On Sun, 2009-05-31 at 10:22 -0300, Mauro Carvalho Chehab wrote:
> Em Sun, 31 May 2009 08:41:43 -0400
> Andy Walls <awa...@radix.net> escreveu:
>
> > This is a patch with changes provided by Terry Wu to support 6 MHz DVB-T
> > as is deployed in Taiwan.
> >
> >
> > I took quick look at the changes and they look OK to me, but I'm no
> > expert on the XC2028/XC3028 deivces.
> >
> > My one observation is that the change assumes all COFDM frontends can
> > support QAM (FE_CAN_QAM..). This is apparently the case looking through
> > all the Linux supported FE_OFDM frontends, and it seems like a
> > reasonable assumption to me.
> >
> >
> > Terry,
> >
> > Please check the diff below, to make sure I captured all your changes.
> >
> > For inclusion into the kernel, you will need to provide a
> > "Signed-off-by:" in a rely to this patch list posting. Please see:
> >
> > http://www.linuxtv.org/wiki/index.php/Development:_Submitting_Patches#Developer.27s_Certificate_of_Origin_1.1
> >
> >
> > Regards,
> > Andy
> >
> >
> > diff -r 8291f6042c9a linux/drivers/media/common/tuners/tuner-xc2028.c
> > --- a/linux/drivers/media/common/tuners/tuner-xc2028.c Fri May 29
> > 21:19:25 2009 -0400
> > +++ b/linux/drivers/media/common/tuners/tuner-xc2028.c Sun May 31
> > 08:29:32 2009 -0400
> > @@ -925,6 +925,9 @@
> > rc = send_seq(priv, {0x00, 0x00});
> > } else if (priv->cur_fw.type & ATSC) {
> > offset = 1750000;
> > + } else if (priv->cur_fw.type & DTV6) {
> > + /* For Taiwan DVB-T 6 MHz bandwidth - Terry Wu */
> > + offset = 1750000;
>
> This is wrong, since it will break xc3028 for all other DVB-T standards.
> The offset depends on the demod type. He probably choose the wrong IF for the
> demod.
>
> Terry, please provide your boards entry for us to help you to properly set it.
> > } else {
> > offset = 2750000;
> > /*
> > @@ -1026,6 +1029,11 @@
> > switch(fe->ops.info.type) {
> > case FE_OFDM:
> > bw = p->u.ofdm.bandwidth;
> > + /* For Taiwan DVB-T 6 MHz bandwidth - Terry Wu */
> > + if (bw == BANDWIDTH_6_MHZ) {
> > + type |= (DTV6|QAM|D2633);
> > + priv->ctrl.type = XC2028_D2633;
> > + }
>
> Hmm... why are you asking for the QAM firmware here? Shouldn't it be at
> FE_QAM?
I think I can provide a little insight:
They way I understood things is that DVB-T demodulators (like the
ZarLink used for the DTV1800 - zl10353 driver) are always of type
FE_OFDM. The OFDM subcarriers for DVB-T can be modulated with QPSK or
QAM (I think there is a hierarchical modulation scheme - I have to do
more reading).
In the Linux dvb frontend drivers, the FE_QAM type is used for only for
cable TV (DVB-C) frontends.
My questions:
Is OFDM used for other Digital TV aside from DVB-T?
Does the XC20208 have firmware explcitily for OFDM irrespective of the
subcarrier modulation?
Here is a list of DVB deployment reports:
http://www.dvb.org/dvb-deployment-data.xls
Columns Q, R and U show these countries as DVB-T in a 6 MHz bandwidth
Taiwan: ~8000 subcarriers, 16 QAM
Uruguay: ~2000 subcarriers, 16 QAM and 64 QAM
So both of the currently deployed DVB-T systems using 6 MHz use QAM
subcarriers.
The only deployments using QPSK are using it in an 8 MHz bandwidth for
mobile services.
All the DVB demods in the v4l-dvb source tree that are FE_OFDM are
marked FE_CAN_QAM_{16,64,AUTO}, except in
v4l-dvb/linux/drivers/media/dvb/frontends/cx22700.c
the CX22700 is not marked FE_CAN_QAM_AUTO.
Regards,
Andy
> This will also break for other countries with 6 MHz bw. Also, priv->ctrl
> should
> be set inside your board definitions.
>
> Could you please provide us more info about the DVB-T standard in Taiwan?
>
> > break;
> > case FE_QAM:
> > tuner_info("WARN: There are some reports that "
> >
> >
>
>
>
>
> Cheers,
> Mauro
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