/*

     File: AVTimecodeUtilities.m

 Abstract:  Timecode utilities to convert frame number to timecode and vice versa. 

  Version: 1.2

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 */

#import "AVTimecodeUtilities.h"

enum {

    tcNegativeFlag = 0x80  /* negative bit is in minutes */

};

int64_t frameNumberForTimecodeUsingFrameQuanta(CVSMPTETime timecode, uint32_t frameQuanta, uint32_t tcFlag)

{

    int64_t frameNumber = 0;

    frameNumber = timecode.frames;

    frameNumber += timecode.seconds * frameQuanta;

    frameNumber += (timecode.minutes & ~tcNegativeFlag) * frameQuanta * 60;

    frameNumber += timecode.hours * frameQuanta * 60 * 60;

    int64_t fpm = frameQuanta * 60;

    if (tcFlag & kCMTimeCodeFlag_DropFrame) {

        int64_t fpm10 = fpm * 10;

        int64_t num10s = frameNumber / fpm10;

        int64_t frameAdjust = -num10s*(9*2);

        int64_t numFramesLeft = frameNumber % fpm10;

        if (numFramesLeft > 1) {

            int64_t num1s = numFramesLeft / fpm;

            if (num1s > 0) {

                frameAdjust -= (num1s-1)*2;

                numFramesLeft = numFramesLeft % fpm;

                if (numFramesLeft > 1)

                    frameAdjust -= 2;

                else

                    frameAdjust -= (numFramesLeft+1);

            }

        }

        frameNumber += frameAdjust;

    }

    if (timecode.minutes & tcNegativeFlag) //check for kCMTimeCodeFlag_NegTimesOK here

        frameNumber = -frameNumber;

    return frameNumber;

}

CVSMPTETime timecodeForFrameNumberUsingFrameQuanta(int64_t frameNumber, uint32_t frameQuanta, uint32_t tcFlag)

{

    CVSMPTETime timecode = {0};

    short fps = frameQuanta;

    BOOL neg = FALSE;

    if (frameNumber < 0) {

        neg = TRUE;

        frameNumber = -frameNumber;

    }

    if (tcFlag & kCMTimeCodeFlag_DropFrame) {

        int64_t fpm = fps*60 - 2;

        int64_t fpm10 = fps*10*60 - 9*2;

        int64_t num10s = frameNumber / fpm10;

        int64_t frameAdjust = num10s*(9*2);

        int64_t numFramesLeft = frameNumber % fpm10;

        if (numFramesLeft >= fps*60) {

            numFramesLeft -= fps*60;

            int64_t num1s = numFramesLeft / fpm;

            frameAdjust += (num1s+1)*2;

        }

        frameNumber += frameAdjust;

    }

    timecode.frames = frameNumber % fps;

    frameNumber /= fps;

    timecode.seconds = frameNumber % 60;

    frameNumber /= 60;

    timecode.minutes = frameNumber % 60;

    frameNumber /= 60;

    if (tcFlag & kCMTimeCodeFlag_24HourMax) {

        frameNumber %= 24;

        if (neg && !(tcFlag & kCMTimeCodeFlag_NegTimesOK)) {

            neg = FALSE;

            frameNumber = 23 - frameNumber;

        }

    }

    timecode.hours = frameNumber;

    if (neg) {

        timecode.minutes |= tcNegativeFlag;

    }

    timecode.flags = kCVSMPTETimeValid;

    return timecode;

}