[mythtv-users] Seek Table Question

Tony Lill ajlill at ajlc.waterloo.on.ca
Fri Jun 8 03:19:04 UTC 2007


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.
--
Tony Lill,                         Tony.Lill at AJLC.Waterloo.ON.CA
President, A. J. Lill Consultants        fax/data (519) 650 3571
539 Grand Valley Dr., Cambridge, Ont. N3H 2S2     (519) 241 2461
--------------- http://www.ajlc.waterloo.on.ca/ ----------------

Understatement of the century:
"Hello everybody out there using minix - I'm doing a (free) operating
 system (just a hobby, won't be big and professional like gnu) for
 386(486) AT clones"

	- Linus Torvalds, August 1991



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