Opened 15 years ago

Closed 15 years ago

#2311 closed defect (fixed)

DVB offline mheg Banner page remains onscreen when recording starts

Reported by: anonymous Owned by: Stuart Auchterlonie
Priority: minor Milestone: 0.21
Component: mythtv Version: head
Severity: medium Keywords: mheg
Cc: Ticket locked: no


For recordings starting a few mins before a channel comes online the Banner page is correctly displayed. Unfortunately it does not dissapear when the programme starts (although it is partly transparent). Quick fix is to press edit recording and delete the first few mins - then all is OK.

Attachments (1)

mhegstartpatch.txt (10.5 KB) - added by dm@… 15 years ago.

Download all attachments as: .zip

Change History (8)

comment:1 Changed 15 years ago by Isaac Richards

Owner: changed from Isaac Richards to Stuart Auchterlonie

comment:2 Changed 15 years ago by Stuart Auchterlonie

Keywords: mheg added
Milestone: unknown0.21
Status: newassigned

Confirmed the problem exists. It's possible the mheg engine isn't responding correctly to requests to shutdown the mheg output.

comment:3 Changed 15 years ago by dm@…

The Data Broadcast ID descriptor in the PMT contains a Network boot info sub-descriptor. If the version number in this changes and the action field is "boot" the MHEG application is supposed to be rebooted. I made a recording when BBC THREE started at 7pm and this is what happens. I would assume that other broadcasters do the same.

Parsing the sub-descriptor in mpegts.c isn't too difficult but passing the information up to the MHEG application isn't so obvious, probably requiring additional fields in the AVStream structure. It would be better if there was a standard way of passing the descriptor information up to avformatdecoder rather than having ad hoc solutions. I'll work on a patch anyway.

comment:4 Changed 15 years ago by anonymous

FYI We place a copy of the last PMT section seen in AVFormatContext::cur_pmt_sect, you can see this being used in avformatdecoder.

comment:5 Changed 15 years ago by Stuart Auchterlonie

The PMT would have to change at these program boundaries, so why not just reset the mheg engine on a PMT change?

Changed 15 years ago by dm@…

Attachment: mhegstartpatch.txt added

comment:6 Changed 15 years ago by dm@…

This patch fixes the problem for my recording of BBC THREE start up. I would expect that it would also work for the other BBC channels such as BBC FOUR.

This patch also contains a work-around for #2576, an apparently similar problem when ITV4 starts up, but which arises from a completely different situation. In this case the off-air MHEG application looks for a change in a file in the DSMCC carousel when the channel comes on-air. The broadcaster sends an updated file but does not update the version number for the module containing it in the data carousel. The DSMCC code therefore does not reload the module and the file doesn't change. I've worked around this by flushing a module from the cache if the size of the module given in the DII table changes as well as if the version changes.


comment:7 Changed 15 years ago by Stuart Auchterlonie

Resolution: fixed
Status: assignedclosed

(In [11598]) Closes #2311, Refs #2576. Adds support for restarting the MHEG engine when requested by the broadcaster. This is used in the UK when channels transition from off air to on air.

Thanks to David Matthews for the patch.

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