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

Stephen Worthington stephen_agent at jsw.gen.nz
Mon Dec 27 01:53:55 UTC 2021

On Sun, 26 Dec 2021 15:16:01 +0000 (UTC), you wrote:

> So yesterday was not a good day to lock up my machine so I didn't test ffmpeg on the sample I uploaded.   Honestly I was worried 6 minutes wasn't going to be enough but I tried it today and it did lock up my machine about three or four minutes in.  I got impatient and switched away from terminal while it was running so I don't have the exact timestamp/frame where it locked up.   I can do it again if this would be helpful.
>Please try 
>ffmpeg -i 1504_20211225153600.ts  -vcodec libx264 -crf 24 -tune film -acodec copy 1504_20211225153600.libx264.ts
>and let me know if it completes.
>Since mine locks up, does this mean there is a bug in my AMD CPU?
>I notice this in my output:
>[libx264 @ 0x5567615eaac0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX XOP FMA3 BMI1

So running the ffmpeg command causes the PC to lock up?  That should
not be able to lock up the PC, as it does not involve the use of
drivers or anything else that runs on ring 0 of the CPU, so even if
something went badly wrong with the ffmpeg process, it would be easy
to just kill it from the command line and everything else would just
keep working.

So if ffmpeg is locking up the PC, the obvious cause of that is
overheating.  When you run ffmpeg with a "-vcodec libx264" option,
that is causing it to convert the existing video stream to H.264,
which is a very CPU intensive operation.  If the CPU is having
problems with its cooling, that much CPU use is likely to trigger
either an emergency shutdown of the CPU, or a lockup.  When did you
last clean the CPU heatsink and fan to remove all the dust?

It is also possible in a PC that old that the heatsink compound
between the CPU and the heatsink has dried out and is no longer
transferring the heat to the heatsink properly.  That is a bit more
difficult to fix, as you would have to get some new heatsink compound,
remove the heatsink from the CPU, clean off the old heatsink compound,
apply the new (making sure it was spread around properly and not too
thin or thick) and then reinstall the heatsink and fan.  There is
likely video out there to show you exactly how.

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