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IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE), STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include "CASMPTETimeBase.h" #include "CAException.h" /* enum { kSMPTETimeType24 = 0, kSMPTETimeType25 = 1, kSMPTETimeType30Drop = 2, kSMPTETimeType30 = 3, kSMPTETimeType2997 = 4, kSMPTETimeType2997Drop = 5, kSMPTETimeType60 = 6, kSMPTETimeType5994 = 7 }; */ static const SInt8 gMTCTypes[] = { 0, 1, 2, 3, 3, 2, -1, -1 }; // map our constants to MIDI Time Code representations static const double gFramesPerSecond[] = { 24., 25., 29.97, 30., 29.97, 29.97 * .999 /* ????? */, 60., 59.94 }; static const UInt8 gFormatFramesPerSecond[] = { 24, 25, 30, 30, 30, 30, 60, 60 }; bool CASMPTETimeBase::SetFormat(UInt32 inSMPTEFormat) { if (inSMPTEFormat > kSMPTETimeType5994) return false; mMTCType = gMTCTypes[inSMPTEFormat]; mIsDropFrame = (mMTCType == 2); mFramesPerSecond = gFramesPerSecond[inSMPTEFormat]; mFormatFramesPerSecond = gFormatFramesPerSecond[inSMPTEFormat]; mFormat = inSMPTEFormat; return true; } /* http://www.phatnav.com/wiki/wiki.phtml?title=SMPTE_time_code To correct this, drop frame SMPTE timecode drops frame numbers 0 and 1 of the first second of every minute, and includes them when the number of minutes is divisible by ten. This almost perfectly compensates for the difference in rate, leaving a residual timing error of roughly 86.4 microseconds per day, an error of only 0.001 ppm. Note: only timecode frame numbers are dropped. Video frames continue in sequence. NOTE: drop frame calculations all assume 30 fps = 1800 frames/minute = 18000 frames/10 minutes */ void CASMPTETimeBase::SecondsToSMPTETime(Float64 inSeconds, UInt16 inSubframeDivisor, SMPTETime & outSMPTETime) const { // time in subframes int bitsPerSecond = inSubframeDivisor * mFormatFramesPerSecond; int absBits = int(inSeconds * bitsPerSecond + 0.5); // round int bitsInDay = bitsPerSecond * 60 * 60 * 24; while (absBits < 0) absBits += bitsInDay; while (absBits >= bitsInDay) absBits -= bitsInDay; // if it's drop frame, add back a number of frames to fix up representation if (mIsDropFrame) { // drop frame int bitsPer10Minutes = inSubframeDivisor * 17982; // 18000 - 18 dropped // how many 10-minute periods? count 18 dropped frames for each int minutes10 = (absBits / bitsPer10Minutes); int extraFrames = 18 * minutes10; int frames10 = (absBits / inSubframeDivisor) % 17982; // position in 10-minute cycle if (frames10 >= 1800) { // at or past the first minute // minute 0 has 1800 frames, subsequent minutes have 1798 frames // so add 2 frames per minute extraFrames += 2 + 2 * ((frames10 - 1800) / 1798); } absBits = int(inSeconds * bitsPerSecond + 0.5) + extraFrames * inSubframeDivisor; } int div; div = (bitsPerSecond * 60 * 60); outSMPTETime.mHours = absBits / div; absBits %= div; div = (bitsPerSecond * 60); outSMPTETime.mMinutes = absBits / div; absBits %= div; outSMPTETime.mSeconds = absBits / bitsPerSecond; absBits %= bitsPerSecond; outSMPTETime.mFrames = absBits / inSubframeDivisor; outSMPTETime.mSubframes = absBits %= inSubframeDivisor; outSMPTETime.mSubframeDivisor = inSubframeDivisor; outSMPTETime.mType = (SMPTETimeType) mFormat; } bool CASMPTETimeBase::SMPTETimeToSeconds(const SMPTETime & inSMPTETime, Float64 & outSeconds) const { if (inSMPTETime.mHours > 23 || inSMPTETime.mMinutes > 59 || inSMPTETime.mSeconds > 59 || inSMPTETime.mFrames >= mFormatFramesPerSecond || inSMPTETime.mSubframes >= inSMPTETime.mSubframeDivisor) return false; // first, compute it assuming no dropped frames int frames = (inSMPTETime.mFrames + mFormatFramesPerSecond * // frames (inSMPTETime.mSeconds + 60 * // seconds (inSMPTETime.mMinutes + 60 * // minutes inSMPTETime.mHours))); // hours // now, figure out the number of dropped frames if (mIsDropFrame) { frames -= inSMPTETime.mHours * 6 * 18; // hours, 18 frames for each 10 minutes int minutes = inSMPTETime.mMinutes; frames -= (minutes / 10) * 18; // 18 frames per 10-minute period minutes %= 10; if (minutes) { if (inSMPTETime.mFrames < 2) return false; // illegal -- dropped frame frames -= minutes * 2; } } int bits = inSMPTETime.mSubframes + inSMPTETime.mSubframeDivisor * frames; outSeconds = double(bits) / double(mFormatFramesPerSecond * inSMPTETime.mSubframeDivisor); return true; } // increment a 32-bit MTC SMPTE frame representation // HHMMSSFF (nibbles) SMPTE_HMSF CASMPTETimeBase::AdvanceFrame(SMPTE_HMSF hmsf, int nToAdvance) const { while (--nToAdvance >= 0) { hmsf += 1; if ((hmsf & 0xFF) == UInt32(mFormatFramesPerSecond)) { // next second hmsf &= ~0xFF; hmsf += 0x100; if ((hmsf & 0xFF00) == (60 << 8)) { // 60 seconds hmsf &= ~0xFF00; hmsf += 0x10000; if ((hmsf & 0xFF0000) == (60 << 16)) { // 60 minutes hmsf &= ~0xFF0000; hmsf += 0x1000000; if ((hmsf & 0x1F000000) == (24 << 24)) // 24 hours hmsf &= ~0x1F000000; } } } if (mIsDropFrame && (hmsf & 0xFFFE) == 0 && // either of first two frames of first second ((hmsf & 0x00FF0000) >> 16) % 10 != 0) // not the first of a 10-minute period hmsf += 2; // drop the two frames } return hmsf; } // convert SMPTE representation as four bytes in a UInt32 to number of frames since 0 UInt32 CASMPTETimeBase::HMSFToAbsoluteFrame(SMPTE_HMSF hmsf) const { // first, compute it assuming no dropped frames UInt32 frames = (hmsf & 0xFF) + mFormatFramesPerSecond * ( // frames ((hmsf >> 8) & 0xFF) + 60 * ( // seconds ((hmsf >> 16) & 0xFF) + 60 * ( // minutes (hmsf >> 24) & 0x1F))); // hours // now, figure out the number of dropped frames if (mIsDropFrame) { frames -= ((hmsf & 0x1F000000) >> 24) * 6 * 18; // hours UInt16 minutes = (hmsf & 0x00FF0000) >> 16; frames -= (minutes / 10) * 18; // 10-minute periods minutes %= 10; if (minutes) frames -= minutes * 2; } return frames; }