[mythtv-commits] Ticket #12054: Local commercials confuse CEA-608 caption decoding

MythTV noreply at mythtv.org
Tue Jul 22 04:56:42 UTC 2014


#12054: Local commercials confuse CEA-608 caption decoding
-----------------------------------+--------------------------------
 Reporter:  faginbagin <mythtv@…>  |          Owner:  stichnot
     Type:  Bug Report - General   |         Status:  infoneeded_new
 Priority:  minor                  |      Milestone:  0.27.4
Component:  MythTV - Captions      |        Version:  0.27-fixes
 Severity:  medium                 |     Resolution:
 Keywords:                         |  Ticket locked:  0
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Comment (by faginbagin <mythtv@…>):

 I get the same result as you when I run mythccextractor. I am using mythtv
 packages from ubuntu. Here's the output from mythfrontend --version:
 {{{
 Please attach all output as a file in bug reports.
 MythTV Version : v0.27.3-6-gfba8e80
 MythTV Branch : fixes/0.27
 Network Protocol : 77
 Library API : 0.27.20140702-1
 QT Version : 4.8.4
 Options compiled in:
  linux profile use_hidesyms using_alsa using_oss using_pulse
 using_pulseoutput using_backend using_bindings_perl using_bindings_python
 using_bindings_php using_crystalhd using_dvb using_firewire using_frontend
 using_hdhomerun using_ceton using_hdpvr using_ivtv using_joystick_menu
 using_libcec using_libcrypto using_libdns_sd using_libfftw3 using_libxml2
 using_lirc using_mheg using_opengl using_opengl_video using_qtwebkit
 using_qtscript using_qtdbus using_sdl using_taglib using_v4l2 using_x11
 using_xrandr using_xv using_profiletype using_bindings_perl
 using_bindings_python using_bindings_php using_mythtranscode using_opengl
 using_vaapi using_vdpau using_ffmpeg_threads using_mheg using_libass
 using_libxml2
 }}}

 However, if I strip off the leading commercial from the clip using:
 {{{
 dd if=cc608-disappears.mpg of=temp.mpg bs=7828320 skip=1
 }}}
 Then, mythccextractor can extract the captions from temp.mpg. And the log
 output is roughly double what it was for the original cc608-disappears.mpg

 Could it be that the commercial has ATSC caption data, but the actual
 program doesn't and that's what's confusing myth? Remember, I'm 99% sure
 the commercial was inserted by my local cable provider, WOW (aka Wide Open
 West), and was not part of the original stream provided by Comedy Central.
 Seeking doesn't fix things, only bookmarking, stopping and restarting
 playback from the bookmark gets the captions back. We have to do this with
 content recorded from other basic cable channels, too. And always after a
 commercial, but not after every commercial.

 FWIW, we also see a possibly related problem on some PBSHD shows from the
 BBC where we turn on CCs and don't see any captions unless we use the menu
 to explicitly switch from ATSC to VBI. One in particular is "Death in
 Paradise" on Thursday nights at 9pm EDT. It's a crime drama with a sense
 of humor. If you're in the USA it would be interesting to know if your
 broadcast of this show has the same problem.

--
Ticket URL: <https://code.mythtv.org/trac/ticket/12054#comment:5>
MythTV <http://www.mythtv.org>
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