[mythtv-users] Seek Table Question

Brian L. Walter blwalter at gmail.com
Fri Jun 8 10:35:57 UTC 2007


Tony Lill wrote:
> Brian Walter <blwalter at gmail.com> writes:
>
>   
>> Bryan Mayland wrote:
>>     
>>> Brian Walter wrote:
>>>   
>>>       
>>>> I noticed when running a mythcommflag --rebuild on my video directory,
>>>> that it appears sql statements are queued up, then posted en mass (this
>>>> is from watching the progress bar, as well as watching 'top' on the sql
>>>> server).
>>>>
>>>> Is this the same behavior mythbackend uses while recording a program?
>>>>   
>>>>     
>>>>         
>>> Depends on which recorder is being used.  I know that the mpeg2recorder 
>>> (used for PVR-150/500/250/350 capture) flushes the "position map" to the 
>>> database every 30 keyframes, and every 5 for the 30.
>>> _______________________________________________
>>>   
>>>       
>> Thanks!  just out of curiosity, *approx* how often do key frames come 
>> along?  Give this information, I'm noticing that little *burps* seem to 
>> happen in some recordings at regular intervals - usually between 10-13 
>> seconds.  The corruption is in the file - not playback, so I'm looking 
>> form something that happens on a fairly regular basis.
>> _______________________________________________
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>>     
>
> This sounds like a known issue (1660) with database updates in
> mythtv. If you're using ivtv, the driver will log a useful error
> message about dropping buffers 'cause the application is too
> slow. Other encoders probably just silently drop frames.
>
> The ticket has patches for 0.20 and the head that fix it for me and
> others. The developers are going in another direction to fix it, I
> don't know if anything's been committed to the head yet.
>
> If you're recording HD, there's a read-ahead buffer and you can tune
> the size somewhere under the settings menus. Turning it up may get you
> over the datase burps if your encoder uses it.
>   
Thanks!  That actually makes sens.  I do get the occasional 'dropping 
data' message, not as much now that I've cut back on the schedules 
running on the PVR's.

I'm unclear from comment about the patch number - is this still just in 
the trunk, or, is it in -fixes?  I'm currently running -fixes from about 
a week ago...

Brian


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