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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 /* 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, 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 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 that much to covert it to the desired Q3.28 format and do the normalization
all in one go. 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 /// @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 /* 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. */ 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) { 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], x_f16 = bqf_transform(x_f16, &bqf_filters_right[j],
&bqf_filters_mem_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);
} }
} }