[mythtv-commits] Ticket #10007: Video lags audio (sync) by ~400ms on hd pvr 1212 h264 recordings (only) after firmware update.

MythTV noreply at mythtv.org
Thu Aug 25 14:53:46 UTC 2011


#10007: Video lags audio (sync) by ~400ms on hd pvr 1212 h264 recordings (only)
after firmware update.
-----------------------------------------+----------------------------
     Reporter:  gdelx001@…               |      Owner:  markk
         Type:  Bug Report - General     |     Status:  new
     Priority:  minor                    |  Milestone:  unknown
    Component:  MythTV - Video Playback  |    Version:  0.24.1
     Severity:  medium                   |   Keywords:  video lag sync
Ticket locked:  0                        |
-----------------------------------------+----------------------------
 My Hauppauge HD PVR 1212's output has played flawlessly on the current
 version of mythtv for some time, but that stopped immediately once I had
 to update the firmware on the device to gain stability on initiating
 recording with the stb to which it is attached (it either worked or didn't
 - there wasn't a problem with a successful recording, before now).

 Now I am having a problem with MythTV 0.24.1-2 (rpmfusion distribution for
 Fedora 14) player audio sync on streams made by the Hauppauge HD PVR 1212.
 Different playback hardware has the same problem.  Different recording
 hardware (a Hauppauge composite video  recording card) which produces a
 different output format (MPEG) does not exhibit the problem.  The audio
 leads the video by (typically) 400ms so you noticeably and annoyingly hear
 action before you see it.  This can be adjusted on each playback by hand
 using the audio sync menu item and the delay is stable throughout the
 recording.  But given the impermanence of the setting and applicability
 specifically to that device's recordings this isn't an acceptable long
 term solution.

 I have confirmed that this sync issue doesn't occur playing the same exact
 streams back in VLC.  Nor does going to software playback from VDPAU in
 MythTV appear to have any fundamental effect.  There aren't always
 messages in the xsession log indicating the problem, although sometimes
 there are indications from the frontend that some expected structures are
 missing from the stream ("non-existing PPS referenced" or "non-existing
 SPS 4 referenced in buffering period" or "no frame!" or
 "decode_slice_header error").  Since these don't always occur and the mis-
 sync of audio always occurs (with h264) I'm not focusing on them.

 This didn't happen before a recent firmware update on the HD PVR taking it
 from version 0xf to 0x17 (May 2009->July 2011 release date), leading me to
 _speculate_ that some assumptions made by MythTV about h264 streams are no
 longer met, that Hauppauge tightened or expanded their adherence to spec,
 which VLC can tolerate and MythTV can't.

 If it's thought to be the most fruitful course, I'm willing to spellunk
 with a hex editor or other viewer in the files (examples before and after
 the firmware change) and diff'ing to help identify the problem if I'm
 given some direction about tools and where to focus.  Alternatively if
 snippets of the large recording files are desired, instructions on how to
 do best to extract would be helpful.

-- 
Ticket URL: <http://code.mythtv.org/trac/ticket/10007>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center


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