[mythtv-users] Wrong Channel when recording?

Roger Martensson roger.martensson at gmail.com
Thu May 14 15:48:07 UTC 2015


Den 14 maj 2015 17:17 skrev "Mike Perkins" <mikep at randomtraveller.org.uk>:
>
> On 14/05/15 11:54, Hika van den Hoven wrote:
>>
>> Hoi Mike,
>>
>> Thursday, May 14, 2015, 11:17:35 AM, you wrote:
>>
>>> On 13/05/15 23:25, John Pilkington wrote:
>>>>
>>>> On 13/05/15 22:51, Hika van den Hoven wrote:
>>>>>
>>>>> Hoi Eric,
>>>>>
>>>>> Wednesday, May 13, 2015, 11:25:55 PM, you wrote:
>>>>>
>>>>>> On Wed, May 13, 2015 at 5:02 PM, Hika van den Hoven <
hikavdh at gmail.com> wrote:
>>>>>>>
>>>>>>> I did some checking and I can't find a way to set a channel as HD or
>>>>>>> SD. Only individual programs can be marked as HD by your grabber.
>>>>>
>>>>>
>>>>>> That's right.
>>>>>
>>>>>
>>>>>>> Which is weird. Why then that filter. and isn't everything on a
>>>>>>> channel either SD or HD?
>>>>>
>>>>>
>>>>>> Not exactly.  An "HD" channel may broadcast in 1080i content that was
>>>>>> upscaled from 480i.  Is that content HD or SD?  The listing (if
>>>>>> correct) should list that program as SD even if it's on an "HD"
>>>>>> channel.  The idea is that MythTV should be able to record SD
>>>>>> broadcasts of SD content and do its own upscaling (if needed), but my
>>>>>> experience has been that the listings are horribly inaccurate to the
>>>>>> point of uselessness wrt determining which programs are actually HD.
>>>>>> This was why I deleted all of the SD channels.  Too many listings
>>>>>> listed HD programs as not-HD.
>>>>>
>>>>>
>>>>>> Eric
>>>>>> _______________________________________________
>>>>>
>>>>>
>>>>> So, for the filter to work, you need different listings for the two
>>>>> channels: For the HD channel with the <video><HD> tag's where
>>>>> appropriate and without the tags for the SD channel.
>>>>>
>>>>> It would be nice if you could tag a channel as HD or SD and that
>>>>> mythfilldatabase would ignore the HD tags for an SD channel! I'm now
>>>>> thinking of a way to handle this in my grabber.
>>>>
>>>>
>>>> Is this another instance of the need to switch some recent device
drivers
>>>> explicitly for HD or SD?  AIUI myth doesn't at present do that - see
#12342.  I
>>>> think I would expect an attempt to record HD without such a switch to
fail
>>>> because the PIDs were wrong, but...
>>>>
>>> Switching from SD to HD is a bit more fundamental than that, at least
in the UK.
>>> Scanning with my SD USB tuners doesn't even recognise the existence of
the HD
>>> multiplex.
>>
>>
>>> I'm guessing the drivers have to switch to a whole different tuning
mode to
>>> change between SD and HD and it is this that is currently not happening
correctly.
>>
>>
>>> Just sending a command "Tune to multiplex x, subchannel y" works between
>>> channels that are all SD, or all HD, but a little extra is needed
changing
>>> transmission protocols - and recognising that you need to do so.
>>
>>
>> If so, how does MythTV know? There is nothing in the db to indicate
>> wether a channel is HD, SD or radio. And here they are all mixed
>> together. I guess in my case, since I have a HDhomerun, the tuning is
>> done by the HDhomerun and MythTV can just sample the stream, but how
>> with a pci-e or usb tuner?
>>
> Looks like we have some confusion here because of different practices in
different countries.
>
> In the UK case, HD is at the moment only transmitted as h264 on DVB-T2
while SD and radio are transmitted as MEPG2 on DVB-T. As far as I know the
two are never mixed. Radio is tricky since there is no (or very little)
video component and myth is unsure how to process it. (TV manages to do it
fine.)
>

Same here in Sweden. To see HD material you need a tuner that support
DVB-T2.
But I'm on digital cable, DVB-C.

Newer kernels have some support for this. When upgrading kernel last year I
had to add a command in the startup that switches my drivers default of
DVB-T to DVB-C since myth doesn't have support for it currently.

> As for how mythtv knows the difference, I have no idea. I always assumed
that some parameter in the multiplex table would indicate the method used
to tune it.
>
> --
>
> Mike Perkins
>
>
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