utils/wvrateadjust.cc

   1 /*
   2  * Worldvisions Weaver Software:
   3  *   Copyright (C) 1997-2002 Net Integration Technologies, Inc.
   4  *
   5  * WvRateAdjust is a WvEncoder that makes sure data comes out of it at a
   6  * given average rate.
   7  *
   8  * See wvrateadjust.h.
   9  */
  10 #include "wvrateadjust.h"
  11
  12 WvRateAdjust::WvRateAdjust(int _sampsize, int _irate_base, int _orate)
  13 #if 0
  14     : log("RateAdj", WvLog::Debug5)
  15 #endif
  16 {
  17     orate_n = _orate;
  18     orate_d = 1;
  19     match_rate = NULL;
  20
  21     init(_sampsize, _irate_base);
  22 }
  23
  24
  25 WvRateAdjust::WvRateAdjust(int _sampsize, int _irate_base,
  26                            WvRateAdjust *_match_rate)
  27 #if 0
  28     : log("RateAdj", WvLog::Debug5)
  29 #endif
  30 {
  31     match_rate = _match_rate;
  32     assert(match_rate);
  33
  34     orate_n = match_rate->irate_n;
  35     orate_d = match_rate->irate_d;
  36
  37     init(_sampsize, _irate_base);
  38 }
  39
  40
  41 void WvRateAdjust::init(int _sampsize, int _irate_base)
  42 {
  43     sampsize = _sampsize;
  44     irate_n = _irate_base * 10;
  45     irate_d = 10;
  46     epoch = wvtime();
  47     epoch.tv_sec--;
  48     bucket = 0;
  49 }
  50
  51
  52 // we always use all input samples and produce an appropriate number of
  53 // output samples.
  54 bool WvRateAdjust::_encode(WvBuf &inbuf, WvBuf &outbuf, bool flush)
  55 {
  56     if (!inbuf.used()) return true;
  57     assert((inbuf.used() % sampsize) == 0); // can't deal with partial samples
  58
  59     WvTime now = wvtime();
  60     unsigned isamps = inbuf.used() / sampsize;
  61
  62     // match our output rate to another stream's input rate, if requested
  63     if (match_rate)
  64     {
  65         orate_n = match_rate->irate_n;
  66         orate_d = match_rate->irate_d;
  67     }
  68
  69     // adjust the input rate estimate
  70     if (!epoch.tv_sec)
  71         epoch = now;
  72     irate_n += isamps * 10;
  73     irate_d = msecdiff(wvtime(), epoch) / 100;
  74     if (!irate_d)
  75         irate_d = 1;
  76
  77 #if 0
  78     log("irate=%s (%s/%s), orate=%s (%s/%s), bucket=%s\n",
  79         getirate(), irate_n, irate_d, getorate(), orate_n, orate_d,
  80         bucket);
  81 #endif
  82
  83     // reduce the rate estimate if it's getting out of control FIXME:
  84     // this method is (almost) unbearably cheesy because it's very
  85     // "blocky" - it doesn't happen every time, so it'll cause sudden
  86     // jumps from one value to the next.  Hopefully not a big deal,
  87     // since the input rate is supposed to be constant anyway.  The
  88     // hardcoded constants are also rather weird.
  89     if (irate_d > 100) // ten seconds
  90     {
  91         epoch.tv_sec++; // time now starts one second later
  92         irate_n = irate_n * (irate_d - 10)/irate_d;
  93         irate_d -= 10;
  94
  95 #if 0
  96         log("  JUMP!  new irate=%s (%s/%s)\n", getirate(), irate_n, irate_d);
  97 #endif
  98     }
  99
 100     int plus = orate_n * irate_d, minus = irate_n * orate_d;
 101     //log("plus=%s, minus=%s, ", plus, minus);
 102
 103     unsigned omax = isamps + isamps/2;
 104     //log("isamps=%s, omax=%s\n", isamps, omax);
 105
 106     const unsigned char *iptr = inbuf.get(isamps * sampsize);
 107     unsigned char *ostart, *optr;
 108
 109     ostart = optr = outbuf.alloc(omax * sampsize);
 110
 111     // copy the buffers using the "Bresenham line-drawing" algorithm.
 112     for (unsigned s = 0; s < isamps; s++, iptr += sampsize)
 113     {
 114         bucket += plus;
 115         //log("s=%s, bucket=%s (+%s, -%s)\n", s, bucket, plus, minus);
 116
 117         while (bucket >= minus)
 118         {
 119             // allocate more buffer space if needed
 120             if ((unsigned)(optr - ostart) >= omax * sampsize)
 121                 ostart = optr = outbuf.alloc(omax * sampsize);
 122
 123             for (int i = 0; i < sampsize; i++)
 124                 optr[i] = iptr[i];
 125             optr += sampsize;
 126             bucket -= minus;
 127         }
 128     }
 129
 130     unsigned un = omax*sampsize - (optr - ostart);
 131     //log("unalloc %s/%s (%s)\n", un, omax*sampsize, optr-ostart);
 132     outbuf.unalloc(un);
 133
 134     return true;
 135 }
 136
 137