[mythtv-users] Help with playback issue on recordings from a single channel

Vincent Poore vincepoore at yahoo.com
Wed Dec 29 23:52:23 UTC 2021

 I really don't think my hardware has issues as in it's faulty.   I think my hardware AMD A10-5800K APU 3.8Ghz 4 Core Processor with integrated Trinity Radeon HD 7660D graphics is sensitive to something unique about the bad channel's recordings / broadcast encoding.
Doesn't common sense say if it were faulty hardware, most or all of my recordings would have an issue not just 1 channel out of more than 50 different channels I watch.
Doesn't common sense say that if it was all working perfectly on all channels for nearly 3 years until the day the station engineer made some encoding changes, the change exposed some hardware/software bug only impacted by my particular hardware.
That said, I will do more tests to rule out those faults eventually.  Things like trying the ffmeg on a different channel's recording (I predict it will be fine).   Things like monitoring the CPU temp while the ffmpeg is running on the bad channel (I predict the temp will be fine).  
So far nobody has responded who is using an AMD processor for both compute and graphics.

    On Wednesday, December 29, 2021, 03:51:29 PM MST, Klaas de Waal <klaas.de.waal at gmail.com> wrote:  

On Wed, 29 Dec 2021 at 03:17, Vincent Poore via mythtv-users <mythtv-users at mythtv.org> wrote:

 I'm replying to myself on this to summarize everything so far and shift the focus of my original query.
Thank you to everyone who replied.   I'm grateful for all the input from everyone.
In the beginning I was hopeful someone would recognize this and say "have the station engineer change x on the encoding and problem will be resolved."   I've kind of lost hope of having the station fix something on their end and I pretty much have to deal with this in MythTV.
At this point, it's not so bad having to use Open GL High Quality to view the recordings.   The inability to skip backwards 10 seconds is what stinks.    At first I was hopeful that mythcommflag --rebuild would at least help out, but that has made things worse.   When I run that, I can't view the recording at all.  It just skips directly to the end on initial playback.    Also this work-around was never going to help out when viewing a slightly delayed live recording like a football game.
If we forget about hardware accelerated playback, is there anything I can do to mitigate the skip backwards problem?   I have two other front ends that also playback fine except for the skip backwards issue.
I'm going to start looking at and experimenting with the recordedseek table.  Maybe if I remove all seek info for a recording it will behave better than having bad seek info?
Is there anyone expert at how seek info is populated in order to render a guess as to what is going on?   It seems like the best chance for resolution is to figure out how the recording is throwing off the seek calculations.

I think that in the summary you do miss the most important thing and that is that your hardware has issues. It should at the very least be capable of completing the ffmpeg transcode. Other good tests are memcheck68 (can sometimes be selected at boot) and a compilation of MythTV from source using all cores. Or, even better, the Linux kernel.It could be a thermal issue as Stephen suggested; to verify that you can run the sensors command repeatedly (e.g. "watch -n1 sensors" ) while the ffmpeg transcode is running. If it is a thermal problem then the temperature will increase to at least 100 degrees before the CPU locks.However, my best guess is that your motherboard is faulty and I suggest reproducing the problem on known good hardware. It is not possible to do software problem analysis on faulty hardware.
About the skipping problem. It could be that there is something in the stream that causes bad data in the recordedseek table and that then causes the skipping issues.However, if that is the problem then after a rebuild with "mythcommflag --rebuild" as you have done then skipping should be OK.
Hope this helps,Klaas.
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