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
diff -ru v4l-dvb.org/linux/drivers/media/dvb/frontends/stv0297.c v4l-dvb/linux/drivers/media/dvb/frontends/stv0297.c
--- v4l-dvb.org/linux/drivers/media/dvb/frontends/stv0297.c 2008-07-26 18:14:23.000000000 +0200
+++ v4l-dvb/linux/drivers/media/dvb/frontends/stv0297.c 2008-07-26 18:16:38.000000000 +0200
@@ -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);
diff -ru v4l-dvb.org/linux/drivers/media/dvb/frontends/stv0297.h v4l-dvb/linux/drivers/media/dvb/frontends/stv0297.h
--- v4l-dvb.org/linux/drivers/media/dvb/frontends/stv0297.h 2008-07-26 18:14:23.000000000 +0200
+++ v4l-dvb/linux/drivers/media/dvb/frontends/stv0297.h 2008-07-26 18:16:38.000000000 +0200
@@ -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))
diff -ru v4l-dvb.org/linux/drivers/media/dvb/ttpci/av7110.c v4l-dvb/linux/drivers/media/dvb/ttpci/av7110.c
--- v4l-dvb.org/linux/drivers/media/dvb/ttpci/av7110.c 2008-07-26 18:14:23.000000000 +0200
+++ v4l-dvb/linux/drivers/media/dvb/ttpci/av7110.c 2008-07-26 18:16:38.000000000 +0200
@@ -1874,6 +1874,7 @@
.inittab = nexusca_stv0297_inittab,
.invert = 1,
.stop_during_read = 1,
+ .qam256_reduced_demodfreq = 1,
};
diff -ru v4l-dvb.org/linux/drivers/media/dvb/ttpci/budget-ci.c v4l-dvb/linux/drivers/media/dvb/ttpci/budget-ci.c
--- v4l-dvb.org/linux/drivers/media/dvb/ttpci/budget-ci.c 2008-07-26 18:14:23.000000000 +0200
+++ v4l-dvb/linux/drivers/media/dvb/ttpci/budget-ci.c 2008-07-26 18:16:38.000000000 +0200
@@ -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 = {
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
--- v4l-dvb.org/linux/drivers/media/dvb/ttusb-budget/dvb-ttusb-budget.c 2008-07-26 18:14:23.000000000 +0200
+++ v4l-dvb/linux/drivers/media/dvb/ttusb-budget/dvb-ttusb-budget.c 2008-07-26 18:16:38.000000000 +0200
@@ -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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