[mythtv] Shouldn't MythTV disable the tuner between switching inputs?

Michael T. Dean mtdean at thirdcontact.com
Sun Jan 6 03:37:38 UTC 2008


On 01/05/2008 07:42 PM, Rudy Zijlstra wrote:
> Daniel Kristjansson wrote:
>   
>> On Sat, 2008-01-05 at 15:56 -0800, Sam Logen wrote:
>>>   Anyhow, when I'm attaching a device to a/v
>>> connectors on a PVR-150, and I'd like to watch Livetv
>>> through that, instead of the tuner, I can't seem to
>>> change my inputs on the card because the tuner isn't
>>> being shut off first (I have programming on the tuner,
>>> so I want to keep that input source).  I'm just asking
>>> if it's not better to have Mythtv shut off the tuner
>>> before switching away from it to a different input.
> Are you certain on this? What i do remember is that it cannot switch 
> while encoding... In other words, the driver will refuse to switch 
> inputs while the MPEG2 engine is active, as doing that will cause 
> incorrect MPEG streams. When you switch with the MPEG engine not active, 
> there should be no problem. Can you point to the relevant ivtv posting?
>   
>> Historically the ivtv driver has not had a problem with switching
>> inputs. Do you have any information on when the driver was changed
>> and do you know if this only applies to the PVR-150 or the whole
>> range of ivtv cards? Turning off the tuner would introduce a channel
>> changing delay for all MPEG-2 recording cards and turning on and off
>> the tuner when special hardware requires it is really a job for
>> the driver anyway, we shouldn't need to special case for particular
>> hardware or particular V4L2 drivers in MythTV; we don't really have
>> enough information, and that taking care of that stuff is the main
>> reason we bother with drivers in the first place for an application
>> like MythTV.
>>
>> FYI I'm stuck using an older ivtv since the current drivers, starting
>> a little before 1.0.0, don't support 608 captions on PVR-250 cards.

In other words, it sounds like the OP needs to set up a video source 
(i.e. "External", grabber set to "No grabber") with one channel (i.e. 
channel 999, callsign "EXT", channel change script /bin/true) and 
connect it to the "a/v connectors" (Composite/S-Video? inputs) and /let 
Myth manage changing inputs for him/ rather than doing it manually 
through the command line without Myth's permission.

Mike


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