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audioconvert: somewhat avoid precision loss in S32 to F32 conversion

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At the very least, we should go through s25_32 intermediate
instead of s24_32, to avoid needlessly loosing 1 LSB precision bit.

That being said, i suspect it's still not doing the right thing.
Why are we silently dropping those 7 LSB bits?
Is that really the way to do it?
This commit is contained in:
Roman Lebedev 2024-06-14 02:00:27 +03:00
parent 175d533b56
commit c517865864
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GPG key ID: 083C3EBB4A1689E0
4 changed files with 38 additions and 46 deletions
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6
spa/plugins/audioconvert/fmt-ops-sse2.c
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@ -335,7 +335,7 @@ conv_s32_to_f32d_1s_sse2(void *data, void * SPA_RESTRICT dst[], const void * SPA
float *d0 = dst[0];
uint32_t n, unrolled;
__m128i in;
__m128 out, factor = _mm_set1_ps(1.0f / S24_SCALE);
__m128 out, factor = _mm_set1_ps(1.0f / S25_SCALE);
if (SPA_IS_ALIGNED(d0, 16))
unrolled = n_samples & ~3;
@ -347,14 +347,14 @@ conv_s32_to_f32d_1s_sse2(void *data, void * SPA_RESTRICT dst[], const void * SPA
s[1*n_channels],
s[2*n_channels],
s[3*n_channels]);
in = _mm_srai_epi32(in, 8);
in = _mm_srai_epi32(in, 7);
out = _mm_cvtepi32_ps(in);
out = _mm_mul_ps(out, factor);
_mm_store_ps(&d0[n], out);
s += 4*n_channels;
}
for(; n < n_samples; n++) {
out = _mm_cvtsi32_ss(factor, s[0]>>8);
out = _mm_cvtsi32_ss(factor, s[0]>>7);
out = _mm_mul_ss(out, factor);
_mm_store_ss(&d0[n], out);
s += n_channels;