[mythtv-commits] Ticket #3465: BBC HD on DVB-S dropped video frames. [ Not in mplayer/vnc ]

MythTV mythtv at cvs.mythtv.org
Wed May 16 09:42:00 UTC 2007


#3465: BBC HD on DVB-S dropped video frames. [ Not in mplayer/vnc ]
-----------------------+----------------------------------------------------
 Reporter:  anonymous  |       Owner:  ijr    
     Type:  defect     |      Status:  new    
 Priority:  minor      |   Milestone:  unknown
Component:  mythtv     |     Version:  unknown
 Severity:  medium     |  
-----------------------+----------------------------------------------------
 I am seeing dropped frames in mythtv while playing back BBC HD-TV. this is
 an h.264 MBAFF stream, so has fairly heavy cpu requirements. I can play
 these streams back cleanly on the same machine under windows, and using
 vlc/mplayer. Looking at mythfrontend -v playback, frames are being dropped
 because the audio is 3 frames out of step with the video. Increasing the
 tolerance on this with a quick hack does not solve the problem. I am run
 tests on current SVN, using both FFMPEG (h264) and with the coreavc patch
 to give me more headroom on the cpu.

 Originally posted to mythtv-users.
 {{{

 PC is core2duo e4300 [overclocked], graphics card nvidia 7300Ls. Cpu
 load is recorded as {cpu core0:core1}

 Windows2000:
 2.7GHz : VLC: ffmpeg: no skiploopfilter: BBC-HD MBAFF h.264: CPU 60%:20%
 smooth.
 2.7GHz : VLC: ffmpeg: skiploopfilter: BBC-HD MBAFF h.264: CPU 40%:10%
 smooth.
 2.7GHz : MplayerClassic: coreavc: no skiploopfilter: BBC-HD MBAFF h.264:
 CPU 60%:30% smooth.
 2.7GHz : MplayerClassic: coreavc: skiploopfilter: BBC-HD MBAFF h.264: CPU
 40%:20% smooth.

 Ubuntu 7.04. .

 2.7GHz : VLC: ffmpeg: no skiploopfilter: BBC-HD MBAFF h.264: CPU 100%:20%
 and dropped frames.
 2.7GHz : VLC: ffmpeg: skiploopfilter: BBC-HD MBAFF h.264: CPUs 90%:20%
 smooth.
 2.7GHz : Mythtv: ffmpeg: skiploopfilter: BBC-HD MBAFF h.264: CPU 90%:20%
 and dropped frames.
 2.7GHz : Mythtv: coreavc: skiploopfilter: BBC-HD MBAFF h.264: CPU 40%:40%
 and dropped frames.

 So it looks as if I can reduce the quality of the ffmpeg decoding by
 using skiploopfilter to not max out the CPU, or use a non-free coreavc
 codec. However Mythtv is still doing somthing odd with the Sync between
 Audio and Video which is leading to it detecting the audio falling out
 of sync with the video, and then dropping video frames to resync.

 }}}

-- 
Ticket URL: <http://svn.mythtv.org/trac/ticket/3465>
MythTV <http://svn.mythtv.org/trac>
MythTV


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