[mythtv-commits] Ticket #5462: Displayed program length is 1.25X of actual length with pvrusb2

MythTV mythtv at cvs.mythtv.org
Sun Jun 22 17:09:37 UTC 2008

#5462: Displayed program length is 1.25X of actual length with pvrusb2
 Reporter:  dan.bodoh at gmail.com  |       Owner:  ijr    
     Type:  defect               |      Status:  new    
 Priority:  minor                |   Milestone:  unknown
Component:  mythtv               |     Version:  unknown
 Severity:  medium               |     Mlocked:  0      
 When playing back recordings, the program length displayed with the "i"
 keystroke is too long.  For a 1 hour program, it says 1:15.

 Hardware: PVR-USB2 encoder, NTSC input, displayed on S-Video out port of
 intel gm965 using 'intel' driver in Ubuntu Hardy.

 Workaround is to set the video_gop_size for the PVR-USB2 to 15.  The
 default is 12.  (echo 15 > /sys/class/pvrusb2/<PUT YOUR SERIAL NUMBER

 In other words, it appears that the mythtv decoder doesn't properly
 display the recorded time length for NTSC signals encoded in MPEG2 with a
 gop size of 12. [12 * 1.25 = 15, which mythtv seems to assume] There's
 also a jerkiness during motion that might be solved by this workaround,
 but I need to observe more recordings to make sure.

 I don't know much about MPEG-2, so I don't know if a gop size of 12 is
 legal for NTSC.  If not, this is probably a pvrusb2 or cx2341x driver bug.
 From inspection of the linux 2.26.25 source, it appears that cx2341 module
 sets the default of frames per gop of 12, and pvrusb2 does not change it
 (although at least older versions of IVTV changed it 15 for my old

Ticket URL: <http://svn.mythtv.org/trac/ticket/5462>
MythTV <http://www.mythtv.org/>

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