134 lines
5.3 KiB
C++
134 lines
5.3 KiB
C++
/* _______ ____ __ ___ ___
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* \ _ \ \ / \ / \ \ / / ' ' '
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* | | \ \ | | || | \/ | . .
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* | | | | | | || ||\ /| |
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* | | | | | | || || \/ | | ' ' '
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* | | | | | | || || | | . .
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* | |_/ / \ \__// || | |
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* /_______/ynamic \____/niversal /__\ /____\usic /| . . ibliotheque
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* / \
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* / . \
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* resamp2.inc - Resampling helper template. / / \ \
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* | < / \_
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* By Bob and entheh. | \/ /\ /
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* \_ / > /
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* In order to find a good trade-off between | \ / /
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* speed and accuracy in this code, some tests | ' /
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* were carried out regarding the behaviour of \__/
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* long long ints with gcc. The following code
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* was tested:
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*
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* int a, b, c;
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* c = ((long long)a * b) >> 16;
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*
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* DJGPP GCC Version 3.0.3 generated the following assembly language code for
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* the multiplication and scaling, leaving the 32-bit result in EAX.
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*
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* movl -8(%ebp), %eax ; read one int into EAX
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* imull -4(%ebp) ; multiply by the other; result goes in EDX:EAX
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* shrdl $16, %edx, %eax ; shift EAX right 16, shifting bits in from EDX
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*
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* Note that a 32*32->64 multiplication is performed, allowing for high
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* accuracy. On the Pentium 2 and above, shrdl takes two cycles (generally),
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* so it is a minor concern when four multiplications are being performed
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* (the cubic resampler). On the Pentium MMX and earlier, it takes four or
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* more cycles, so this method is unsuitable for use in the low-quality
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* resamplers.
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*
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* Since "long long" is a gcc-specific extension, we use LONG_LONG instead,
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* defined in dumb.h. We may investigate later what code MSVC generates, but
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* if it seems too slow then we suggest you use a good compiler.
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*
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* FIXME: these comments are somewhat out of date now.
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*/
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#define SUFFIX3 _1
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/* For convenience, returns nonzero on stop. */
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static int process_pickup(DUMB_RESAMPLER *resampler)
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{
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if (resampler->overshot < 0) {
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resampler->overshot = 0;
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dumb_resample(resampler, NULL, 2, MONO_DEST_VOLUME_ZEROS, 1.0f); /* Doesn't matter which SUFFIX3. */
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COPYSRC(resampler->X, 0, resampler->X, 1);
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}
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for (;;) {
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SRCTYPE *src = resampler->src;
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if (resampler->dir < 0) {
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if (resampler->overshot >= 3 && resampler->pos+3 >= resampler->start) COPYSRC(resampler->X, 0, src, resampler->pos+3);
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if (resampler->overshot >= 2 && resampler->pos+2 >= resampler->start) COPYSRC(resampler->X, 1, src, resampler->pos+2);
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if (resampler->overshot >= 1 && resampler->pos+1 >= resampler->start) COPYSRC(resampler->X, 2, src, resampler->pos+1);
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resampler->overshot = resampler->start - resampler->pos - 1;
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} else {
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if (resampler->overshot >= 3 && resampler->pos-3 < resampler->end) COPYSRC(resampler->X, 0, src, resampler->pos-3);
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if (resampler->overshot >= 2 && resampler->pos-2 < resampler->end) COPYSRC(resampler->X, 1, src, resampler->pos-2);
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if (resampler->overshot >= 1 && resampler->pos-1 < resampler->end) COPYSRC(resampler->X, 2, src, resampler->pos-1);
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resampler->overshot = resampler->pos - resampler->end;
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}
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if (resampler->overshot < 0) {
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resampler->overshot = 0;
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return 0;
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}
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if (!resampler->pickup) {
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resampler->dir = 0;
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return 1;
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}
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(*resampler->pickup)(resampler, resampler->pickup_data);
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if (resampler->dir == 0) return 1;
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ASSERT(resampler->dir == -1 || resampler->dir == 1);
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}
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}
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/* Create mono destination resampler. */
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/* SUFFIX3 was set above. */
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#define VOLUME_PARAMETERS MONO_DEST_VOLUME_PARAMETERS
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#define VOLUME_VARIABLES MONO_DEST_VOLUME_VARIABLES
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#define SET_VOLUME_VARIABLES SET_MONO_DEST_VOLUME_VARIABLES
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#define VOLUMES_ARE_ZERO MONO_DEST_VOLUMES_ARE_ZERO
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#define MIX_ALIAS(op, offset) MONO_DEST_MIX_ALIAS(op, offset)
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#define MIX_LINEAR(op, o0, o1) MONO_DEST_MIX_LINEAR(op, o0, o1)
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#define MIX_CUBIC(op, x0, x3, o0, o1, o2, o3) MONO_DEST_MIX_CUBIC(op, x0, x3, o0, o1, o2, o3)
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#define MIX_ZEROS(op) *dst++ op 0
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#include "resamp3.inc"
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/* Create stereo destination resampler. */
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#define SUFFIX3 _2
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#define VOLUME_PARAMETERS float volume_left, float volume_right
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#define VOLUME_VARIABLES lvol, rvol
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#define SET_VOLUME_VARIABLES { \
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lvol = (int)floor(volume_left * 65536.0 + 0.5); \
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rvol = (int)floor(volume_right * 65536.0 + 0.5); \
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}
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#define VOLUMES_ARE_ZERO (lvol == 0 && rvol == 0)
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#define MIX_ALIAS(op, offset) STEREO_DEST_MIX_ALIAS(op, offset)
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#define MIX_LINEAR(op, o0, o1) STEREO_DEST_MIX_LINEAR(op, o0, o1)
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#define MIX_CUBIC(op, x0, x3, o0, o1, o2, o3) STEREO_DEST_MIX_CUBIC(op, x0, x3, o0, o1, o2, o3)
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#define MIX_ZEROS(op) { *dst++ op 0; *dst++ op 0; }
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#include "resamp3.inc"
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#undef STEREO_DEST_MIX_CUBIC
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#undef MONO_DEST_MIX_CUBIC
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#undef STEREO_DEST_MIX_LINEAR
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#undef MONO_DEST_MIX_LINEAR
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#undef STEREO_DEST_MIX_ALIAS
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#undef MONO_DEST_MIX_ALIAS
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#undef MONO_DEST_VOLUMES_ARE_ZERO
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#undef SET_MONO_DEST_VOLUME_VARIABLES
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#undef MONO_DEST_VOLUME_ZEROS
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#undef MONO_DEST_VOLUME_VARIABLES
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#undef MONO_DEST_VOLUME_PARAMETERS
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#undef COPYSRC2
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#undef COPYSRC
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#undef DIVIDE_BY_SRC_CHANNELS
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#undef SRC_CHANNELS
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#undef SUFFIX2
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