stv0297: QAM256 improvement for TT-C2300 revisited

linux-dvb Alexander Koenig 1 participant 1 message Jul 31, 2008 Media (V4L/DVB)

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Alexander Koenig

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2008-07-31 20:47 UTC #0 lore raw

Hi,

last October Hartmut Birr submitted a patch that greatly improves reception of QAM256 modulated channels on the TT-C2300.
(http://www.linuxtv.org/pipermail/linux-dvb/2007-October/021422.html)

The patch was not applied as there were a few reports that it was causing problems. However, the end of the thread suggests that some of these issues were a result of using the patch in combination with other frequency shifting patches that also tried to address QAM256 issues.

Other issues were reported on different hardware (CableStar), so I extended the patch to change the demodulation frequency only for Nexus-CA.

The patch was tested successfully on two TT-C2300 based systems, it would be great if someone could test whether the patch does hurt QAM256 reception with CableStar devices or not.

Alexander König

linux/drivers/media/dvb/frontends/stv0297.c +3 -1

diff -ru v4l-dvb.org/linux/drivers/media/dvb/frontends/stv0297.c v4l-dvb/linux/drivers/media/dvb/frontends/stv0297.c
@@ -463,7 +463,9 @@
 	stv0297_writereg(state, 0x82, 0x0);
 
 	/* set initial demodulation frequency */
-	stv0297_set_initialdemodfreq(state, 7250);
+	stv0297_set_initialdemodfreq(state, 
+		state->config->qam256_reduced_demodfreq & 
+		(p->u.qam.modulation == QAM_256) ? 6718 : 7250);
 
 	/* setup AGC */
 	stv0297_writereg_mask(state, 0x43, 0x10, 0x00);

linux/drivers/media/dvb/frontends/stv0297.h +5 -0

diff -ru v4l-dvb.org/linux/drivers/media/dvb/frontends/stv0297.h v4l-dvb/linux/drivers/media/dvb/frontends/stv0297.h
@@ -40,6 +40,11 @@
 
 	/* set to 1 if the device requires an i2c STOP during reading */
 	u8 stop_during_read:1;
+
+	/* set to 1 if the device requires reduced demodulation frequency 
+	* for QAM256.
+	*/
+	u8 qam256_reduced_demodfreq:1;
 };
 
 #if defined(CONFIG_DVB_STV0297) || (defined(CONFIG_DVB_STV0297_MODULE) && defined(MODULE))

linux/drivers/media/dvb/ttpci/av7110.c +1 -0

diff -ru v4l-dvb.org/linux/drivers/media/dvb/ttpci/av7110.c v4l-dvb/linux/drivers/media/dvb/ttpci/av7110.c
@@ -1874,6 +1874,7 @@
 	.inittab = nexusca_stv0297_inittab,
 	.invert = 1,
 	.stop_during_read = 1,
+	.qam256_reduced_demodfreq = 1,
 };

linux/drivers/media/dvb/ttpci/budget-ci.c +1 -0

diff -ru v4l-dvb.org/linux/drivers/media/dvb/ttpci/budget-ci.c v4l-dvb/linux/drivers/media/dvb/ttpci/budget-ci.c
@@ -1061,6 +1061,7 @@
 	.inittab = dvbc_philips_tdm1316l_inittab,
 	.invert = 0,
 	.stop_during_read = 1,
+	.qam256_reduced_demodfreq = 0,
 };
 
 static struct tda10023_config tda10023_config = {

linux/drivers/media/dvb/ttusb-budget/dvb-ttusb-budget.c +1 -0

diff -ru v4l-dvb.org/linux/drivers/media/dvb/ttusb-budget/dvb-ttusb-budget.c v4l-dvb/linux/drivers/media/dvb/ttusb-budget/dvb-ttusb-budget.c
@@ -1572,6 +1572,7 @@
 	.demod_address = 0x1c,
 	.inittab = dvbc_philips_tdm1316l_inittab,
 	.invert = 0,
+	.qam256_reduced_demodfreq = 0,
 };
 
 static void frontend_init(struct ttusb* ttusb)

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