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

MythTV mythtv at cvs.mythtv.org
Tue Jun 24 15:27:34 UTC 2008

#5462: Displayed program length is 1.25X of actual length with pvrusb2
 Reporter:  dan.bodoh at gmail.com  |        Owner:  danielk 
     Type:  defect               |       Status:  assigned
 Priority:  minor                |    Milestone:  unknown 
Component:  mythtv               |      Version:  unknown 
 Severity:  medium               |   Resolution:          
  Mlocked:  0                    |  

Comment(by dan.bodoh at gmail.com):

 Not sure I understand the question, probably because I know very little
 about the pvrusb2 driver and even less about mythtv code.  I don't have a
 patch, but I've done a little research and some code inspection of the
 linux driver code.

 The Hauppauge PVR-USB2 is an MPEG2 encoding device (really, it's just a
 PVR-350 over the USB bus).  Mythtv talks to it via the pvrusb2 module,
 which is similar to the old ivtv module since the devices share hardware.
 In fact, I believe that mythtv doesn't really know that it's talking to a
 PVR-USB2; the module interface is no different that ivtv.

 So I don't understand what you mean that "we should be writing keyframes
 correctly".  It would seem to me that the keyframes are already part of
 the MPEG2 stream coming in, and mythtv really doesn't do much but save
 that stream to disk.

 There's a technical discussion about the use of gop size of 12, instead of
 15, for NTSC by the pvrusb2 module in the thread following
 http://www.isely.net/pipermail/pvrusb2/2008-June/001832.html.  It appears
 that pvrusb2 or a lower module *should* set the gop size to 15 for NTSC,
 but they don't.

 However, if gop size of 12 is legal (but undesirable?) for NTSC, it
 appears that there is a bug in the mythtv playback (not recording).
 Playing gop=12 NTSC seems to have 2 effects in mythtv playback: (1) the
 OSD display of program length is 1.25X of the actual length, probably
 because mythtv assumes a gop of 15, which is 1.25X of the actual gop of
 12. (2) marking a position, and then jumping to that position when re-
 entering playback actually jumps to an earlier position in the recording.

Ticket URL: <http://svn.mythtv.org/trac/ticket/5462#comment:4>
MythTV <http://www.mythtv.org/>

More information about the mythtv-commits mailing list