encoder_toplevel.c

mediastreamer2是开源的网络传输媒体流的库

  /* set up context of key frame sizes and distances for more local
     datarate control */
  for( i = 0 ; i < KEY_FRAME_CONTEXT ; i ++ ) {
    cpi->PriorKeyFrameSize[i] = cpi->Configuration.KeyFrameDataTarget;
    cpi->PriorKeyFrameDistance[i] = cpi->pb.info.keyframe_frequency_force;
  }

  /* Keep track of the total number of Key Frames Coded. */
  cpi->KeyFrameCount = 1;
  cpi->LastKeyFrame = 1;
  cpi->TotKeyFrameBytes = 0;

  /* A key frame is not a dropped frame there for reset the count of
     consequative dropped frames. */
  cpi->DropCount = 0;

  SetupKeyFrame(cpi);

  /* Calculate a new target rate per frame allowing for average key
     frame frequency and size thus far. */
  if ( cpi->Configuration.TargetBandwidth >
       ((cpi->Configuration.KeyFrameDataTarget *
         cpi->Configuration.OutputFrameRate)/
        cpi->pb.info.keyframe_frequency) ) {

    cpi->frame_target_rate =
      (ogg_int32_t)((cpi->Configuration.TargetBandwidth -
                     ((cpi->Configuration.KeyFrameDataTarget *
                       cpi->Configuration.OutputFrameRate)/
                      cpi->pb.info.keyframe_frequency)) /
                    cpi->Configuration.OutputFrameRate);
  }else
    cpi->frame_target_rate = 1;

  /* Set baseline frame target rate. */
  cpi->BaseLineFrameTargetRate = cpi->frame_target_rate;

  /* A key frame is not a dropped frame there for reset the count of
     consequative dropped frames. */
  cpi->DropCount = 0;

  /* Initialise drop frame trigger to 5 frames worth of data. */
  cpi->DropFrameTriggerBytes = cpi->frame_target_rate * DF_CANDIDATE_WINDOW;

  /* Set a target size for this key frame based upon the baseline
     target and frequency */
  cpi->ThisFrameTargetBytes = cpi->Configuration.KeyFrameDataTarget;

  /* Get a DCT quantizer level for the key frame. */
  cpi->MotionScore = cpi->pb.UnitFragments;

  RegulateQ(cpi, cpi->pb.UnitFragments);

  cpi->pb.LastFrameQualityValue = cpi->pb.ThisFrameQualityValue;

  /* Initialise quantizer. */
  UpdateQC(cpi, cpi->pb.ThisFrameQualityValue );

  /* Initialise the cpi->pb.display_fragments and other fragment
     structures for the first frame. */
  for ( i = 0; i < cpi->pb.UnitFragments; i ++ )
    cpi->FragmentLastQ[i] = cpi->pb.ThisFrameQualityValue;

  /* Compress and output the frist frame. */
  PickIntra( cpi,
             cpi->pb.YSBRows, cpi->pb.YSBCols);
  UpdateFrame(cpi);

  /* Initialise the carry over rate targeting variables. */
  cpi->CarryOver = 0;

}

static void CompressKeyFrame(CP_INSTANCE *cpi){
  ogg_uint32_t  i;

  /* Before we compress reset the carry over to the actual frame carry over */
  cpi->CarryOver = cpi->Configuration.TargetBandwidth * cpi->CurrentFrame  /
    cpi->Configuration.OutputFrameRate - cpi->TotalByteCount;

  /* Keep track of the total number of Key Frames Coded */
  cpi->KeyFrameCount += 1;

  /* A key frame is not a dropped frame there for reset the count of
     consequative dropped frames. */
  cpi->DropCount = 0;

  SetupKeyFrame(cpi);

  /* set a target size for this frame */
  cpi->ThisFrameTargetBytes = (ogg_int32_t) cpi->frame_target_rate +
    ( (cpi->Configuration.KeyFrameDataTarget - cpi->frame_target_rate) *
      cpi->LastKeyFrame / cpi->pb.info.keyframe_frequency_force );

  if ( cpi->ThisFrameTargetBytes > cpi->Configuration.KeyFrameDataTarget )
    cpi->ThisFrameTargetBytes = cpi->Configuration.KeyFrameDataTarget;

  /* Get a DCT quantizer level for the key frame. */
  cpi->MotionScore = cpi->pb.UnitFragments;

  RegulateQ(cpi, cpi->pb.UnitFragments);

  cpi->pb.LastFrameQualityValue = cpi->pb.ThisFrameQualityValue;

  /* Initialise DCT tables. */
  UpdateQC(cpi, cpi->pb.ThisFrameQualityValue );

  /* Initialise the cpi->pb.display_fragments and other fragment
     structures for the first frame. */
  for ( i = 0; i < cpi->pb.UnitFragments; i ++ )
    cpi->FragmentLastQ[i] = cpi->pb.ThisFrameQualityValue;


  /* Compress and output the frist frame. */
  PickIntra( cpi,
             cpi->pb.YSBRows, cpi->pb.YSBCols);
  UpdateFrame(cpi);

}

static void CompressFrame( CP_INSTANCE *cpi) {
  ogg_int32_t min_blocks_per_frame;
  ogg_uint32_t  i;
  int DropFrame = 0;
  ogg_uint32_t  ResidueBlocksAdded=0;
  ogg_uint32_t  KFIndicator = 0;

  double QModStep;
  double QModifier = 1.0;

  /* Clear down the macro block level mode and MV arrays. */
  for ( i = 0; i < cpi->pb.UnitFragments; i++ ) {
    cpi->pb.FragCodingMethod[i] = CODE_INTER_NO_MV;  /* Default coding mode */
    cpi->pb.FragMVect[i].x = 0;
    cpi->pb.FragMVect[i].y = 0;
  }

  /* Default to delta frames. */
  SetFrameType( &cpi->pb, DELTA_FRAME );

  /* Clear down the difference arrays for the current frame. */
  memset( cpi->pb.display_fragments, 0, cpi->pb.UnitFragments );
  memset( cpi->extra_fragments, 0, cpi->pb.UnitFragments );

  /* Calculate the target bytes for this frame. */
  cpi->ThisFrameTargetBytes = cpi->frame_target_rate;

  /* Correct target to try and compensate for any overall rate error
     that is developing */

  /* Set the max allowed Q for this frame based upon carry over
     history.  First set baseline worst Q for this frame */
  cpi->Configuration.ActiveMaxQ = cpi->Configuration.MaxQ + 10;
  if ( cpi->Configuration.ActiveMaxQ >= Q_TABLE_SIZE )
    cpi->Configuration.ActiveMaxQ = Q_TABLE_SIZE - 1;

  /* Make a further adjustment based upon the carry over and recent
   history..  cpi->Configuration.ActiveMaxQ reduced by 1 for each 1/2
   seconds worth of -ve carry over up to a limit of 6.  Also
   cpi->Configuration.ActiveMaxQ reduced if frame is a
   "DropFrameCandidate".  Remember that if we are behind the bit
   target carry over is -ve. */
  if ( cpi->CarryOver < 0 ) {
    if ( cpi->DropFrameCandidate ) {
      cpi->Configuration.ActiveMaxQ -= 4;
    }

    if ( cpi->CarryOver <
         -((ogg_int32_t)cpi->Configuration.TargetBandwidth*3) )
      cpi->Configuration.ActiveMaxQ -= 6;
    else
      cpi->Configuration.ActiveMaxQ +=
        (ogg_int32_t) ((cpi->CarryOver*2) /
                       (ogg_int32_t)cpi->Configuration.TargetBandwidth);

    /* Check that we have not dropped quality too far */
    if ( cpi->Configuration.ActiveMaxQ < cpi->Configuration.MaxQ )
      cpi->Configuration.ActiveMaxQ = cpi->Configuration.MaxQ;
  }

  /* Calculate the Q Modifier step size required to cause a step down
     from full target bandwidth to 40% of target between max Q and
     best Q */
  QModStep = 0.5 / (double)((Q_TABLE_SIZE - 1) -
                            cpi->Configuration.ActiveMaxQ);

  /* Set up the cpi->QTargetModifier[] table. */
  for ( i = 0; i < cpi->Configuration.ActiveMaxQ; i++ ) {
    cpi->QTargetModifier[i] = QModifier;
  }
  for ( i = cpi->Configuration.ActiveMaxQ; i < Q_TABLE_SIZE; i++ ) {
    cpi->QTargetModifier[i] = QModifier;
    QModifier -= QModStep;
  }

  /* if we are allowed to drop frames and are falling behind (eg more
     than x frames worth of bandwidth) */
  if ( cpi->pb.info.dropframes_p &&
       ( cpi->DropCount < cpi->MaxConsDroppedFrames) &&
       ( cpi->CarryOver <
         -((ogg_int32_t)cpi->Configuration.TargetBandwidth)) &&
       ( cpi->DropFrameCandidate) ) {
    /* (we didn't do this frame so we should have some left over for
       the next frame) */
    cpi->CarryOver += cpi->frame_target_rate;
    DropFrame = 1;
    cpi->DropCount ++;

    /* Adjust DropFrameTriggerBytes to account for the saving achieved. */
    cpi->DropFrameTriggerBytes =
      (cpi->DropFrameTriggerBytes *
       (DF_CANDIDATE_WINDOW-1))/DF_CANDIDATE_WINDOW;

    /* Even if we drop a frame we should account for it when
        considering key frame seperation. */
    cpi->LastKeyFrame++;
  } else if ( cpi->CarryOver <
              -((ogg_int32_t)cpi->Configuration.TargetBandwidth * 2) ) {
    /* Reduce frame bit target by 1.75% for each 1/10th of a seconds
       worth of -ve carry over down to a minimum of 65% of its
       un-modified value. */

    cpi->ThisFrameTargetBytes =
      (ogg_uint32_t)(cpi->ThisFrameTargetBytes * 0.65);
  } else if ( cpi->CarryOver < 0 ) {
    /* Note that cpi->CarryOver is a -ve here hence 1.0 "+" ... */
    cpi->ThisFrameTargetBytes =
      (ogg_uint32_t)(cpi->ThisFrameTargetBytes *
                     (1.0 + ( ((cpi->CarryOver * 10)/
                               ((ogg_int32_t)cpi->
                                Configuration.TargetBandwidth)) * 0.0175) ));
  }

  if ( !DropFrame ) {
    /*  pick all the macroblock modes and motion vectors */
    ogg_uint32_t InterError;
    ogg_uint32_t IntraError;


    /* Set Baseline filter level. */
    ConfigurePP( &cpi->pp, cpi->pb.info.noise_sensitivity);

    /* Score / analyses the fragments. */
    cpi->MotionScore = YUVAnalyseFrame(&cpi->pp, &KFIndicator );

    /* Get the baseline Q value */
    RegulateQ( cpi, cpi->MotionScore );

    /* Recode blocks if the error score in last frame was high. */
    ResidueBlocksAdded  = 0;
    for ( i = 0; i < cpi->pb.UnitFragments; i++ ){
      if ( !cpi->pb.display_fragments[i] ){
        if ( cpi->LastCodedErrorScore[i] >=
             ResidueErrorThresh[cpi->pb.FrameQIndex] ) {
          cpi->pb.display_fragments[i] = 1; /* Force block update */
          cpi->extra_fragments[i] = 1;      /* Insures up to date
                                               pixel data is used. */
          ResidueBlocksAdded ++;
        }
      }
    }

    /* Adjust the motion score to allow for residue blocks
       added. These are assumed to have below average impact on
       bitrate (Hence ResidueBlockFactor). */
    cpi->MotionScore = cpi->MotionScore +
      (ResidueBlocksAdded / ResidueBlockFactor[cpi->pb.FrameQIndex]);

    /* Estimate the min number of blocks at best Q */
    min_blocks_per_frame =
      (ogg_int32_t)(cpi->ThisFrameTargetBytes /
                    GetEstimatedBpb( cpi, VERY_BEST_Q ));
    if ( min_blocks_per_frame == 0 )
      min_blocks_per_frame = 1;

    /* If we have less than this number then consider adding in some
       extra blocks */
    if ( cpi->MotionScore < min_blocks_per_frame ) {
      min_blocks_per_frame =
        cpi->MotionScore +
        (ogg_int32_t)(((min_blocks_per_frame - cpi->MotionScore) * 4) / 3 );
      UpRegulateDataStream( cpi, VERY_BEST_Q, min_blocks_per_frame );
    }else{
      /* Reset control variable for best quality final pass. */
      cpi->FinalPassLastPos = 0;
    }

    /* Get the modified Q prediction taking into account extra blocks added. */
    RegulateQ( cpi, cpi->MotionScore );

    /* Unless we are already well ahead (4 seconds of data) of the
       projected bitrate */
    if ( cpi->CarryOver <
         (ogg_int32_t)(cpi->Configuration.TargetBandwidth * 4) ){
      /* Look at the predicted Q (pbi->FrameQIndex).  Adjust the
         target bits for this frame based upon projected Q and
         re-calculate.  The idea is that if the Q is better than a
         given (good enough) level then we will try and save some bits
         for use in more difficult segments. */
      cpi->ThisFrameTargetBytes =
        (ogg_int32_t) (cpi->ThisFrameTargetBytes *
                       cpi->QTargetModifier[cpi->pb.FrameQIndex]);

      /* Recalculate Q again */
      RegulateQ( cpi, cpi->MotionScore );
    }


    /* Select modes and motion vectors for each of the blocks : return
       an error score for inter and intra */
    PickModes( cpi, cpi->pb.YSBRows, cpi->pb.YSBCols,
               cpi->pb.info.width,
               &InterError, &IntraError );

    /* decide whether we really should have made this frame a key frame */
    /* forcing out a keyframe if the max interval is up is done at a higher level */
    if( cpi->pb.info.keyframe_auto_p){
      if( ( 2* IntraError < 5 * InterError )
          && ( KFIndicator >= (ogg_uint32_t)
               cpi->pb.info.keyframe_auto_threshold)
          && ( cpi->LastKeyFrame > cpi->pb.info.keyframe_mindistance)
          ){
        CompressKeyFrame(cpi);  /* Code a key frame */
        return;
      }

    }

    /* Increment the frames since last key frame count */
    cpi->LastKeyFrame++;

    /* Proceed with the frame update. */
    UpdateFrame(cpi);
    cpi->DropCount = 0;

    if ( cpi->MotionScore > 0 ){
      /* Note the Quantizer used for each block coded. */
      for ( i = 0; i < cpi->pb.UnitFragments; i++ ){
        if ( cpi->pb.display_fragments[i] ){
          cpi->FragmentLastQ[i] = cpi->pb.ThisFrameQualityValue;
        }
      }

    }
  }else{
    /* even if we 'drop' a frame, a placeholder must be written as we
       currently assume fixed frame rate timebase as Ogg mapping
       invariant */
    UpdateFrame(cpi);
  }
}

/********************** The toplevel: encode ***********************/

static int _ilog(unsigned int v){
  int ret=0;
  while(v){
    ret++;
    v>>=1;
  }
  return(ret);
}

int theora_encode_init(theora_state *th, theora_info *c){
  int i;

  CP_INSTANCE *cpi;

  memset(th, 0, sizeof(*th));
  /*Currently only the 4:2:0 format is supported.*/
  if(c->pixelformat!=OC_PF_420)return OC_IMPL;
  th->internal_encode=cpi=_ogg_calloc(1,sizeof(*cpi));

  dsp_static_init (&cpi->dsp);
  memcpy (&cpi->pb.dsp, &cpi->dsp, sizeof(DspFunctions));

  c->version_major=VERSION_MAJOR;
  c->version_minor=VERSION_MINOR;
  c->version_subminor=VERSION_SUB;

  InitTmpBuffers(&cpi->pb);
  InitPPInstance(&cpi->pp, &cpi->dsp);

  /* Initialise Configuration structure to legal values */
  if(c->quality>63)c->quality=63;
  if(c->quality<0)c->quality=32;
  if(c->target_bitrate<0)c->target_bitrate=0;
  /* we clamp target_bitrate to 24 bits after setting up the encoder */

  cpi->Configuration.BaseQ = c->quality;
  cpi->Configuration.FirstFrameQ = c->quality;
  cpi->Configuration.MaxQ = c->quality;
  cpi->Configuration.ActiveMaxQ = c->quality;

  cpi->MVChangeFactor    =    14;
  cpi->FourMvChangeFactor =   8;
  cpi->MinImprovementForNewMV = 25;
  cpi->ExhaustiveSearchThresh = 2500;
  cpi->MinImprovementForFourMV = 100;
  cpi->FourMVThreshold = 10000;
  cpi->BitRateCapFactor = 1.50;
  cpi->InterTripOutThresh = 5000;
  cpi->MVEnabled = 1;
  cpi->InterCodeCount = 127;
  cpi->BpbCorrectionFactor = 1.0;
  cpi->GoldenFrameEnabled = 1;
  cpi->InterPrediction = 1;
  cpi->MotionCompensation = 1;