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simpler delta decreasing algorithm patch by (Jeff Muizelaar <jrmuizel at student dot cs dot uwaterloo dot ca>)
Originally committed as revision 3369 to svn://svn.ffmpeg.org/ffmpeg/trunk
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d8665b1274
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@ -515,7 +515,7 @@ static int encode_exp(uint8_t encoded_exp[N/2],
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int nb_exps,
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int exp_strategy)
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{
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int group_size, nb_groups, i, j, k, recurse, exp_min, delta;
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int group_size, nb_groups, i, j, k, exp_min;
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uint8_t exp1[N/2];
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switch(exp_strategy) {
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@ -550,25 +550,13 @@ static int encode_exp(uint8_t encoded_exp[N/2],
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if (exp1[0] > 15)
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exp1[0] = 15;
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/* Iterate until the delta constraints between each groups are
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satisfyed. I'm sure it is possible to find a better algorithm,
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but I am lazy */
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do {
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recurse = 0;
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for(i=1;i<=nb_groups;i++) {
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delta = exp1[i] - exp1[i-1];
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if (delta > 2) {
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/* if delta too big, we encode a smaller exponent */
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exp1[i] = exp1[i-1] + 2;
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} else if (delta < -2) {
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/* if delta is too small, we must decrease the previous
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exponent, which means we must recurse */
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recurse = 1;
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exp1[i-1] = exp1[i] + 2;
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}
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}
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} while (recurse);
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/* Decrease the delta between each groups to within 2
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* so that they can be differentially encoded */
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for (i=1;i<=nb_groups;i++)
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exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
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for (i=nb_groups-1;i>=0;i--)
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exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
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/* now we have the exponent values the decoder will see */
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encoded_exp[0] = exp1[0];
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k = 1;
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