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

Vincent Poore vincepoore at yahoo.com
Sat Dec 25 19:31:32 UTC 2021

 I tried converting the codecs using the command you supplied ffmpeg -i temp.ts -vcodec libx264 -crf 24 -tune film -acodec copy (mythrecname).ts

Surprise!   That locked up my machine after it had gotten about 5 minutes in.
ffprobe reported these streams in that file.Input #0, mpegts, from '1504_20211224010000.original.ts':  Duration: 00:34:27.45, start: 22646.908422, bitrate: 7758 kb/s  Program 1     Stream #0:0[0x760]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv, top first), 1920x1080 [SAR 1:1 DAR 16:9], Closed Captions, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc    Stream #0:1[0x761](eng): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, 5.1(side), fltp, 384 kb/s    Stream #0:2[0x762](spa): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 128 kb/s

    On Friday, December 24, 2021, 07:19:12 PM MST, glen <glenb at glenb.net> wrote:  
 On Sat, 2021-12-25 at 01:25 +0000, Vincent Poore via mythtv-users wrote:
I've been living with and frustrated by a problem with recordings from my local CBS broadcast channel.
It all started when my local station added a new digital sub-channel.   I know this because my problem started on March 1st and a call to the station engineer confirmed changes were made to the broadcast signal early that Sunday morning. He says, "Everything in this encoding scheme is industry standard, so I wouldn’t expect there to be any problem decoding it with commercial equipment."  I'm not technical enough to determine what has changed that would give mythtv so much trouble.  Here are the symptoms:
Prior to the change, I used VDPAU High Quality Video Playback Profile.   After the change, this profile on the bad channel will eventually cause my machine to lock up.  It starts with some serious macro blocking and then eventually freezes the display and I have to use power reset to recover my machine.   I discovered I am able to view the programs using Open GL High Quality.   I'm not happy about the higher CPU, but at least I can watch my programs.   However, two other bad symptoms manifest.
After the change, the timing information of the recordings is off.   A 60 minute recording, when paused will report as 75 minutes.
I suspect this is related to the third symptom which is that skip forward or back doesn't work properly.  The first skip forward will actually jump backward some random offset (usually 3 or 4 minutes) and then progress forward from there with repeated commands.   A skip backward does the same thing (first skip offset backwards 3 to 4 minutes).
Note: I don't run any transcoding jobs on my recordings.   I've upgraded to Ubuntu 20.04.3 with latest mythtv patches (31.0+fixes.202111081900.25f1bb1d12~ubuntu20.04.1).
Any suggestions?_______________________________________________
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i would check a few things to experiment. i assume the capture (.ts file in myth) is mpeg2 and ac3 audio .. right ?
first on a completed recording see if just changing the container does anything. first move the finished file to a temp file: mv (mythrecname).ts temp.ts  then run: ffmpeg -i temp.ts -vcodec copy -acodec copy (mythrecname).ts after that check in the frontend and see if you have the same issues.  
if you still have those issues then consider just running a transcode job with ffmpeg when the recording completes and transcode the video to libx264..you could do it as a user job script and just filter for the offending channel. but first test it with
run: mv (mythrecname).ts temp.ts then run: ffmpeg -i temp.ts vcodec libx264 -crf 24 -tune film -acodec copy (mythrecname).ts
you would probably want to customize the ffmpeg libx264 options for deinterlace if you need etc... but it should play ok in the frontend.  
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