Re: [PATCH 0/1] xc3028: force reload of DTV7 firmware in VHF band with Zarlink demodulator

[Mauro Carvalho Chehab <mchehab@redhat.com>]

On 07-12-2011 17:31, Gianluca Gennari wrote:

> thanks a lot for the detailed explanation, but it is not needed anymore.
> I think I got it: reading the comments in the code and in particular a
> couple of weird "hacks", I think I figured out what is going on.
>
> I have prepared a patch that fixes center frequency adjustment:
> basically, this let us get rid of this weird code:
>
>
> 		if ((priv->cur_fw.type&  DTV78)&&  freq<  470000000)
> 			offset -= 500000;
>
> which assumes all channels below 470000000 have 7MHz bw.
>
> Also we can get rid of this adjustment that seems to come out of nowhere:
>
> 		if (priv->cur_fw.type&  DTV7)
> 			offset += 500000;
>
> Maybe those hacks where necessary for old firmwares, but the updated
> ones (a comment mentions updates SCODE tables, whatever this means)
> seems to use the same center frequency value for all bandwidths and all
> firmwares (well, at least DTV7, DTV8 and DTV78; we will never know about
> DTV6).

Old firmwares behave like newer ones, AFAIK. DTV78 is there since at least
firmware v2.2.

>
> I tested this patch with all firmwares:
> DTV7 ->  OK in VHF band
> DTV8 ->  OK in UHF band
> DTV78 ->  OK in both VHF and UHF
>
> Please note also that the patch is not changing anything for DTV7 and
> DTV8 firmwares. The only thing really affected is the center frequency
> calculation for DTV78 firmware in VHF band.
>
> What do you think about it?

It makes sense. The offset adjustment should be done based on the bandwidth
and if the firmware is either DTV78 or DTV7/DTV8, and not based on the frequency.

> By the way, DVB-T tables from dvb-apps are really outdated, and anyway
> they are completely useless in Italy. Here we have a jungle of
> frequencies (about 50 in my area), which are
> appearing/disappearing/changing some modulation parameter almost every
> day, and also if you move a few km away you will probably get some
> different ones.
> So no table will be ever up-to-date, and even if it is, it will be only
> useful to the person who created it. Maybe in a year or two the
> situation will stabilize (after the switch-off is completed everywhere),
> but until then it's a mess.

It would be nice to at least fix the auto-italy table, in order for it to match
whatever Italy channel frequencies are in use, currently.

>
> Best regards,
> Gianluca

Regards,
Mauro