shithub: ft2-clone

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Added some comments

Added some comments about interpolation tap look-up, to prevent people from thinking that the mixer is buggy.

--- a/src/ft2_mix_macros.h

+++ b/src/ft2_mix_macros.h

@@ -117,6 +117,16 @@

 	s0 = ((s0 * t[0]) + (s1 * t[1]) + (s2 * t[2]) + (s3 * t[3])) >> CUBIC_QUANTSHIFT; \

 } \

+/* 8bitbubsy: It may look like we are potentially going out of bounds by looking up sample point

+** -1, 1 and 2, but the sample data is actually padded on both the left (negative) and right side,

+** where correct samples are stored according to loop mode (or no loop).

+**

+** The only issue is that the -1 look-up gets wrong information if loopStart>0 on looped-samples,

+** and the sample-position is at loopStart. The spline will get ever so slighty wrong because of this,

+** but it's barely audible anyway. Doing it elsewise would require a refactoring of how the audio mixer

+** works!

+*/

+

 #define RENDER_8BIT_SMP_INTRP \

 	assert(smpPtr >= CDA_LinearAdr && smpPtr < CDA_LinearAdr+v->SLen); \

 	sample = smpPtr[-1]; \

@@ -179,6 +189,11 @@

 	s2 = (s2 - s1) >> 1; \

 	s2 = (s2 * (int32_t)f) >> (16 - 1); \

 	s1 += s2; \

+

+/* 8bitbubsy: It may look like we are potentially going out of bounds by looking up sample point

+** 1, but the sample data is actually padded on the right side, where a correct sample is stored

+** according to loop mode (or no loop). This is how original FT2 (MS-DOS) does it as well.

+*/

 #define RENDER_8BIT_SMP_INTRP \

 	assert(smpPtr >= CDA_LinearAdr && smpPtr < CDA_LinearAdr+v->SLen); \