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

John Pilkington johnpilk222 at gmail.com
Sat Dec 25 20:19:44 UTC 2021

On 25/12/2021 19:31, Vincent Poore via mythtv-users wrote:
> 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?
>> _______________________________________________
>> mythtv-users mailing list
>> mythtv-users at mythtv.org <mailto:mythtv-users at mythtv.org>
>> http://lists.mythtv.org/mailman/listinfo/mythtv-users 
>> <http://email.mg.glenb.net/c/eJwtjcsOgyAURL9GdyWIXNEFi276H5cLKAkPg9TEv69tmpnVOZOM1eTRguyDnpSVhiQZYRZLdjFKCFQG5js0-GkQRFyNnBEmFzvJ1-iyYdm1ftMGOHlvAUAoOUrLAecB50V4A4DC9lFvre3d-OzE624MRztYutrWTlbqeqOEISbMfxmyL1_4Wzzeh6tHX_UZMrm9lOru_wu3UhiV9AEsoj9v>
>> http://wiki.mythtv.org/Mailing_List_etiquette 
>> <http://email.mg.glenb.net/c/eJwNjTESgyAQAF-jJXOCiBQUaVIlb3DgOIWJijEXM_4-zm61zUaHo4-6rbPrTGwDthhksBGjDUZKb4LuL7AZu0YiglEg0C80Vy1MM61BrMR1ckoZHS1E7IC0NAAWFKAk1ZMGHUM9u8S8VepWyfvlL7-yWE5OfIiyT1d5-jzndRoe-cMDcX5_iZnq3R15RdpK2el6nj6VIrAsfxpTOsU>
>> MythTV Forums: https://forum.mythtv.org 
>> <http://email.mg.glenb.net/c/eJwNzDsOwyAQANHTmBKZ3wIFRZrcAxYwlow3IsSSbx9rXj05YI3ZaLYHsFkn1Jhk8hmzT1bKaJNxTygqCIm4WrVyjL0ci163o5yJn2WyFpwpWoD31SldAYyuaCEDCid9xajYEdqcn--iXot8PyqNX-f9nm1enMbGRrj2E8uHaJRnfsdGxJH6H1PbMnk>
> 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.

Plays fine for me with software decoding on a 2.8 GHz core2duo machine. 
But shock horror it's mpeg2video 1920x1080i @ 29.97 fps and the cpu load 
is close to 2 x 100%


John P

More information about the mythtv-users mailing list