vid_ratectrl.c

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/*
 *  NOTE: 
 * 
 *  I removed the OFFLINE_RATE_CONTROL stuff because I'm not using it.
 * 
 *  Brendan Dowling 8/27/96
 */

/************************************************************************
 *
 *  vid_ratectrl.c, part of tmn (TMN encoder)
 *  Copyright (C) 1995, 1996  Telenor R&D, Norway
 *        Karl Olav Lillevold <Karl.Lillevold@nta.no>
 *  
 *  Contacts: 
 *  Karl Olav Lillevold               <Karl.Lillevold@nta.no>, or
 *  Robert Danielsen                  <Robert.Danielsen@nta.no>
 *
 *  Telenor Research and Development  http://www.nta.no/brukere/DVC/
 *  P.O.Box 83                        tel.:   +47 63 84 84 00
 *  N-2007 Kjeller, Norway            fax.:   +47 63 81 00 76
 *  
 ************************************************************************/

/*
 * Disclaimer of Warranty
 *
 * These software programs are available to the user without any
 * license fee or royalty on an "as is" basis.  Telenor Research and
 * Development disclaims any and all warranties, whether express,
 * implied, or statuary, including any implied warranties or
 * merchantability or of fitness for a particular purpose.  In no
 * event shall the copyright-holder be liable for any incidental,
 * punitive, or consequential damages of any kind whatsoever arising
 * from the use of these programs.
 *
 * This disclaimer of warranty extends to the user of these programs
 * and user's customers, employees, agents, transferees, successors,
 * and assigns.
 *
 * Telenor Research and Development does not represent or warrant that
 * the programs furnished hereunder are free of infringement of any
 * third-party patents.
 *
 * Commercial implementations of H.263, including shareware, are
 * subject to royalty fees to patent holders.  Many of these patents
 * are general enough such that they are unavoidable regardless of
 * implementation design.
 * */


/* IMPORTANT NOTE: 
   
   The H.263 standard does not specify a rate control method.  Each
   H.263 encoder has to implement a rate control suited for what the
   encoder is going to be used for. This software now includes two
   rate control methods: (i) the rate control from the TMN5 document,
   and (ii) the rate control method used to encode the H.263
   bitstreams submitted to the MPEG-4 tests. The default rate control
   is (i) which is suitable for low-delay teleconferencing. If the
   software is compiled with the OFFLINE_RATE_CONTROL flag, (ii) will
   be used. Read more about (ii) below.
   
   */

#include "vid_sim.h"
#include "video_codec.h"

extern video_codec *VidSt;

/* 
 * These routines are needed for the low-delay , variable frame rate,
 * rate control specified in the TMN5 document
 */

#include <math.h>

#if(0)
/* rate control static variables */
static float B_prev;     /* number of bits spent for the previous frame */
static float B_target;   /* target number of bits/picture               */
static float global_adj; /* due to bits spent for the previous frame    */
#endif

void InitializeRateControl()
{
  (VidSt->B_prev) = (float)0.0;
}

void UpdateRateControl(int bits)
{
  (VidSt->B_prev) = (float)bits;
}

int InitializeQuantizer(int pict_type, float bit_rate, 
        float target_frame_rate, float QP_mean) 

/* QP_mean = mean quantizer parameter for the previous picture */
/* bitcount = current total bit count                          */
/* To calculate bitcount in vid_coder.c, do something like this :  */
/* int bitcount;                                               */
/* AddBitsPicture(bits);                                       */
/* bitcount = bits->total;                                     */

{
  int newQP;

  if (pict_type == PCT_INTER) {

    (VidSt->B_target) = bit_rate / target_frame_rate;

    /* compute picture buffer descrepency as of the previous picture */

    if ((VidSt->B_prev) != 0.0) {
      (VidSt->global_adj) = ((VidSt->B_prev) - (VidSt->B_target)) / (2*(VidSt->B_target));
    }
    else {
      (VidSt->global_adj) = (float)0.0;
    }
    newQP = (int)(QP_mean * (1 + (VidSt->global_adj)) + (float)0.5);
    newQP = mmax(1,mmin(31,newQP));  
  }
  else if (pict_type == PCT_INTRA) {
    fprintf(stderr,"No need to call InititializeQuantizer() for Intra picture\n");
    exit(-1);
  }
  else  {
    fprintf(stderr,"Error (InitializePictureRate): picture type unkown.\n");
    exit(-1);
  }  
#if 1
  printf("Global adj = %.2f\n", (VidSt->global_adj));
  printf("meanQP = %.2f   newQP = %d\n", QP_mean, newQP);
#endif
  fprintf(stdout,"Target no. of bits: %.2f\n", (VidSt->B_target));

  return newQP;
}


/*********************************************************************
*   Name:          UpdateQuantizer
*
*
* Description: This function generates a new quantizer step size based
*                  on bits spent up until current macroblock and bits
*                  spent from the previous picture.  Note: this
*                  routine should be called at the beginning of each
*                  macroblock line as specified by TMN4. However, this
*                  can be done at any macroblock if so desired.
*
*  Input: current macroblock number (raster scan), mean quantizer
*  paramter for previous picture, bit rate, source frame rate,
*  hor. number of macroblocks, vertical number of macroblocks, total #
*  of bits used until now in the current picture.
*
*  Returns: Returns a new quantizer step size for the use of current
*  macroblock Note: adjustment to fit with 2-bit DQUANT should be done
*  in the calling program.
*
*  Side Effects:  
*
*  Date: 1/5/95    Author: Anurag Bist
*
**********************************************************************/


int UpdateQuantizer(int mb, float QP_mean, int pict_type, float bit_rate, 
                    int mb_width, int mb_height, int bitcount) 

/* mb = macroblock index number */
/* QP_mean = mean quantizer parameter for the previous picture */
/* bitcount = total # of bits used until now in the current picture */

{
  int newQP=16;
  float local_adj, descrepency, projection;
  
  if (pict_type == PCT_INTRA) {
    newQP = 16;         /* Changed from newQP = 16;, BD 8/27/96 */
  }
  else if (pict_type == PCT_INTER) {
    /* compute expected buffer fullness */
    
    projection = mb * ((VidSt->B_target) / (mb_width*mb_height));
    
    /* measure descrepency between current fullness and projection */
    descrepency= (bitcount - projection);
    
    /* scale */
    
    local_adj = 12 * descrepency / bit_rate;
    
#if(0)
    printf("mb = %d\n",mb);
    printf("bit_count = %d projection = %.2f \n",bitcount,projection);
    printf("B_target = %.2f local_adj = %.2f \n",(VidSt->B_target),local_adj);
#endif
    
    newQP = (int)(QP_mean * (1 + (VidSt->global_adj) + local_adj) + 0.5);
    
  /* the update equation for newQP in TMN4 document section 3.7 */

  }
  else  {
    fprintf(stderr,"Error (UpdateQuantizer): picture type unkown.\n");
  }
  
#if(0)
  printf("mb = %d  newQP = %d \n",mb,newQP);
#endif 

  newQP = mmax(1,mmin(31,newQP));
  return newQP;
}

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