[mythtv-users] Segfault on starting playback

[Jim Stichnoth]

On Sun, Aug 26, 2012 at 1:12 PM, Stephen Robertson
<stephengrobertson at gmail.com> wrote:
> On Sunday, August 26, 2012, Douglas Mackay wrote:
>>
>> On 26 August 2012 10:53, Douglas Mackay <douglas.mackay at gmail.com> wrote:
>> > On 26 August 2012 10:01, Douglas Mackay <douglas.mackay at gmail.com>
>> > wrote:
>> >> Not sure if this helps but I'm also experiencing a similar issue.
>> >>
>> >> I've got two crash reports on Launchpad (one from a remote frontend
>> >> and the other from the backend)
>> >>
>> >> https://bugs.launchpad.net/mythbuntu/+bug/1041788
>> >> https://bugs.launchpad.net/mythbuntu/+bug/1041797
>> >
>> > If I manually run mythpreviewgen on the recording then is crashes
>> > about 50% of the time. This recording was from Freeview (UK).
>>
>> I've done further testing and from what I can see it just affects BBC
>> channels (SD, HD on both UK Freeview and UK Freesat). These channels
>> have digital teletext services.
>>
>> Sample (6MB) - http://www.filedropper.com/100120120826105500
>> ______________________________________________
>
>
> I hadn't noticed this as the vast majority of my recordings are BBC but this
> seems to be the case for me too.

This is a request for help from the people who are experiencing these
crashes.  I am trying to investigate this problem (there are at least
3 tickets that seem to be reporting this same thing), but it is
challenging because I can't reproduce the crash on my system.
However, there are indications from valgrind that uninitialized memory
may be involved.  Specifically, if I use valgrind in this way:

valgrind --leak-check=full --error-limit=no --show-reachable=yes
/usr/mythtrunk/bin/mythavtest -v general,playback,libav --loglevel
debug myth://Videos@192.168.0.205:6543/broken.mpg

Part of the valgrind output looks like this:

...
2012-08-29 13:17:33.668634 D  mpegts_add_stream: stream #11, has id
0x1c25 and codec DSMCC_B, type Data at 0x134ef380
==15679== Conditional jump or move depends on uninitialised value(s)
==15679==    at 0x411497E: mpegts_push_section (mpegts-mythtv.c:674)
==15679==    by 0x4114B6E: write_section_data (mpegts-mythtv.c:401)
==15679==    by 0x41173CD: handle_packet (mpegts-mythtv.c:2527)
==15679==    by 0x7021BC63: ???
==15679==
==15679== Conditional jump or move depends on uninitialised value(s)
==15679==    at 0x4114985: mpegts_push_section (mpegts-mythtv.c:684)
==15679==    by 0x4114B6E: write_section_data (mpegts-mythtv.c:401)
==15679==    by 0x41173CD: handle_packet (mpegts-mythtv.c:2527)
==15679==    by 0x7021BC63: ???
==15679==
==15679== Conditional jump or move depends on uninitialised value(s)
==15679==    at 0x411497E: mpegts_push_section (mpegts-mythtv.c:674)
==15679==    by 0x4114B6E: write_section_data (mpegts-mythtv.c:401)
==15679==    by 0x41173CD: handle_packet (mpegts-mythtv.c:2527)
==15679==    by 0x8792: ???
==15679==
==15679== Conditional jump or move depends on uninitialised value(s)
==15679==    at 0x4114985: mpegts_push_section (mpegts-mythtv.c:684)
==15679==    by 0x4114B6E: write_section_data (mpegts-mythtv.c:401)
==15679==    by 0x41173CD: handle_packet (mpegts-mythtv.c:2527)
==15679==    by 0x8792: ???
==15679==
==15679== Conditional jump or move depends on uninitialised value(s)
==15679==    at 0x411497E: mpegts_push_section (mpegts-mythtv.c:674)
==15679==    by 0x4114B6E: write_section_data (mpegts-mythtv.c:401)
==15679==    by 0x41173CD: handle_packet (mpegts-mythtv.c:2527)
==15679==    by 0x6FDC685: ??? (in /usr/lib/libQtGui.so.4.6.2)
==15679==
==15679== Conditional jump or move depends on uninitialised value(s)
==15679==    at 0x4114985: mpegts_push_section (mpegts-mythtv.c:684)
==15679==    by 0x4114B6E: write_section_data (mpegts-mythtv.c:401)
==15679==    by 0x41173CD: handle_packet (mpegts-mythtv.c:2527)
==15679==    by 0x6FDC685: ??? (in /usr/lib/libQtGui.so.4.6.2)
==15679==
==15679== Conditional jump or move depends on uninitialised value(s)
==15679==    at 0x411497E: mpegts_push_section (mpegts-mythtv.c:674)
==15679==    by 0x4114B6E: write_section_data (mpegts-mythtv.c:401)
==15679==    by 0x41173CD: handle_packet (mpegts-mythtv.c:2527)
==15679==    by 0x1F03EB59: ???
==15679==
==15679== Conditional jump or move depends on uninitialised value(s)
==15679==    at 0x4114985: mpegts_push_section (mpegts-mythtv.c:684)
==15679==    by 0x4114B6E: write_section_data (mpegts-mythtv.c:401)
==15679==    by 0x41173CD: handle_packet (mpegts-mythtv.c:2527)
==15679==    by 0x1F03EB59: ???
==15679==
2012-08-29 13:17:35.174329 I  AFD: Stream #0, has id 0x12d codec id
MPEG2VIDEO, type Video, bitrate 15000000 at 0x12c8d720
...

This valgrind output related to mpegts-mythtv.c lines 674 and 684
seems to correlate to the stack traces in the crash reports, and
appears just after the last bit of log output before the crashes.

So I'd like to ask anyone who can reproduce this crash, if they can
run valgrind in the same way, and see where the crash happens with
respect to the valgrind output.

Jim