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swresample/rematrix: Use error diffusion to avoid error in the DC component of the matrix 

This fixes the sum of the integer coefficients ending up summing to a value
larger than the value representing unity.

This issue occurs with qN0.dts when converting to stereo

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2016-05-15 18:33:09 +02:00
parent 35c23bf67d
commit 7fe81bc4f8
1 changed files with 9 additions and 3 deletions
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12
libswresample/rematrix.c
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@ -371,9 +371,15 @@ av_cold int swri_rematrix_init(SwrContext *s){
s->native_one = av_mallocz(sizeof(int));
if (!s->native_matrix || !s->native_one)
return AVERROR(ENOMEM);
for (i = 0; i < nb_out; i++)
for (j = 0; j < nb_in; j++)
((int*)s->native_matrix)[i * nb_in + j] = lrintf(s->matrix[i][j] * 32768);
for (i = 0; i < nb_out; i++) {
double rem = 0;
for (j = 0; j < nb_in; j++) {
double target = s->matrix[i][j] * 32768 + rem;
((int*)s->native_matrix)[i * nb_in + j] = lrintf(target);
rem += target - ((int*)s->native_matrix)[i * nb_in + j];
}
}
*((int*)s->native_one) = 32768;
s->mix_1_1_f = (mix_1_1_func_type*)copy_s16;
s->mix_2_1_f = (mix_2_1_func_type*)sum2_s16;