[mythtv-users] Playback problem -- random short pauses

[Don Lewis]

On 22 May, Steven Adeff wrote:
> On Sun, May 22, 2011 at 11:01 PM, Jean-Yves Avenard <jyavenard at gmail.com> wrote:
>> On 23 May 2011 12:49, Steven Adeff <adeffs.mythtv at gmail.com> wrote:
>>> does your video stutter too?
>>
>> it's not noticeable by much ; can only see it in the logs that
>> something went amiss. My amplifier takes a while to resync over hdmi
>> audio ; so this it where I notice it the most (and because I'm so
>> acute to audio problems)
>>
>>> how much ram do you have?
>> 4GB
>>> how fast is the drive your sql database is on?
>>
>> It's a samsung 7200 RPM 1TB disk.
>>
>> No known issues.
>>
>> Jean-Yves
> 
> I'm thinking it may be a SQL access speed issue. increasing the HD
> buffers don't seem to fix it, and it only seems to be an issue with
> recordings. I also notice that if you rewind and play that section
> again it will be fine, so it's not the recording in any specific way.
> 
> I'm wondering if you were to decrease your available memory if the
> pauses will get longer. I'm currently thinking of maxing my backend
> motherboard to 4GB (I'm at 3 now) and see what that does to my minor
> stutter. My parents system has a slightly worse stutter, only 2GB of
> ram, want to try increasing theirs as well and see if that helps.

I've had the same problem ever since I upgraded my FE/BE from 0.23 to
0.24. The playback pauses are correlated with the backend starting
and/or finishing a recording.  The picture just freezes and the sound
just stops.  In my case it can be for a couple of seconds.

I've got a bunch of drives in a JBOD configuration, so I/O bandwith
shouldn't be an issue and the problem even occurs with a single SD
recording.  When separate disks are being used for viewing and recording
I don't see any difference.

The first thing I tried was upgrading from a dual core CPU to a triple
core CPU, and that didn't make a difference.  Even with the dual core
CPU, total CPU usage was pretty low, but I figured that adding another
core might help with scheduling issues.  I tuned comflagging to be less
of a CPU hog and that didn't make a difference.  I was running Fedora 12
in 32 bit mode and RAM was already maxed out at 4 GB. It looked to me
like mysqld could use more RAM, so I ugpraded to Fedora 14 x86_64 and
bumped the RAM to 8 GB so that I could crank up some of the mysqld
knobs. mysqltuner.pl doesn't find significant problems. Running
optimize_mythdb.pl doesn't seem to help. The root filesystem and
database reside on a dedicated Samsung HD502HJ 7200 RPM 500 GB drive.