C++ BeatsPointer::findPrevBeat方法代码示例

bool BpmControl::syncPhase(EngineBuffer* pOtherEngineBuffer) {
    if (!pOtherEngineBuffer) {
        return false;
    }
    TrackPointer otherTrack = pOtherEngineBuffer->getLoadedTrack();
    BeatsPointer otherBeats = otherTrack ? otherTrack->getBeats() : BeatsPointer();

    // If either track does not have beats, then we can't adjust the phase.
    if (!m_pBeats || !otherBeats) {
        return false;
    }

    // Get the file BPM of each song.
    //double dThisBpm = m_pBeats->getBpm();
    //double dOtherBpm = ControlObject::getControl(
    //ConfigKey(pOtherEngineBuffer->getGroup(), "file_bpm"))->get();

    // Get the current position of both decks
    double dThisPosition = getCurrentSample();
    double dOtherLength = ControlObject::getControl(
        ConfigKey(pOtherEngineBuffer->getGroup(), "track_samples"))->get();
    double dOtherEnginePlayPos = ControlObject::getControl(
        ConfigKey(pOtherEngineBuffer->getGroup(), "visual_playposition"))->get();
    double dOtherPosition = dOtherLength * dOtherEnginePlayPos;

    double dThisPrevBeat = m_pBeats->findPrevBeat(dThisPosition);
    double dThisNextBeat = m_pBeats->findNextBeat(dThisPosition);

    if (dThisPrevBeat == -1 || dThisNextBeat == -1 ||
            dOtherEnginePlayPos == -1 || dOtherLength == 0) {
        return false;
    }

    // Protect against the case where we are sitting exactly on the beat.
    if (dThisPrevBeat == dThisNextBeat) {
        dThisNextBeat = m_pBeats->findNthBeat(dThisPosition, 2);
    }

    double dOtherPrevBeat = otherBeats->findPrevBeat(dOtherPosition);
    double dOtherNextBeat = otherBeats->findNextBeat(dOtherPosition);

    if (dOtherPrevBeat == -1 || dOtherNextBeat == -1) {
        return false;
    }

    // Protect against the case where we are sitting exactly on the beat.
    if (dOtherPrevBeat == dOtherNextBeat) {
        dOtherNextBeat = otherBeats->findNthBeat(dOtherPosition, 2);
    }

    double dThisBeatLength = fabs(dThisNextBeat - dThisPrevBeat);
    double dOtherBeatLength = fabs(dOtherNextBeat - dOtherPrevBeat);
    double dOtherBeatFraction = (dOtherPosition - dOtherPrevBeat) / dOtherBeatLength;

    double dNewPlaypos;
    bool this_near_next = dThisNextBeat - dThisPosition <= dThisPosition - dThisPrevBeat;
    bool other_near_next = dOtherNextBeat - dOtherPosition <= dOtherPosition - dOtherPrevBeat;

    // We want our beat fraction to be identical to theirs.

    // If the two tracks have similar alignment, adjust phase is straight-
    // forward.  Use the same fraction for both beats, starting from the previous
    // beat.  But if This track is nearer to the next beat and the Other track
    // is nearer to the previous beat, use This Next beat as the starting point
    // for the phase. (ie, we pushed the sync button late).  If This track
    // is nearer to the previous beat, but the Other track is nearer to the
    // next beat, we pushed the sync button early so use the double-previous
    // beat as the basis for the adjustment.
    //
    // This makes way more sense when you're actually mixing.
    //
    // TODO(XXX) Revisit this logic once we move away from tempo-locked,
    // infinite beatgrids because the assumption that findNthBeat(-2) always
    // works will be wrong then.

    if (this_near_next == other_near_next) {
        dNewPlaypos = dThisPrevBeat + dOtherBeatFraction * dThisBeatLength;
    } else if (this_near_next && !other_near_next) {
        dNewPlaypos = dThisNextBeat + dOtherBeatFraction * dThisBeatLength;
    } else {  //!this_near_next && other_near_next
        dThisPrevBeat = m_pBeats->findNthBeat(dThisPosition, -2);
        dNewPlaypos = dThisPrevBeat + dOtherBeatFraction * dThisBeatLength;
    }

    // We might be seeking outside the loop.
    const bool loop_enabled = m_pLoopEnabled->get() > 0.0;
    const double loop_start_position = m_pLoopStartPosition->get();
    const double loop_end_position = m_pLoopEndPosition->get();

    // Cases for sanity:
    //
    // CASE 1
    // Two identical 1-beat loops, out of phase by X samples.
    // Other deck is at its loop start.
    // This deck is half way through. We want to jump forward X samples to the loop end point.
    //
    // Two identical 1-beat loop, out of phase by X samples.
    // Other deck is

    // If sync target is 50% through the beat,
//.........这里部分代码省略.........