[mythtv-users] v30 and DVB-T2 part-time channels - recordings without audio/video hanging mythfrontend

[Mark Cooke]

Hi All,

I finally managed to get my system updated from v28 (Ubuntu 16.04) to 
v30 (Ubuntu 18.04).

I am using a self-compiled front end on OSX 10.13 (quite an involved 
process but thanks to everyone posting top tips to the forum and list).

* Started with 
https://github.com/warpme/mythv-osx-build-script/blob/master/osx-packager-qtsdk.pl
* Updated to freetype 2.10.0
* Updated to QT 5.11.3
* Used MacPorts for python and freetype issue
* Used the SDK workaround for Quicktime framework missing from 
https://github.com/warpme/mythv-osx-build-script



It was mostly plain sailing with using MythTV 30 itself, so thank you 
devs for the hard work!


I have come across one issue that appears to be due to the UK habit of 
having channels that broadcast 24x7 but only contain audio/video streams 
for some of the time.


The example I have most recently was from today.

BBC FOUR HD starts broadcasting at 7pm, and I had a recording setup for 
the broadcast starting at 7pm.  With a system-wide 'start recording 
early' configured, the TS file started to be saved from 6.50pm.


Trying to play this recording jams up the frontend with a black screen 
saying 'Please Wait'.  I can't escape, jump forward or backward or bring 
up the menu when this happens.

Eventually (5+ minutes later) it drops back to the Watch Recording 
screen with an error 'Video frame buffering failed too many times'.


Outside of MythFrontend, the TS file will play (eventually) in VLC, with 
the first video frame being ~ 650 MB into the file.


So Myth appears to hiccup with TS files without audio/video, and I don't 
know how to nicely fix this, other than avoid it happening by looking 
carefully at recording rules.


Anyone want this particular TS file to look further?  I have an 80MB 
chunk that covers the period just before the start of broadcast, and the 
700MB snip that Myth was struggling with.


mediainfo on the long lead in doesn't detect the video/audio stream but 
there is a menu stream present, so the recording isn't completely absent:

General
ID                                       : 45056 (0xB000)
Complete name                            : snip.ts
Format                                   : MPEG-TS
File size                                : 700 MiB

Menu
ID                                       : 1004 (0x3EC)
Menu ID                                  : 1 (0x1)
List                                     : 206 (0xCE) ()


On the short extract, it is short enough that mediainfo reaches the 
start of the audio/video:

General
ID                                       : 45056 (0xB000)
Complete name                            : snip2.ts
Format                                   : MPEG-TS
File size                                : 80.0 MiB
Duration                                 : 1 s 260 ms
Overall bit rate mode                    : Variable
Overall bit rate                         : 2 731 kb/s

Video
ID                                       : 201 (0xC9)
Menu ID                                  : 1 (0x1)
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High at L4
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 4 frames
Codec ID                                 : 27
Duration                                 : 680 ms
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 25.000 FPS
Standard                                 : Component
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

Audio
ID                                       : 202 (0xCA)
Menu ID                                  : 1 (0x1)
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Muxing mode                              : LATM
Codec ID                                 : 17-2
Duration                                 : 1 s 260 ms
Bit rate mode                            : Variable
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 46.875 FPS (1024 SPF)
Compression mode                         : Lossy
Language                                 : English

Text
ID                                       : 203 (0xCB)
Menu ID                                  : 1 (0x1)
Format                                   : DVB Subtitle
Codec ID                                 : 6
Language                                 : English

Menu
ID                                       : 1004 (0x3EC)
Menu ID                                  : 1 (0x1)
Duration                                 : 1 s 260 ms
List                                     : 206 (0xCE) () / 201 (0xC9) 
(AVC) / 202 (0xCA) (AAC, English) / 203 (0xCB) (DVB Subtitle, English)
Language                                 :  /  / English / English


Cheers,

Mark