mythbackend logs RingBuf-messages every few seconds while playing LiveTV

[kenni]

After upgrading from 0.24-fixes to master/0.25, the backend continuously writes out RingBuf? log messages about it waiting for data:

mythbackend[9601]: RingBuf(/data/mythtv/livetv/1001_20120310153618.mpg): Waited 1.0 seconds for data #012#011#011#011to become available... 130980 < 196608

While it does this, LiveTV works fine with no stuttering. The issue seems consistent on all channels in LiveTV and playing back recordings does NOT give the RingBuf? logs. Eg. playing back any recording - even the just-recorded LiveTV recording from the recordings menu - does NOT cause the backend to write out these messages.

Logs from ~5 minutes of LiveTV playback is attached. If more verbose logs are required to identify the issue, I'll be happy to provide them.

The tuner is a European HDHR dual DVB-C tuner. The backend is a 3.4GHz Core i5 with 12GB RAM and database+OS on a SSD, so it seems unlikely that this is a local performance issue.

[kenni]

I forgot to add that disabling barriers on the ext4 file systems have no impact on the issue.

[danielk]

I think perhaps we are reading too close to the end of the file.

Does this occur if you skip back a few seconds after LiveTV starts?

i.e. start Live TV, wait 5 seconds, hit the back arrow. Do any new RingBuffer? messages occur in the next minute or so?

[kenni]

Log illustrating the issue while skipping back and forward

[kenni]

Heh, this is interesting :) When I start LiveTV the playback is 4-5 seconds behind according to the OSD. If I skip back once, it's 10-11 seconds behind, but still spits out the log-messages with the same rate as before. If I skip back once more, it is now 15-16 seconds behind and the log-messages disappear completely. I've uploaded a new log file, mythbackend_log_while_skipping.log, which illustrates this behaviour.

[Daniel Thor Kristjansson <danielk@…>]

In 483e06f6b8a9066f66cef3fcf0a5f844519f51f9/mythtv:

Refs #10428. Fix off-by-1000 error in RingBuffer?.

The estimated bit rate is in kilobits not bits...

Also increase the seconds of buffering from 0.25 to 0.35
for a better LiveTV experience.

[JoeB@…]

Hi danielk,

How do we apply this fix? Will it be in an update upstream in the MythTV PPA repository or do we have to do any configuration?

Thanks,

JoeB.

[kenni]

JoeB, please use the mythtv-users mailing list for questions, not our bugtracker. The commit has been committed to master/pre0.26, and it will therefore at least be part of the soon-to-be-released MythTV 0.26. The commit might be backported to 0.25-fixes, if so, you'll see the 0.25-fixes commit here and you should be able to pick it up from the Mythbuntu autobuilds.

[danielk]

Fixed by [483e06f6b8a].