[mythtv-users] LiveTV glitches at program transitions (was Re: [mythtv] mythplayer.cpp query)

Raymond Wagner raymond at wagnerrp.com
Wed Mar 14 11:05:25 UTC 2012


On 3/14/2012 06:41, Russell Gower wrote:
> On 14 Mar 2012, at 10:10, Terjesen Jens Peder wrote:
>
>> 2012-03-13 09:15:01.343816 I  Player(0): SwitchToProgram - start
>>
>> <snip>
>>
>> 2012-03-13 09:15:01.525242 N  SG(LiveTV): Unable to find storage group 'LiveTV', trying 'Default' group!
>> 2012-03-13 09:15:01.530305 I  ProgramInfo(8441_20120313091500.mpg): GetPlaybackURL: File is local: '/mythtv/kvm02/Recordings/8441_20120313091500.mpg'
>> 2012-03-13 09:15:01.530322 I  FileRingBuf(/mythtv/kvm02/Recordings/8441_20120313083045.mpg): OpenFile(/mythtv/kvm02/Recordings/8441_20120313091500.mpg, 10000 ms)
>> 2012-03-13 09:15:01.535417 I  AO: OutputAudioLoop: audio paused
>> 2012-03-13 09:15:05.544482 I  FileRingBuf(/mythtv/kvm02/Recordings/8441_20120313091500.mpg): OpenFile() made 346 attempts in 4014 ms
>>
>> <snip>
>>
>> 2012-03-13 09:15:05.610378 I  RingBuf(/mythtv/kvm02/Recordings/8441_20120313091500.mpg): safe_read(... at 0, 1048576) ->  349116, took 66 ms (42.3171Mbps)
>>
>> <snip>
>>
>> 2012-03-13 09:15:05.675579 I  RingBuf(/mythtv/kvm02/Recordings/8441_20120313091500.mpg): safe_read(... at 349116, 1048576) ->  0, took 60 ms (0Mbps)
>>
>> <snip>
>>
>> 2012-03-13 09:15:05.981138 I  RingBuf(/mythtv/kvm02/Recordings/8441_20120313091500.mpg): safe_read(... at 349116, 1048576) ->  0, took 301 ms (0Mbps)
>> 2012-03-13 09:15:06.237066 I  RingBuf(/mythtv/kvm02/Recordings/8441_20120313091500.mpg): Waited 0.2 seconds for data
> I've taken this to the user list as it doesn't appear to be a development issue at this stage.
>
> After my last post I started digging into the OpenFile() 4014ms issue, as Jens said it appears than the backend is having storage issues, I'm going to setup a separate combinded BE/FE test system for further analysis.
>
> At this stage I believe the "Waited 0.2 seconds for data" are due to the frontend reading to close to the end of the file, if playback is paused for a few seconds they go away.

May as well forward the request over there then...

It looks like roughly 7.1 of that 7.6 seconds is sitting there waiting 
for the data to get written to your filesystem. If the data isn't 
available for the frontend to read it, then nothing you change in the 
frontend is going to make the slightest bit of difference. We need to 
see backend logs to see where the actual stall is.

We also need to know more about how your system is actually configured. 
Looking through the mailing list archives, you appear to be running 
independent frontends, which means if you are reading off the 
filesystem, you are reading over NFS. Is it possible your problem is 
caused by nothing more than NFS caching issues that would be resolved by 
merely not mounting those disks and letting MythTV stream its content 
internally?



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