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TransceiverUHD: Scale converter output appropriately for 8-bits 

Existing integer-float converter didn't accomodate for the final
transceiver output converting to 8-bits. The resulting effect was
integer overflow above a certain signal input level dependent on RF
receive gain. Resolve by scaling to allow full input level range.

Signed-off-by: Tom Tsou <tom@tsou.cc>
This commit is contained in:
Tom Tsou 2015-01-23 19:02:39 -08:00 committed by Michael Iedema
parent 89ec9e6046
commit 6e9711c0ff
3 changed files with 43 additions and 30 deletions
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5
TransceiverUHD/RadioInterface.cpp
View File

@ -58,6 +58,9 @@ extern "C" {
/* Universal resampling parameters */
#define NUMCHUNKS 32
/* Receive scaling factor for 16 to 8 bits */
#define CONVERT_RX_SCALE (128.0 / 32768.0)
UMTS::Time VectorQueue::nextTime() const
{
UMTS::Time retVal;
@ -319,7 +322,7 @@ bool RadioInterface::pullBuffer(void)
short *convert_in = convertRecvBuffer;
float *convert_out = (float *) (outerRecvBuffer->begin() + dnsampler->len());
convert_short_float(convert_out, convert_in, outchunk * 2);
convert_short_float(convert_out, convert_in, CONVERT_RX_SCALE, outchunk * 2);
underrun |= localUnderrun;
readTimestamp += outchunk;

54
TransceiverUHD/convert.c
View File

@ -34,10 +34,12 @@
/* 16*N 16-bit signed integer converted to single precision floats */
static void _sse_convert_si16_ps_16n(float *restrict out,
short *restrict in,
int len)
float scale, int len)
{
__m128i m0, m1, m2, m3, m4, m5;
__m128 m6, m7, m8, m9;
__m128 m6, m7, m8, m9, m10;
m10 = _mm_load1_ps(&scale);
for (int i = 0; i < len / 16; i++) {
/* Load (unaligned) packed floats */
@ -58,6 +60,12 @@ static void _sse_convert_si16_ps_16n(float *restrict out,
m8 = _mm_cvtepi32_ps(m4);
m9 = _mm_cvtepi32_ps(m5);
/* Scale */
m6 = _mm_mul_ps(m6, m10);
m7 = _mm_mul_ps(m7, m10);
m8 = _mm_mul_ps(m8, m10);
m9 = _mm_mul_ps(m9, m10);
/* Store */
_mm_storeu_ps(&out[16 * i + 0], m6);
_mm_storeu_ps(&out[16 * i + 4], m7);
@ -69,30 +77,31 @@ static void _sse_convert_si16_ps_16n(float *restrict out,
/* 16*N 16-bit signed integer conversion with remainder */
static void _sse_convert_si16_ps(float *restrict out,
short *restrict in,
int len)
float scale, int len)
{
int start = len / 16 * 16;
_sse_convert_si16_ps_16n(out, in, len);
_sse_convert_si16_ps_16n(out, in, scale, len);
for (int i = 0; i < len % 16; i++)
out[start + i] = in[start + i];
out[start + i] = in[start + i] * scale;
}
#endif /* HAVE_SSE4_1 */
/* 8*N single precision floats scaled and converted to 16-bit signed integer */
static void _sse_convert_scale_ps_si16_8n(short *restrict out,
static void _sse_convert_ps_si16_8n(short *restrict out,
float *restrict in,
float scale, int len)
{
__m128 m0, m1, m2;
__m128i m4, m5;
m2 = _mm_load1_ps(&scale);
for (int i = 0; i < len / 8; i++) {
/* Load (unaligned) packed floats */
m0 = _mm_loadu_ps(&in[8 * i + 0]);
m1 = _mm_loadu_ps(&in[8 * i + 4]);
m2 = _mm_load1_ps(&scale);
/* Scale */
m0 = _mm_mul_ps(m0, m2);
@ -109,33 +118,34 @@ static void _sse_convert_scale_ps_si16_8n(short *restrict out,
}
/* 8*N single precision floats scaled and converted with remainder */
static void _sse_convert_scale_ps_si16(short *restrict out,
static void _sse_convert_ps_si16(short *restrict out,
float *restrict in,
float scale, int len)
{
int start = len / 8 * 8;
_sse_convert_scale_ps_si16_8n(out, in, scale, len);
_sse_convert_ps_si16_8n(out, in, scale, len);
for (int i = 0; i < len % 8; i++)
out[start + i] = in[start + i] * scale;
}
/* 16*N single precision floats scaled and converted to 16-bit signed integer */
static void _sse_convert_scale_ps_si16_16n(short *restrict out,
static void _sse_convert_ps_si16_16n(short *restrict out,
float *restrict in,
float scale, int len)
{
__m128 m0, m1, m2, m3, m4;
__m128i m5, m6, m7, m8;
m4 = _mm_load1_ps(&scale);
for (int i = 0; i < len / 16; i++) {
/* Load (unaligned) packed floats */
m0 = _mm_loadu_ps(&in[16 * i + 0]);
m1 = _mm_loadu_ps(&in[16 * i + 4]);
m2 = _mm_loadu_ps(&in[16 * i + 8]);
m3 = _mm_loadu_ps(&in[16 * i + 12]);
m4 = _mm_load1_ps(&scale);
/* Scale */
m0 = _mm_mul_ps(m0, m4);
@ -157,7 +167,7 @@ static void _sse_convert_scale_ps_si16_16n(short *restrict out,
}
}
#else /* HAVE_SSE3 */
static void convert_scale_ps_si16(short *out, float *in, float scale, int len)
static void convert_ps_si16(short *out, float *in, float scale, int len)
{
for (int i = 0; i < len; i++)
out[i] = in[i] * scale;
@ -165,10 +175,10 @@ static void convert_scale_ps_si16(short *out, float *in, float scale, int len)
#endif
#ifndef HAVE_SSE4_1
static void convert_si16_ps(float *out, short *in, int len)
static void convert_si16_ps(float *out, short *in, float scale, int len)
{
for (int i = 0; i < len; i++)
out[i] = in[i];
out[i] = in[i] * scale;
}
#endif
@ -176,24 +186,24 @@ void convert_float_short(short *out, float *in, float scale, int len)
{
#ifdef HAVE_SSE3
if (!(len % 16))
_sse_convert_scale_ps_si16_16n(out, in, scale, len);
_sse_convert_ps_si16_16n(out, in, scale, len);
else if (!(len % 8))
_sse_convert_scale_ps_si16_8n(out, in, scale, len);
_sse_convert_ps_si16_8n(out, in, scale, len);
else
_sse_convert_scale_ps_si16(out, in, scale, len);
_sse_convert_ps_si16(out, in, scale, len);
#else
convert_scale_ps_si16(out, in, scale, len);
convert_ps_si16(out, in, scale, len);
#endif
}
void convert_short_float(float *out, short *in, int len)
void convert_short_float(float *out, short *in, float scale, int len)
{
#ifdef HAVE_SSE4_1
if (!(len % 16))
_sse_convert_si16_ps_16n(out, in, len);
_sse_convert_si16_ps_16n(out, in, scale, len);
else
_sse_convert_si16_ps(out, in, len);
_sse_convert_si16_ps(out, in, scale, len);
#else
convert_si16_ps(out, in, len);
convert_si16_ps(out, in, scale, len);
#endif
}

2
TransceiverUHD/convert.h
View File

@ -2,6 +2,6 @@
#define _CONVERT_H_
void convert_float_short(short *out, float *in, float scale, int len);
void convert_short_float(float *out, short *in, int len);
void convert_short_float(float *out, short *in, float scale, int len);
#endif /* _CONVERT_H_ */