[mythtv] Too much EIT activity causing defective recordings

Wed Aug 1 12:52:06 UTC 2018

On 01/08/18 12:49, Michael T. Dean wrote:
> On 07/31/2018 06:51 PM, John Pilkington wrote:
>> Hi;  I'm running Master under SL7, recording UK SD DVB-T material via 
>> one PCI single-tuner device and one twin-tuner usb dongle.
>>
>> Bus 001 Device 002: ID 1b80:e409 Afatech IT9137FN Dual DVB-T [KWorld 
>> UB499-2T]
>>
>> Around 9 July my Project-X-based mythDVBcut logs started reporting 
>> multiple AV sync corrections of up to a second in recordings from the 
>> usb tuners.  The change occurred after I rescanned my transports 
>> following the Wimbledon special tennis coverage;  I'm fairly sure I 
>> made other 'minor' changes in the multirec and EIT configs too.
>>
>> Today I realised that the defects were often around 5 minutes apart, 
>> and EIT scanning seemed a possible culprit.  I have now unchecked the 
>> boxes for usb open-on-demand and active-EIT-scan, and it looks as if 
>> the recording defects have largely gone.
>>
>> In the past I probably haven't taken as much notice of the EIT 
>> settings as I should have done, but the recent defects were much worse 
>> than I had seen before and I think some of the recent code changes 
>> must have been implicated.
>>
>> John P
>>
>> Below is a Project-X log resync section from an affected recording. 
>> This should be just a few lines, with no resync required.
>>
>> {{{
>>
>> Input File 0:  '/mnt/dat2/RSG3/1004_20180723195800.ts.old' 
>> (1,149,983,780 bytes)
>> -> Filetype is TS (generic PES Container)
>>
>> <demux log snipped>
>>
>> ++> Mpg Audio: PID 0x044E / PesID 0xC0 / SubID 0x00 :
>> -> check CRC of AC-3 / MPEG-Audio L1,2
>> -> remove CRC in MPEG-Audio L1,2
>> -> add frames
>> -> Audio PTS: first packet 08:48:35.071, last packet 09:48:52.207
>> -> Video PTS: start 1.GOP 08:48:41.439, end last GOP 09:48:41.999
>> -> adjusting audio at video-timeline
>> -> src_audio: MPEG-1, Layer2, 48000Hz, stereo, 192kbps, noCRC @ 
>> 00:00:00.000
>> !> 5 frame(s) (120ms) inserted @ 00:02:28.608
>> !> missing syncword @  6527233, @ 00:04:08.064
>> !> found syncword @ 6528384
>> !> 22 frame(s) (528ms) inserted @ 00:04:08.064
>> !> missing syncword @  6528961, @ 00:04:08.592
>> !> found syncword @ 6529352
>> !> missing syncword @  14213193, @ 00:09:27.840
>> !> found syncword @ 14213560
>> !> missing syncword @  14214137, @ 00:09:27.864
>> !> found syncword @ 14214344
>> !> 4 frame(s) (96ms) inserted @ 00:09:27.864
>> !> missing syncword @  29606793, @ 00:16:02.448
>> !> found syncword @ 29607000
>> !> 1 frame(s) (24ms) inserted @ 00:16:02.448
>> !> 19 frame(s) (456ms) inserted @ 00:21:21.144
>> !> missing syncword @  45001753, @ 00:26:40.656
>> !> found syncword @ 45001960
>> !> 23 frame(s) (552ms) inserted @ 00:26:40.680
>> !> missing syncword @  52701353, @ 00:27:54.144
>> !> found syncword @ 52701536
>> !> missing syncword @  52702689, @ 00:27:54.192
>> !> found syncword @ 52703080
>> !> 20 frame(s) (480ms) inserted @ 00:27:54.192
>> !> missing syncword @  60403625, @ 00:33:14.592
>> !> found syncword @ 60404248
>> !> 17 frame(s) (408ms) inserted @ 00:33:14.616
>> !> missing syncword @  68103065, @ 00:38:34.344
>> !> found syncword @ 68103712
>> !> 17 frame(s) (408ms) inserted @ 00:38:34.344
>> !> missing syncword @  68120993, @ 00:38:34.752
>> !> found syncword @ 68121960
>> !> 2 frame(s) (48ms) inserted @ 00:38:34.752
>> !> missing syncword @  75797161, @ 00:39:47.760
>> !> found syncword @ 75797944
>> !> missing syncword @  83496185, @ 00:45:07.344
>> !> found syncword @ 83496968
>> !> 21 frame(s) (504ms) inserted @ 00:45:07.416
>> !> missing syncword @  83504457, @ 00:45:07.920
>> !> found syncword @ 83505080
>> !> missing syncword @  83566137, @ 00:45:09.816
>> !> found syncword @ 83566920
>> !> 2 frame(s) (48ms) inserted @ 00:45:09.816
>> !> 2 frame(s) (48ms) inserted @ 00:45:09.960
>> audio frames: wri-pre-skip-ins-add 117813-0-0-155-0 @ 00:47:07.512 
>> done...
>> ---> new File: '/home/john/MythTmp/tempcut19417.mp2'
>>
>> summary of created media files:
>> .Video (m2v):    70688 Frames    00:47:07.520 
>> '/home/john/MythTmp/tempcut19417.m2v'
>> Audio 00 (mp2):    117813 Frames    00:47:07.512    0-0-155-0 
>> '/home/john/MythTmp/tempcut19417.mp2'
>> => 775,195,585 bytes written...
>> -> we have 139 warnings/errors.
>>
>> }}}
> 
> Could this be due to I/O activity? Have you done an optimize on your 
> database, recently?  If not, it may just be that MySQL is taking too 
> much time with I/O when MythTV tries to write your listings data and it 
> causes problems with MythTV's writing recording data.  Do you have any 
> warnings or errors in your MythTV backend logs?
> 
> Mike

Hi Mike:  I run optimize every few days, so I don't think that's it. 
But I usually arranged the schedule to record from the usb tuners only 
when the PCI device was already recording, often from several channels, 
so usually the system would be fairly busy.  Database sql.gz backups are 
now 125 MiB and autodelete of old recordings is getting invoked.  40 GB 
free, 2% of 2.3 GiB reported: 3 partitions on 2 disks.

I haven't seen any obvious signs of distress on the terminal window in 
which I run the backend, and at present I would prefer to let things 
roll for a bit rather than going back to do more investigations.

Cheers,

John