mpeg2enc/ratectl.c

   1 /* ratectl.c, bitrate control routines (linear quantization only currently) */
   2
   3 /* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */
   4
   5 /*
   6  * Disclaimer of Warranty
   7  *
   8  * These software programs are available to the user without any license fee or
   9  * royalty on an "as is" basis.  The MPEG Software Simulation Group disclaims
  10  * any and all warranties, whether express, implied, or statuary, including any
  11  * implied warranties or merchantability or of fitness for a particular
  12  * purpose.  In no event shall the copyright-holder be liable for any
  13  * incidental, punitive, or consequential damages of any kind whatsoever
  14  * arising from the use of these programs.
  15  *
  16  * This disclaimer of warranty extends to the user of these programs and user's
  17  * customers, employees, agents, transferees, successors, and assigns.
  18  *
  19  * The MPEG Software Simulation Group does not represent or warrant that the
  20  * programs furnished hereunder are free of infringement of any third-party
  21  * patents.
  22  *
  23  * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware,
  24  * are subject to royalty fees to patent holders.  Many of these patents are
  25  * general enough such that they are unavoidable regardless of implementation
  26  * design.
  27  *
  28  */
  29
  30 #include <stdio.h>
  31 #include <limits.h>
  32 #include <math.h>
  33 #include <pthread.h>
  34
  35 #include "config.h"
  36 #include "global.h"
  37 #include "fastintfns.h"
  38
  39 /* rate control variables */
  40 /*
  41  * static double R, T, d;
  42  * static double actsum;
  43  * static int Np, Nb;
  44  * static double S, Q;
  45  * static int prev_mquant;
  46  * static double bitcnt_EOP;
  47  * static double next_ip_delay; // due to frame reordering delay
  48  * static double decoding_time;
  49  * static int Xi, Xp, Xb, r, d0i, d0p, d0b;
  50  * static double avg_act;
  51  */
  52
  53 void ratectl_init_seq(ratectl_t *ratectl)
  54 {
  55         pthread_mutexattr_t mutex_attr;
  56         pthread_mutexattr_init(&mutex_attr);
  57         pthread_mutex_init(&(ratectl->ratectl_lock), &mutex_attr);
  58
  59         ratectl->avg_KI = 2.5;   /* TODO: These values empirically determined            */
  60         ratectl->avg_KB = 10.0;   /* for MPEG-1, may need tuning for MPEG-2   */
  61         ratectl->avg_KP = 10.0;
  62
  63         ratectl->bits_per_mb = (double)bit_rate / (mb_per_pict);
  64         /* reaction parameter (constant) decreased to increase response
  65            rate as encoder is currently tending to under/over-shoot... in
  66            rate TODO: Reaction parameter is *same* for every frame type
  67            despite different weightings...  */
  68
  69         if (ratectl->r == 0)
  70                 ratectl->r = (int)floor(2.0 * bit_rate / frame_rate + 0.5);
  71
  72         ratectl->Ki = 1.2;  /* EXPERIMENT: ADJUST activities for I MB's */
  73         ratectl->Kb = 1.4;
  74         ratectl->Kp = 1.1;
  75
  76 /* average activity */
  77         if (ratectl->avg_act == 0.0)  ratectl->avg_act = 400.0;
  78
  79 /* remaining # of bits in GOP */
  80         ratectl->R = 0;
  81         ratectl->IR = 0;
  82
  83         /* Heuristic: In constant bit-rate streams we assume buffering
  84            will allow us to pre-load some (probably small) fraction of the
  85            buffers size worth of following data if earlier data was
  86            undershot its bit-rate allocation
  87
  88         */
  89
  90         ratectl->CarryR = 0;
  91         ratectl->CarryRLim = video_buffer_size / 3;
  92         /* global complexity (Chi! not X!) measure of different frame types */
  93         /* These are just some sort-of sensible initial values for start-up */
  94
  95         ratectl->Xi = 1500*mb_per_pict;   /* Empirically derived values */
  96         ratectl->Xp = 550*mb_per_pict;
  97         ratectl->Xb = 170*mb_per_pict;
  98         ratectl->d0i = -1;                              /* Force initial Quant prediction */
  99         ratectl->d0pb = -1;
 100
 101         ratectl->current_quant = 1;
 102 }
 103
 104 void ratectl_init_GOP(ratectl_t *ratectl, int np, int nb)
 105 {
 106         double per_gop_bits =
 107                 (double)(1 + np + nb) * (double)bit_rate / frame_rate;
 108
 109         /* A.Stevens Aug 2000: at last I've found the wretched
 110            rate-control overshoot bug...  Simply "topping up" R here means
 111            that we can accumulate an indefinately large pool of bits
 112            "saved" from previous low-activity frames.  This is of
 113            course nonsense.
 114
 115            In CBR we can only accumulate as much as our buffer allows, after that
 116            the eventual system stream will have to be padded.  The automatic padding
 117            will make this calculation fairly reasonable but since that's based on
 118            estimates we again impose our rough and ready heuristic that we can't
 119            accumulate more than approximately half  a video buffer full.
 120
 121            In VBR we actually do nothing different.  Here the bitrate is
 122            simply a ceiling rate which we expect to undershoot a lot as
 123            our quantisation floor cuts in. We specify a great big buffer
 124            and simply don't pad when we undershoot.
 125
 126            However, we don't want to carry over absurd undershoots as when it
 127            does get hectic we'll breach our maximum.
 128
 129            TODO: For CBR we should do a proper video buffer model and use
 130            it to make bit allocation decisions.
 131
 132         */
 133
 134         if( ratectl->R > 0  )
 135         {
 136                 /* We replacing running estimate of undershoot with
 137                    *exact* value and use that for calculating how much we
 138                    may "carry over"
 139                 */
 140                 ratectl->gop_undershoot = intmin( video_buffer_size/2, (int)ratectl->R );
 141
 142                 ratectl->R = ratectl->gop_undershoot + per_gop_bits;
 143         }
 144         else
 145         {
 146                 /* Overshoots are easy - we have to make up the bits */
 147                 ratectl->R +=  per_gop_bits;
 148                 ratectl->gop_undershoot = 0;
 149         }
 150         ratectl->IR = ratectl->R;
 151         ratectl->Np = fieldpic ? 2 * np + 1 : np;
 152         ratectl->Nb = fieldpic ? 2 * nb : nb;
 153 }
 154
 155 static int scale_quant(pict_data_s *picture, double quant )
 156 {
 157         int iquant;
 158
 159         if (picture->q_scale_type  )
 160         {
 161                 iquant = (int) floor(quant+0.5);
 162
 163                 /* clip mquant to legal (linear) range */
 164                 if (iquant<1)
 165                         iquant = 1;
 166                 if (iquant>112)
 167                         iquant = 112;
 168
 169                 iquant =
 170                         non_linear_mquant_table[map_non_linear_mquant[iquant]];
 171         }
 172         else
 173         {
 174                 /* clip mquant to legal (linear) range */
 175                 iquant = (int)floor(quant+0.5);
 176                 if (iquant<2)
 177                         iquant = 2;
 178                 if (iquant>62)
 179                         iquant = 62;
 180                 iquant = (iquant/2)*2; // Must be *even*
 181         }
 182         return iquant;
 183 }
 184
 185
 186
 187
 188 /* compute variance of 8x8 block */
 189 static double var_sblk(p, lx)
 190 unsigned char *p;
 191 int lx;
 192 {
 193         int j;
 194         register unsigned int v, s, s2;
 195
 196         s = s2 = 0;
 197
 198         for (j=0; j<8; j++)
 199         {
 200                 v = p[0];   s += v;    s2 += v * v;
 201                 v = p[1];   s += v;    s2 += v * v;
 202                 v = p[2];   s += v;    s2 += v * v;
 203                 v = p[3];   s += v;    s2 += v * v;
 204                 v = p[4];   s += v;    s2 += v * v;
 205                 v = p[5];   s += v;    s2 += v * v;
 206                 v = p[6];   s += v;    s2 += v * v;
 207                 v = p[7];   s += v;    s2 += v * v;
 208                 p += lx;
 209         }
 210
 211         return (double)s2 / 64.0 - ((double)s / 64.0) * ((double)s / 64.0);
 212 }
 213
 214
 215 static double calc_actj(pict_data_s *picture)
 216 {
 217         int i,j,k,l;
 218         double actj,sum;
 219         uint16_t *i_q_mat;
 220         int actsum;
 221         sum = 0.0;
 222         k = 0;
 223
 224         for (j=0; j<height2; j+=16)
 225                 for (i=0; i<width; i+=16)
 226                 {
 227                         /* A.Stevens Jul 2000 Luminance variance *has* to be a rotten measure
 228                            of how active a block in terms of bits needed to code a lossless DCT.
 229                            E.g. a half-white half-black block has a maximal variance but
 230                            pretty small DCT coefficients.
 231
 232                            So.... we use the absolute sum of DCT coefficients as our
 233                            variance measure.
 234                         */
 235                         if( picture->mbinfo[k].mb_type  & MB_INTRA )
 236                         {
 237                                 i_q_mat = i_intra_q;
 238                                 /* EXPERIMENT: See what happens if we compensate for
 239                                  the wholly disproprotionate weight of the DC
 240                                  coefficients.  Shold produce more sensible results...  */
 241                                 actsum =  -80*COEFFSUM_SCALE;
 242                         }
 243                         else
 244                         {
 245                                 i_q_mat = i_inter_q;
 246                                 actsum = 0;
 247                         }
 248
 249                         /* It takes some bits to code even an entirely zero block...
 250                            It also makes a lot of calculations a lot better conditioned
 251                            if it can be guaranteed that activity is always distinctly
 252                            non-zero.
 253                          */
 254
 255
 256                         for( l = 0; l < 6; ++l )
 257                                 actsum +=
 258                                         (*pquant_weight_coeff_sum)
 259                                             ( cur_picture.mbinfo[k].dctblocks[l], i_q_mat ) ;
 260                         actj = (double)actsum / (double)COEFFSUM_SCALE;
 261                         if( actj < 12.0 )
 262                                 actj = 12.0;
 263
 264                         picture->mbinfo[k].act = (double)actj;
 265                         sum += (double)actj;
 266                         ++k;
 267                 }
 268         return sum;
 269 }
 270
 271 /* Note: we need to substitute K for the 1.4 and 1.0 constants -- this can
 272    be modified to fit image content */
 273
 274 /* Step 1: compute target bits for current picture being coded */
 275 void ratectl_init_pict(ratectl_t *ratectl, pict_data_s *picture)
 276 {
 277         double avg_K;
 278         double target_Q;
 279         double current_Q;
 280         double Si, Sp, Sb;
 281         /* TODO: A.Stevens  Nov 2000 - This modification needs testing visually.
 282
 283            Weird.  The original code used the average activity of the
 284            *previous* frame as the basis for quantisation calculations for
 285            rather than the activity in the *current* frame.  That *has* to
 286            be a bad idea..., surely, here we try to be smarter by using the
 287            current values and keeping track of how much of the frames
 288            activitity has been covered as we go along.
 289
 290            We also guesstimate the relationship between  (sum
 291            of DCT coefficients) and actual quantisation weighted activty.
 292            We use this to try to predict the activity of each frame.
 293         */
 294
 295         ratectl->actsum =  calc_actj(picture );
 296         ratectl->avg_act = (double)ratectl->actsum/(double)(mb_per_pict);
 297         ratectl->sum_avg_act += ratectl->avg_act;
 298         ratectl->actcovered = 0.0;
 299
 300         /* Allocate target bits for frame based on frames numbers in GOP
 301            weighted by global complexity estimates and B-frame scale factor
 302            T = (Nx * Xx/Kx) / Sigma_j (Nj * Xj / Kj)
 303         */
 304         ratectl->min_q = ratectl->min_d = INT_MAX;
 305         ratectl->max_q = ratectl->max_d = INT_MIN;
 306         switch (picture->pict_type)
 307         {
 308         case I_TYPE:
 309
 310                 /* There is little reason to rely on the *last* I-frame
 311                    as they're not closely related.  The slow correction of
 312                    K should be enough to fine-tune...
 313                 */
 314
 315                 ratectl->d = ratectl->d0i;
 316                 avg_K = ratectl->avg_KI;
 317                 Si = (ratectl->Xi + 3.0*avg_K*ratectl->actsum)/4.0;
 318                 ratectl->T = ratectl->R/(1.0+ratectl->Np*ratectl->Xp*ratectl->Ki/(Si*ratectl->Kp)+ratectl->Nb*ratectl->Xb*ratectl->Ki/(Si*ratectl->Kb));
 319
 320                 break;
 321         case P_TYPE:
 322                 ratectl->d = ratectl->d0pb;
 323                 avg_K = ratectl->avg_KP;
 324                 Sp = (ratectl->Xp + avg_K*ratectl->actsum) / 2.0;
 325                 ratectl->T =  ratectl->R/(ratectl->Np+ratectl->Nb*ratectl->Kp*ratectl->Xb/(ratectl->Kb*Sp)) + 0.5;
 326                 break;
 327         case B_TYPE:
 328                 ratectl->d = ratectl->d0pb;            // I and P frame share ratectl virtual buffer
 329                 avg_K = ratectl->avg_KB;
 330                 Sb = ratectl->Xb /* + avg_K * ratectl->actsum) / 2.0 */;
 331                 ratectl->T =  ratectl->R/(ratectl->Nb+ratectl->Np*ratectl->Kb*ratectl->Xp/(ratectl->Kp*Sb));
 332                 break;
 333         }
 334
 335         /* Undershot bits have been "returned" via R */
 336         if( ratectl->d < 0 )
 337                 ratectl->d = 0;
 338
 339         /* We don't let the target volume get absurdly low as it makes some
 340            of the prediction maths ill-condtioned.  At these levels quantisation
 341            is always minimum anyway
 342         */
 343         if( ratectl->T < 4000.0 )
 344         {
 345                 ratectl->T = 4000.0;
 346         }
 347         target_Q = scale_quant(picture,
 348                                                    avg_K * ratectl->avg_act *(mb_per_pict) / ratectl->T);
 349         current_Q = scale_quant(picture,62.0*ratectl->d / ratectl->r);
 350 #ifdef DEBUG
 351         if( !quiet )
 352         {
 353                 /* printf( "AA=%3.4f T=%6.0f K=%.1f ",avg_act, (double)T, avg_K  ); */
 354                 printf( "AA=%3.4f SA==%3.4f ",avg_act, sum_avg_act  );
 355         }
 356 #endif
 357
 358         if ( current_Q < 3 && target_Q > 12 )
 359         {
 360                 /* We're undershooting and a serious surge in the data_flow
 361                    due to lagging adjustment is possible...
 362                 */
 363                 ratectl->d = (int) (target_Q * ratectl->r / 62.0);
 364         }
 365
 366         ratectl->S = bitcount();
 367         ratectl->frame_start = bitcount();
 368 //      ratectl->current_quant = ratectl->d * 62.0 / ratectl->r;
 369         if(ratectl->current_quant < 1) ratectl->current_quant = 1;
 370         if(ratectl->current_quant > 100) ratectl->current_quant = 100;
 371 }
 372
 373 /* compute initial quantization stepsize (at the beginning of picture) */
 374 int ratectl_start_mb(ratectl_t *ratectl, pict_data_s *picture)
 375 {
 376         double Qj;
 377         int mquant;
 378
 379         if(fixed_mquant)
 380                 Qj = fixed_mquant;
 381         else
 382                 Qj = ratectl->current_quant;
 383 //              Qj = ratectl->d * 62.0 / ratectl->r;
 384
 385         mquant = scale_quant( picture, Qj);
 386         mquant = intmax(mquant, quant_floor);
 387
 388         return mquant;
 389 }
 390
 391 void ratectl_update_pict(ratectl_t *ratectl, pict_data_s *picture)
 392 {
 393         double X;
 394         double K;
 395         int64_t AP,PP;          /* Actual and padded picture bit counts */
 396         int    i;
 397         int    Qsum;
 398         int frame_overshoot;
 399         double avg_bitrate;
 400         int last_size;
 401         double new_weight;
 402         double old_weight;
 403
 404         if(fixed_mquant) return;
 405
 406         AP = bitcount() - ratectl->S;
 407         frame_overshoot = (int)AP-(int)ratectl->T;
 408
 409         /* For the virtual buffers for quantisation feedback it is the
 410            actual under/overshoot that counts, not what's left after padding
 411         */
 412         ratectl->d += frame_overshoot;
 413
 414         /* If the cummulative undershoot is getting too large (as
 415            a rough and ready heuristic we use 1/2 video buffer size)
 416            we start padding the stream.  Or, in the case of VBR,
 417            we pretend we're padding but don't actually write anything!
 418
 419          */
 420
 421         if( ratectl->gop_undershoot-frame_overshoot > video_buffer_size/2 )
 422         {
 423                 int padding_bytes =
 424                         ((ratectl->gop_undershoot - frame_overshoot) - video_buffer_size/2)/8;
 425                 if( quant_floor != 0 )  /* VBR case pretend to pad */
 426                 {
 427                         PP = AP + padding_bytes;
 428                 }
 429                 else
 430                 {
 431 //                      printf( "PAD" );
 432 //                      alignbits();
 433                         for( i = 0; i < padding_bytes/2; ++i )
 434                         {
 435 //                              putbits(0, 16);
 436                         }
 437                         PP = bitcount() - ratectl->S;                   /* total # of bits in picture */
 438                 }
 439                 frame_overshoot = (int)PP - (int)ratectl->T;
 440         }
 441         else
 442                 PP = AP;
 443
 444         /* Estimate cummulative undershoot within this gop.
 445            This is only an estimate because T includes an allocation
 446            from earlier undershoots causing multiple counting.
 447            Padding and an exact calculation each gop prevent the error
 448            in the estimate growing too excessive...
 449            */
 450         ratectl->gop_undershoot -= frame_overshoot;
 451         ratectl->gop_undershoot = ratectl->gop_undershoot > 0 ? ratectl->gop_undershoot : 0;
 452         ratectl->R -= PP;                                               /* remaining # of bits in GOP */
 453
 454         Qsum = 0;
 455         for( i = 0; i < mb_per_pict; ++i )
 456         {
 457                 Qsum += picture->mbinfo[i].mquant;
 458         }
 459
 460
 461         ratectl->AQ = (double)Qsum/(double)mb_per_pict;
 462         /* TODO: The X are used as relative activity measures... so why
 463            bother dividing by 2?
 464            Note we have to be careful to measure the actual data not the
 465            padding too!
 466         */
 467         ratectl->SQ += ratectl->AQ;
 468         X = (double)AP*(ratectl->AQ/2.0);
 469
 470         K = X / ratectl->actsum;
 471 #ifdef DEBUG
 472         if( !quiet )
 473         {
 474                 printf( "AQ=%.1f SQ=%.2f",  AQ,SQ);
 475         }
 476 #endif
 477         /* Bits that never got used in the past can't be resurrected
 478            now...  We use an average of past (positive) virtual buffer
 479            fullness in the event of an under-shoot as otherwise we will
 480            tend to over-shoot heavily when activity picks up.
 481
 482            TODO: We should really use our estimate K[IBP] of
 483            bit_usage*activity / quantisation ratio to set a "sensible"
 484            initial d to achieve a reasonable initial quantisation. Rather
 485            than have to cut in a huge (lagging correction).
 486
 487            Alternatively, simply requantising with mean buffer if there is
 488            a big buffer swing would work nicely...
 489
 490         */
 491
 492         /* EXPERIMENT: Xi are used as a guesstimate of likely *future* frame
 493            activities based on the past.  Thus we don't want anomalous outliers
 494            due to scene changes swinging things too much.  Introduce moving averages
 495            for the Xi...
 496            TODO: The averaging constants should be adjust to suit relative frame
 497            frequencies...
 498         */
 499         switch (picture->pict_type)
 500         {
 501         case I_TYPE:
 502                 ratectl->avg_KI = (K + ratectl->avg_KI * K_AVG_WINDOW_I) / (K_AVG_WINDOW_I+1.0) ;
 503                 ratectl->d0i = ratectl->d;
 504                 ratectl->Xi = (X + 3.0 * ratectl->Xi) / 4.0;
 505                 break;
 506         case P_TYPE:
 507                 ratectl->avg_KP = (K + ratectl->avg_KP * K_AVG_WINDOW_P) / (K_AVG_WINDOW_P+1.0) ;
 508                 ratectl->d0pb = ratectl->d;
 509                 ratectl->Xp = (X + ratectl->Xp * 12.0) / 13.0;
 510                 ratectl->Np--;
 511                 break;
 512         case B_TYPE:
 513                 ratectl->avg_KB = (K + ratectl->avg_KB * K_AVG_WINDOW_B) / (K_AVG_WINDOW_B + 1.0) ;
 514                 ratectl->d0pb = ratectl->d;
 515                 ratectl->Xb = (X + ratectl->Xb * 24.0) / 25.0;
 516                 ratectl->Nb--;
 517                 break;
 518         }
 519
 520         ratectl->frame_end = bitcount();
 521
 522         last_size = ratectl->frame_end - ratectl->frame_start;
 523         avg_bitrate = (double)last_size * frame_rate;
 524         switch(picture->pict_type)
 525         {
 526                 case I_TYPE:
 527                         new_weight = avg_bitrate / bit_rate * 1 / N;
 528                         old_weight = (double)(N - 1) / N;
 529                         break;
 530
 531                 default:
 532                 case P_TYPE:
 533                         new_weight = avg_bitrate / bit_rate * (N - 1) / N;
 534                         old_weight = (double)1 / N;
 535                         break;
 536         }
 537         ratectl->current_quant *= (old_weight + new_weight);
 538
 539 /*
 540  * printf("ratectl_update_pict %f %f\n",
 541  *      avg_bitrate,
 542  *      ratectl->current_quant);
 543  */
 544
 545 }
 546
 547 /* Step 2: measure virtual buffer - estimated buffer discrepancy */
 548 int ratectl_calc_mquant(ratectl_t *ratectl, pict_data_s *picture, int j)
 549 {
 550         int mquant;
 551         double dj, Qj, actj, N_actj;
 552
 553 //      pthread_mutex_lock(&(ratectl->ratectl_lock));
 554         /* A.Stevens 2000 : we measure how much *information* (total activity)
 555            has been covered and aim to release bits in proportion.  Indeed,
 556            complex blocks get an disproprortionate boost of allocated bits.
 557            To avoid visible "ringing" effects...
 558
 559         */
 560
 561         actj = picture->mbinfo[j].act;
 562         /* Guesstimate a virtual buffer fullness based on
 563            bits used vs. bits in proportion to activity encoded
 564         */
 565
 566
 567         dj = ((double)ratectl->d) +
 568                 ((double)(bitcount() - ratectl->S) - ratectl->actcovered * ((double)ratectl->T) / ratectl->actsum);
 569
 570
 571
 572         /* scale against dynamic range of mquant and the bits/picture count.
 573            quant_floor != 0.0 is the VBR case where we set a bitrate as a (high)
 574            maximum and then put a floor on quantisation to achieve a reasonable
 575            overall size.
 576            Not that this *is* baseline quantisation.  Not adjust for local activity.
 577            Otherwise we end up blurring active macroblocks. Silly in a VBR context.
 578         */
 579
 580         Qj = dj * 62.0 / ratectl->r;
 581
 582 //printf("ratectl_calc_mquant %f\n", Qj);
 583         if(fixed_mquant)
 584                 Qj = fixed_mquant;
 585         else
 586                 Qj = ratectl->current_quant;
 587
 588         Qj = (Qj > quant_floor) ? Qj : quant_floor;
 589         /*  Heuristic: Decrease quantisation for blocks with lots of
 590                 sizeable coefficients.  We assume we just get a mess if
 591                 a complex texture's coefficients get chopped...
 592         */
 593
 594         N_actj =  actj < ratectl->avg_act ?
 595                 1.0 :
 596                 (actj + act_boost * ratectl->avg_act) /
 597                 (act_boost * actj + ratectl->avg_act);
 598
 599         mquant = scale_quant(picture, Qj * N_actj);
 600
 601
 602         /* Update activity covered */
 603
 604         ratectl->actcovered += actj;
 605 //      pthread_mutex_unlock(&(ratectl->ratectl_lock));
 606
 607         return mquant;
 608 }
 609
 610 /* VBV calculations
 611  *
 612  * generates warnings if underflow or overflow occurs
 613  */
 614
 615 /* vbv_end_of_picture
 616  *
 617  * - has to be called directly after writing picture_data()
 618  * - needed for accurate VBV buffer overflow calculation
 619  * - assumes there is no byte stuffing prior to the next start code
 620  */
 621
 622 void vbv_end_of_picture()
 623 {
 624 }
 625
 626 /* calc_vbv_delay
 627  *
 628  * has to be called directly after writing the picture start code, the
 629  * reference point for vbv_delay
 630  */
 631
 632 void calc_vbv_delay()
 633 {
 634 }
 635
 636 void stop_ratectl(ratectl_t *ratectl)
 637 {
 638         pthread_mutex_destroy(&(ratectl->ratectl_lock));
 639 }