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Downsample filtering.

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This commit is contained in:
John Greb
2014-11-17 19:51:36 +00:00
parent ff312a52a3
commit dcc9f1917c
3 changed files with 56 additions and 35 deletions
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plugins/samplesource/rtlsdr/rtlsdrthread.cpp
+18 -16
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@@ -96,7 +96,7 @@ void RTLSDRThread::decimate4(SampleVector::iterator* it, const quint8* buf, qint
for (int pos = 0; pos < len - 7; pos += 8) {
xreal = buf[pos+0] - buf[pos+3] + buf[pos+7] - buf[pos+4];
yimag = buf[pos+1] - buf[pos+5] + buf[pos+2] - buf[pos+6];
Sample s( xreal << 4, yimag << 4 );
Sample s( xreal << 3, yimag << 3 );
**it = s;
(*it)++;
}
@@ -122,25 +122,29 @@ void RTLSDRThread::decimate16(SampleVector::iterator* it, const quint8* buf, qin
{
// Offset tuning: 4x downsample and rotate, then
// downsample 4x more. [ rotate: 0, 1, -3, 2, -4, -5, 7, -6]
qint16 xreal, yimag;
for (int step = 0; step < len - 31; step +=32) {
xreal = yimag = 0;
for (int pos = step; pos < step + 32; pos += 8) {
xreal += buf[pos+0] - buf[pos+3] + buf[pos+7] - buf[pos+4];
yimag += buf[pos+1] - buf[pos+5] + buf[pos+2] - buf[pos+6];
qint16 xreal[4], yimag[4];
bool b;
for (int pos = 0; pos < len - 31; ) {
for (int i = 0; i < 4; i++) {
xreal[i] = (buf[pos+0] - buf[pos+3] + buf[pos+7] - buf[pos+4]) << 4;
yimag[i] = (buf[pos+1] - buf[pos+5] + buf[pos+2] - buf[pos+6]) << 4;
pos += 8;
}
Sample s( xreal << 3, yimag << 3 );
**it = s;
Sample s1( xreal[0], yimag[0] );
Sample s2( xreal[1], yimag[1] );
Sample s3( xreal[2], yimag[2] );
Sample s4( xreal[3], yimag[3] );
m_decimator2.myDecimate(&s1, &s2);
m_decimator2.myDecimate(&s3, &s4);
m_decimator4.myDecimate(&s2, &s4);
**it = s4;
(*it)++;
}
}
/*
Decimate everything by 16x, except 288kHz
TODO : no offset tuning for direct sampling
*/
// Decimate everything by 16x, except 288kHz
void RTLSDRThread::callback(const quint8* buf, qint32 len)
{
qint16 xreal, yimag, phase;
@@ -149,14 +153,12 @@ void RTLSDRThread::callback(const quint8* buf, qint32 len)
int mode = 0;
if (m_samplerate < 800000)
mode = 2;
// if (directsampling) mode++;
switch(mode) {
case 0:
decimate16(&it, buf, len);
break;
case 1:
// no_rotate16(&it, buf, len);
break;
case 2:
@@ -164,7 +166,6 @@ void RTLSDRThread::callback(const quint8* buf, qint32 len)
break;
case 3:
// norotate4(&it, buf, len);
break;
default:
@@ -183,3 +184,4 @@ void RTLSDRThread::callbackHelper(unsigned char* buf, uint32_t len, void* ctx)
RTLSDRThread* thread = (RTLSDRThread*)ctx;
thread->callback(buf, len);
}