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Fix off by one error in fix_28_t

This commit is contained in:
George Norton 2023-08-26 16:59:37 +01:00
parent 1e6896f918
commit b120a7c397
2 changed files with 6 additions and 5 deletions
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9
firmware/code/fix16.inl
View File

@ -32,11 +32,12 @@ static inline fix3_28_t norm_fix3_28_from_s16sample(int16_t a) {
/* So, we're using a Q3.28 fixed point system here, and we want the incoming
audio signal to be represented as a number between -1 and 1. To do this,
we need the 16-bit value to map to the 28-bit right-of-decimal field in
our fixed point number. 28-16 = 12, so we shift the incoming value by
our fixed point number. The 16 bit samples are siged, so bit 15 needs to
be positioned at bit 28. 28-15 = 13, so we shift the incoming value by
that much to covert it to the desired Q3.28 format and do the normalization
all in one go.
*/
return (fix3_28_t)a << 12;
return (fix3_28_t)a << 13;
}
/// @brief Convert fixed point samples into signed integer. Used to convert
@ -69,9 +70,9 @@ static inline int16_t norm_fix3_28_to_s16sample(fix3_28_t a) {
}
}
/* When we converted the USB audio sample to a fixed point number, we applied
a normalization, or a gain of 1/65536. To convert it back, we can undo that
a normalization, or a gain of 1/32767. To convert it back, we can undo that
by shifting it back by the same amount we shifted it in the first place. */
return (a >> 12);
return (a >> 13);
}
static inline fix3_28_t fix3_28_from_flt(float a) {

2
firmware/code/run.c
View File

@ -194,7 +194,7 @@ void __no_inline_not_in_flash_func(core1_entry)() {
x_f16 = bqf_transform(x_f16, &bqf_filters_right[j],
&bqf_filters_mem_right[j]);
out[i] = (int16_t) norm_fix3_28_to_s16sample(x_f16);
out[i] = (int32_t) norm_fix3_28_to_s16sample(x_f16);
}
}