39 lines
1 KiB
C++
39 lines
1 KiB
C++
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// Copyright (c) 1996 Microsoft Corporation. All Rights Reserved.
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/**********************************************************************
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Timecode helper routines
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With a bit of care to not overflow or bruise the potentialy large numbers...
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**********************************************************************/
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#include <wtypes.h> // LONGLONG
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#include <stdio.h>
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LONGLONG extrapolate(LONGLONG sample1, LONGLONG time1,
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LONGLONG sample2, LONGLONG time2, LONGLONG sampleN)
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{
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LONGLONG sampleTime;
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/* NOTE: deltas should be fairly small so we don't mind losing the bits */
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double deltaSample = (double)(sample2 - sample1);
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double deltaTime = (double)(time2 - time1);
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double ratio;
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ratio = deltaTime / deltaSample; // floating point ratio
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sampleTime = LONGLONG((double)(sampleN - sample1) * ratio);
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sampleTime+= time1; // add the offset
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return(sampleTime);
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}
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#ifdef TEST
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// XXX flesh out the test code!
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main()
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{
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LONGLONG foo = extrapolate(1, 1, 6, 3, 2);
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printf("%d",(int)foo);
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}
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#endif /* TEST */
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