442        rc->param.vbvsize      =  3145728;
443        rc->param.vbvinitial   =  2359296;
444        rc->param.vbv_maxrate  =  4000000;
445        rc->param.vbv_peakrate = 10000000;
446      }
447    #endif
448    
449      if (rc->param.vbvsize>0)    /* vbvsize==0 switches VBV check off */
450      {
451        const double fps = (double)create->fbase/(double)create->fincr;
452        int status = check_curve_for_vbv_compliancy(rc, fps);
453    #ifdef VBV_DEBUG
454        if (status)
455          fprintf(stderr,"underflow detected\n Scaling Curve for compliancy... ");
456    #endif
457    
458            status = scale_curve_for_vbv_compliancy(rc, fps);
459    
460    #ifdef VBV_DEBUG
461          if (status==0)
462            fprintf(stderr,"done.\n");
463          else
464            fprintf(stderr,"impossible.\n");
465    #endif
466      }
467    #endif
468    
469          *handle = rc;          *handle = rc;
470          return(0);          return(0);
471  }  }
# Line 1380  Line 1420 
1420          return;          return;
1421  }  }
1422    
1423    
1424    #ifdef VBV
1425    
1426    /*****************************************************************************
1427     * VBV compliancy check and scale
1428     * MPEG-4 standard specifies certain restrictions for bitrate/framesize in VBR
1429     * to enable playback on devices with limited readspeed and memory (and which
1430     * aren't...)
1431     *
1432     * DivX profiles have 2 criteria: VBV as in MPEG standard
1433     *                                a limit on peak bitrate for any 3 seconds
1434     *
1435     * But if VBV is fulfilled, peakrate is automatically fulfilled in any profile
1436     * define so far, so we check for it (for completeness) but correct only VBV
1437     *
1438     *****************************************************************************/
1439    
1440    #define VBV_COMPLIANT 0
1441    #define VBV_UNDERFLOW 1 /* video buffer runs empty */
1442    #define VBV_OVERFLOW 2  /* doesn't exist for VBR encoding */
1443    #define VBV_PEAKRATE 4  /* peak bitrate (within 3s) violated */
1444    
1445    static int check_curve_for_vbv_compliancy(rc_2pass2_t * rc, const float fps)
1446    {
1447    /* We do all calculations in float, for higher accuracy, and bytes for convenience
1448    
1449       typical values from DivX Home Theater profile:
1450       vbvsize= 384*1024 (384kB), vbvinitial= 288*1024 (75% fill)
1451       maxrate= 4000000 (4MBps), peakrate= 10000000 (10MBps)
1452    
1453       PAL: offset3s = 75 (3 seconds of 25fps)
1454       NTSC: offset3s = 90 (3 seconds of 29.97fps) or 72 (3 seconds of 23.976fps)
1455    */
1456    
1457      const float vbvsize = (float)rc->param.vbvsize/8.f;
1458      float vbvfill = (float)rc->param.vbvinitial/8.f;
1459    
1460      const float maxrate = (float)rc->param.vbv_maxrate;
1461      const float peakrate = (float)rc->param.vbv_peakrate;
1462      const float r0 = (int)(maxrate/fps+0.5)/8.f;
1463    
1464      int bytes3s = 0;
1465      int offset3s = (int)(3.f*fps+0.5);
1466    
1467      int i;
1468      for (i=0; i<rc->num_frames; i++) {
1469    /* DivX 3s peak bitrate check  */
1470    
1471        bytes3s += rc->stats[i].scaled_length;
1472        if (i>=offset3s)
1473          bytes3s -= rc->stats[i-offset3s].scaled_length;
1474    
1475        if (8.f*bytes3s > 3*peakrate)
1476          return VBV_PEAKRATE;
1477    
1478    /* update vbv fill level */
1479    
1480        vbvfill += r0 - rc->stats[i].scaled_length;
1481    
1482    /* this check is _NOT_ an "overflow"! only reading from disk stops then */
1483        if (vbvfill > vbvsize)
1484          vbvfill = vbvsize;
1485    
1486    /* but THIS would be an underflow. report it! */
1487        if (vbvfill < 0)
1488          return VBV_UNDERFLOW;
1489      }
1490    
1491      return VBV_COMPLIANT;
1492    }
1493    /* idea: min(vbvfill) could be stored to print "minimum buffer fill" */
1494    
1495    
1496    
1497    static int scale_curve_for_vbv_compliancy(rc_2pass2_t * rc, const float fps)
1498    {
1499    /* correct any VBV violations. Peak bitrate violations disappears
1500       by this automatically
1501    
1502       This implementation follows
1503    
1504       Westerink, Rajagopalan, Gonzales "Two-pass MPEG-2 variable-bitrate encoding"
1505       IBM J. RES. DEVELOP. VOL 43, No. 4, July 1999, p.471--488
1506    
1507       Thanks, guys! This paper rocks!!!
1508    */
1509    
1510    /*
1511        For each scene of len N, we have to check up to N^2 possible buffer fills.
1512        This works well with MPEG-2 where N==12 or so, but for MPEG-4 it's a
1513        little slow...
1514    */
1515      const float vbvsize = (float)rc->param.vbvsize/8.f;
1516      const float vbvinitial = (float)rc->param.vbvinitial/8.f;
1517    
1518      const float maxrate = 0.9*rc->param.vbv_maxrate;
1519      const float vbvlow = 0.10f*vbvsize;
1520      const float r0 = (int)(maxrate/fps+0.5)/8.f;
1521    
1522      int i,k,l,n,violation = 0;
1523      float *scenefactor;
1524      int *scenestart;
1525      int *scenelength;
1526    
1527    /* first step: determine how many "scenes" there are and store their boundaries
1528       we could get all this from existing keyframe_positions, somehow, but there we
1529       don't have a min_scenelength, and it's no big deal to get it again.  */
1530    
1531      const int min_scenelength = 50;
1532      int num_scenes = 0;
1533      int last_scene = -999;
1534      for (i=0; i<rc->num_frames; i++) {
1535        if ( (rc->stats[i].type == XVID_TYPE_IVOP) && (i-last_scene>min_scenelength) )
1536        {
1537          last_scene = i;
1538          num_scenes++;
1539        }
1540      }
1541    
1542      scenefactor = (float*)malloc( num_scenes*sizeof(float) );
1543      scenestart = (int*)malloc( num_scenes*sizeof(int) );
1544      scenelength = (int*)malloc( num_scenes*sizeof(int) );
1545    
1546      if ((!scenefactor) || (!scenestart) || (!scenelength) )
1547      {
1548        free(scenefactor);
1549        free(scenestart);
1550        free(scenelength);
1551        /* remember: free(0) is valid and does exactly nothing. */
1552        return -1;
1553      }
1554    
1555    /* count again and safe the length/position */
1556    
1557      num_scenes = 0;
1558      last_scene = -999;
1559      for (i=0; i<rc->num_frames; i++) {
1560        if ( (rc->stats[i].type == XVID_TYPE_IVOP) && (i-last_scene>min_scenelength) )
1561        {
1562          if (num_scenes>0)
1563            scenelength[num_scenes-1]=i-last_scene;
1564          scenestart[num_scenes]=i;
1565          num_scenes++;
1566          last_scene = i;
1567        }
1568      }
1569      scenelength[num_scenes-1]=i-last_scene;
1570    
1571    /* second step: check for each scene, how much we can scale its frames up or down
1572       such that the VBV restriction is just fulfilled
1573    */
1574    
1575    
1576    #define R(k,n) (((n)+1-(k))*r0)     /* how much enters the buffer between frame k and n */
1577      for (l=0; l<num_scenes;l++)
1578      {
1579        const int start = scenestart[l];
1580        const int length = scenelength[l];
1581        twopass_stat_t * frames = &rc->stats[start];
1582    
1583        float S0n,Skn;
1584        float f,minf = 99999.f;
1585    
1586        S0n=0.;
1587        for (n=0;n<=length-1;n++)
1588        {
1589          S0n += frames[n].scaled_length;
1590    
1591          k=0;
1592          Skn = S0n;
1593          f = (R(k,n-1) + (vbvinitial - vbvlow)) / Skn;
1594          if (f < minf)
1595            minf = f;
1596    
1597          for (k=1;k<=n;k++)
1598          {
1599            Skn -= frames[k].scaled_length;
1600    
1601            f = (R(k,n-1) + (vbvsize - vbvlow)) / Skn;
1602            if (f < minf)
1603              minf = f;
1604          }
1605        }
1606    
1607        /* special case: at the end, fill buffer up to vbvinitial again
1608           TODO: Allow other values for buffer fill between scenes
1609           e.g. if n=N is smallest f-value, then check for better value */
1610    
1611        n=length;
1612        k=0;
1613        Skn = S0n;
1614        f = R(k,n-1)/Skn;
1615        if (f < minf)
1616          minf = f;
1617    
1618        for (k=1;k<=n-1;k++)
1619        {
1620          Skn -= frames[k].scaled_length;
1621    
1622          f = (R(k,n-1) + (vbvinitial - vbvlow)) / Skn;
1623          if (f < minf)
1624            minf = f;
1625        }
1626    
1627    #ifdef VBV_DEBUG
1628        printf("Scene %d (Frames %d-%d): VBVfactor %f\n", l, start, start+length-1 , minf);
1629    #endif
1630    
1631        scenefactor[l] = minf;
1632      }
1633    #undef R
1634    
1635    /* last step: now we know of any scene how much it can be scaled up or down without
1636       violating VBV. Next, distribute bits from the evil scenes to the good ones */
1637    
1638      do
1639      {
1640        float S_red = 0.f;    /* how much to redistribute */
1641        float S_elig = 0.f;   /* sum of bit for those scenes you can still swallow something*/
1642        int l;
1643    
1644        for (l=0;l<num_scenes;l++)   /* check how much is wrong */
1645        {
1646        const int start = scenestart[l];
1647        const int length = scenelength[l];
1648        twopass_stat_t * frames = &rc->stats[start];
1649    
1650          if (scenefactor[l] == 1.) /* exactly 1 means "don't touch this anymore!" */
1651            continue;
1652    
1653          if (scenefactor[l] > 1.) /* within limits */
1654          {
1655            for (n= 0; n < length; n++)
1656              S_elig += frames[n].scaled_length;
1657          }
1658          else /* underflowing segment */
1659          {
1660            for (n= 0; n < length; n++)
1661            {
1662              float newbytes = (float)frames[n].scaled_length * scenefactor[l];
1663              S_red += (float)frames[n].scaled_length - (float)newbytes;
1664              frames[n].scaled_length =(int)newbytes;
1665            }
1666            scenefactor[l] = 1.f;
1667          }
1668        }
1669    
1670        if (S_red < 1.f)   /* no more underflows */
1671          break;
1672    
1673        if (S_elig < 1.f)
1674        {
1675    #ifdef VBV_DEBUG
1676          fprintf(stderr,"Everything underflowing. \n");
1677    #endif
1678          free(scenefactor);
1679          free(scenestart);
1680          free(scenelength);
1681          return -2;
1682        }
1683    
1684        const float f_red = (1.f + S_red/S_elig);
1685    
1686    #ifdef VBV_DEBUG
1687        printf("Moving %.0f kB to avoid buffer underflow, correction factor: %.5f\n",S_red/1024.f,f_red);
1688    #endif
1689    
1690        violation=0;
1691        for (l=0; l<num_scenes; l++)   /* scale remaining scenes up to meet total size */
1692        {
1693          const int start = scenestart[l];
1694          const int length = scenelength[l];
1695          twopass_stat_t * frames = &rc->stats[start];
1696    
1697          if (scenefactor[l] == 1.)
1698            continue;
1699    
1700          /* there shouldn't be any segments with factor<1 left, so all the rest is >1 */
1701    
1702          for (n= 0; n < length; n++)
1703          {
1704            frames[n].scaled_length = (int)(frames[n].scaled_length * f_red + 0.5);
1705          }
1706    
1707          scenefactor[l] /= f_red;
1708          if (scenefactor[l] < 1.f)
1709            violation=1;
1710        }
1711    
1712      } while (violation);
1713    
1714      free(scenefactor);
1715      free(scenestart);
1716      free(scenelength);
1717      return 0;
1718    }
1719    
1720    
1721    #endif
1722    
1723    
1724  /*****************************************************************************  /*****************************************************************************
1725   * Still more low level stuff (nothing to do with stats treatment)   * Still more low level stuff (nothing to do with stats treatment)
1726   ****************************************************************************/   ****************************************************************************/

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