Try setting Gain & Bandwidth.

plugins/channel/CMakeLists.txt

@@ -1,7 +1,7 @@
 project(demod)
 
 add_subdirectory(lora)
-add_subdirectory(nfm_testing)
+add_subdirectory(nfm)
 add_subdirectory(ssb)
 add_subdirectory(tcpsrc)
 add_subdirectory(usb)

plugins/samplesource/v4l-msi/v4linput.cpp

@@ -26,13 +26,13 @@ MESSAGE_CLASS_DEFINITION(V4LInput::MsgConfigureV4L, Message)
 MESSAGE_CLASS_DEFINITION(V4LInput::MsgReportV4L, Message)
 
 V4LInput::Settings::Settings() :
-	m_gain(0)
+	m_gain(6)
 {
 }
 
 void V4LInput::Settings::resetToDefaults()
 {
-	m_gain = 0;
+	m_gain = 6;
 }
 
 QByteArray V4LInput::Settings::serialize() const
@@ -53,7 +53,7 @@ bool V4LInput::Settings::deserialize(const QByteArray& data)
 	}
 
 	if(d.getVersion() == 1) {
-		d.readS32(1, &m_gain, 0);
+		d.readS32(1, &m_gain, 6);
 		//d.readS32(2, &m_samplerate, 0);
 		return true;
 	} else {

plugins/samplesource/v4l-msi/v4lsource.cpp

@@ -64,7 +64,6 @@ static void xioctl(int fh, unsigned long int request, void *arg)
 void
 V4LThread::OpenSource(const char *filename)
 	{
-		struct v4l2_format fmt;
 		struct v4l2_buffer buf;
 		struct v4l2_requestbuffers req;
 		enum v4l2_buf_type type;
@@ -81,14 +80,17 @@ V4LThread::OpenSource(const char *filename)
 		// sampletype depends on samplerate. Set that first
 		set_sample_rate( (double)SAMPLERATE );
 		set_center_freq( (double)centerFreq );
-
+		set_bandwidth( (double)IF_BANDWIDTH );
+		set_tuner_gain( (double) 6.0);
+#if 0
+		struct v4l2_format fmt;
 		pixelformat = V4L2_PIX_FMT_SDR_CS14LE;
 		CLEAR(fmt);
 		fmt.type = V4L2_BUF_TYPE_SDR_CAPTURE;
 		fmt.fmt.sdr.pixelformat = pixelformat;
-		xioctl(fd, VIDIOC_G_FMT, &fmt);
+		xioctl(fd, VIDIOC_S_FMT, &fmt);
 		qCritical(" Expecting format CS14LE, got : %4.4s", (char *)&fmt.fmt.sdr.pixelformat);
-
+#endif
 		CLEAR(req);
 		req.count = 8;
 		req.type = V4L2_BUF_TYPE_SDR_CAPTURE;
@@ -232,30 +234,28 @@ V4LThread::work(int noutput_items)
 	unsigned int pos = 0;
 	// MSI format is 252 sample pairs :( 63 * 4) * 4bytes
 	it = m_convertBuffer.begin();
-	if (recebuf_len >= 8) { // in bytes
+	if (recebuf_len >= 16) { // in bytes
 		b = (uint16_t *) recebuf_ptr;
 		unsigned int len = 8 * noutput_items; // decimation (i+q * 4 : cmplx)
 		if (len * 2 > recebuf_len)
 			len = recebuf_len / 2;
 		// Decimate by four for lower cpu usage
-		// ??? seems to have gone a bit wrong.
+		for (pos = 0; pos < len - 7; pos += 8) {
-		for (pos = 0; pos < len - 3; pos += 4) {
+			xreal = CASTUP(b[pos+0]<<2) + CASTUP(b[pos+2]<<2)
-			xreal = CASTUP(b[pos+0]<<2) + CASTUP(b[pos+1]<<2)
+				+ CASTUP(b[pos+4]<<2) + CASTUP(b[pos+6]<<2);
-				+ CASTUP(b[pos+2]<<2) + CASTUP(b[pos+3]<<2);
+			yimag = CASTUP(b[pos+1]<<2) + CASTUP(b[pos+3]<<2)
-			yimag = 0;
+				+ CASTUP(b[pos+5]<<2) + CASTUP(b[pos+7]<<2);
-				//CASTUP(b[pos+1]<<2) + CASTUP(b[pos+3]<<2)
-				//+ CASTUP(b[pos+5]<<2) + CASTUP(b[pos+7]<<2);
 			Sample s( (qint16)(xreal >> 2) , (qint16)(yimag >> 2) );
 			*it = s;
 			it++;
 		}
 		m_sampleFifo->write(m_convertBuffer.begin(), it);
 		recebuf_len -= pos * 2; // size of int16
-		recebuf_ptr = (void*)(b + pos);	
+		recebuf_ptr = &b[pos];
 	}
 	// return now if there is still data in buffer, else free buffer and get another.
-	if (recebuf_len >= 8)
+	if (recebuf_len >= 16)
-		return pos / 4;
+		return pos / 8;
 	{	// free buffer, if there was one.
 		if (pos > 0) { 
 			CLEAR(buf);
@@ -292,5 +292,5 @@ V4LThread::work(int noutput_items)
 		recebuf_len = buf.bytesused;
 		recebuf_mmap_index = buf.index;
 	}
-	return pos / 4;
+	return pos / 8;
 }

plugins/samplesource/v4l-msi/v4lthread.h

@@ -26,6 +26,7 @@
 
 // lowest samplerate in the kernel is 1.2M, but this works better
 #define SAMPLERATE 1536000
+#define IF_BANDWIDTH 300000
 #define BLOCKSIZE 8192
 
 class V4LThread : public QThread {