[mythtv-users] The dreaded pre-buffering pause

Fri Apr 2 01:10:25 UTC 2010

 I'm trying to track down why my Atom 330 system keeps pausing with 
pre-buffering pauses when playing h.264 video.  It works just fine with 
lavc encoded video.

First of all, I'm running latest 0.23:

Please include all output in bug reports.
MythTV Version   : 23892
MythTV Branch    : branches/release-0-23-fixes
Network Protocol : 56
Library API      : 0.23.20100314-1
QT Version       : 4.5.0
Options compiled in:
 linux release using_oss using_alsa using_backend using_dvb 
using_frontend using_hdhomerun using_hdpvr using_iptv using_ivtv 
using_joystick_menu using_lirc using_mheg using_opengl_video 
using_opengl_vsync using_qtdbus using_qtwebkit using_v4l using_x11 
using_xrandr using_xv using_xvmc using_xvmc_vld using_bindings_perl 
using_bindings_python using_opengl using_ffmpeg_threads using_live 
using_mheg

Here's the output from mythfrontend.  I've highlighted the two lines 
that I think may be a source of the problem.  I'd appreciate any help on 
this.  The system runs fine, mythfrontend uses 55% CPU (which is 
consistent with the Atom 330's 2+2 CPU core structure - dual core + 
hyperthreading) and overall the system shows as 83% idle when playing 
back material.

2010-04-01 17:40:49.960 Current MythTV Schema Version (DBSchemaVer): 1254
2010-04-01 17:40:51.601 Registering Internal as a media playback plugin.
2010-04-01 17:40:52.268 Current MythMusic Schema Version 
(MusicDBSchemaVer): 1017
2010-04-01 17:40:52.389 MonitorRegisterExtensions(0x40, 
mp3,mp2,ogg,oga,flac,wma,wav,ac3,oma,omg,atp,ra,dts,aac,m4a,aa3,tta,mka,aiff,swa,wv)
2010-04-01 17:40:52.487 Current MythVideo Schema Version 
(mythvideo.DBSchemaVer): 1032
2010-04-01 17:40:52.551 XMLParseBase: Loading window theme from 
/usr/local/share/mythtv/themes/Terra/menu-ui.xml
2010-04-01 17:40:52.909 Loading menu theme from 
/usr/local/share/mythtv/themes/defaultmenu//mainmenu.xml
2010-04-01 17:40:52.916 Found mainmenu.xml for theme 'Terra'
2010-04-01 17:40:52.987 MythContext: Connecting to backend server: 
127.0.0.1:6543 (try 1 of 1)
2010-04-01 17:40:53.009 Using protocol version 56
2010-04-01 17:56:04.928 Loading menu theme from 
/usr/local/share/mythtv/themes/defaultmenu//library.xml
2010-04-01 17:56:07.510 XMLParseBase: Loading window theme from 
/usr/local/share/mythtv/themes/Terra/video-ui.xml
2010-04-01 17:56:07.732 New DB connection, total: 2
2010-04-01 17:56:07.733 Connected to database 'mythconverg' at host: 
localhost
2010-04-01 17:56:10.948 XMLParseBase: Loading window theme from 
/usr/local/share/mythtv/themes/Terra/video-ui.xml
2010-04-01 17:56:13.441 TV: Attempting to change from None to WatchingVideo
2010-04-01 17:56:14.321 AFD: Opened codec 0x98b53c0, id(H264) type(Video)
2010-04-01 17:56:14.321 AFD: codec MP3 has 2 channels
2010-04-01 17:56:14.321 AFD: Opened codec 0x98b1fc0, id(MP3) type(Audio)
2010-04-01 17:56:15.258 Opening audio device 'default'. ch 2(2) sr 48000 
(reenc 0)
2010-04-01 17:56:15.276 Opening ALSA audio device 'default'.

+++++++++++++++++++++++++++++++++++++++++++++++++

2010-04-01 17:56:15.281 ALSA, Warning: mmap not available, attempting to 
fall back to slow writes.

+++++++++++++++++++++++++++++++++++++++++++++++++

2010-04-01 17:56:15.345 Mixer unable to find control PCM
2010-04-01 17:56:15.345 Mixer unable to find control PCM

****************************************************************************

2010-04-01 17:56:15.445 VideoOutputXv: Desired video renderer 
'xvmc-blit' not available.
            codec 'H.264' makes 'xv-blit,xshm,xlib,' available, using 
'xv-blit' instead.

****************************************************************************

2010-04-01 17:56:15.454 VideoOutputXv: XVideo Adaptor Name: 'Intel(R) 
Textured Video'
2010-04-01 17:56:15.544 OSD Theme Dimensions W: 640 H: 480
2010-04-01 17:56:15.948 TV: Changing from None to WatchingVideo
2010-04-01 17:56:15.951 Realtime priority would require SUID as root.
2010-04-01 17:56:15.955 New DB connection, total: 3
2010-04-01 17:56:15.957 Connected to database 'mythconverg' at host: 
localhost
2010-04-01 17:56:15.974 ScreenSaverX11Private: DPMS Deactivated 1
2010-04-01 17:56:15.986 Video timing method: DRM
2010-04-01 17:56:20.017 No DTS Seeking Hack!
2010-04-01 17:56:20.048 [h264 @ 0xb673d300]B picture before any 
references, skipping
2010-04-01 17:56:20.048 [h264 @ 0xb673d300]decode_slice_header error
2010-04-01 17:56:20.048 [h264 @ 0xb673d300]no frame!
2010-04-01 17:56:20.048 AFD Error: Unknown decoding error
2010-04-01 17:56:20.052 [h264 @ 0xb673d300]B picture before any 
references, skipping
2010-04-01 17:56:20.052 [h264 @ 0xb673d300]decode_slice_header error
2010-04-01 17:56:20.052 [h264 @ 0xb673d300]no frame!
2010-04-01 17:56:20.052 AFD Error: Unknown decoding error
2010-04-01 17:56:20.601 No DTS Seeking Hack!
2010-04-01 17:56:20.641 [h264 @ 0xb673d300]reference picture missing 
during reorder
2010-04-01 17:56:20.641 [h264 @ 0xb673d300]Missing reference picture
2010-04-01 17:56:21.335 No DTS Seeking Hack!
2010-04-01 17:56:21.378 [h264 @ 0xb673d300]B picture before any 
references, skipping
2010-04-01 17:56:21.378 [h264 @ 0xb673d300]decode_slice_header error
2010-04-01 17:56:21.378 [h264 @ 0xb673d300]no frame!
2010-04-01 17:56:21.378 AFD Error: Unknown decoding error
2010-04-01 17:56:21.380 [h264 @ 0xb673d300]B picture before any 
references, skipping
2010-04-01 17:56:21.381 [h264 @ 0xb673d300]decode_slice_header error
2010-04-01 17:56:21.381 [h264 @ 0xb673d300]no frame!
2010-04-01 17:56:21.381 AFD Error: Unknown decoding error
2010-04-01 17:56:21.884 No DTS Seeking Hack!
2010-04-01 17:56:21.892 [h264 @ 0xb673d300]B picture before any 
references, skipping
2010-04-01 17:56:21.892 [h264 @ 0xb673d300]decode_slice_header error
2010-04-01 17:56:21.893 [h264 @ 0xb673d300]no frame!
2010-04-01 17:56:21.893 AFD Error: Unknown decoding error
2010-04-01 17:56:22.468 No DTS Seeking Hack!
2010-04-01 17:56:22.515 [h264 @ 0xb673d300]reference picture missing 
during reorder
2010-04-01 17:56:22.515 [h264 @ 0xb673d300]Missing reference picture
2010-04-01 17:56:22.572 [h264 @ 0xb673d300]reference picture missing 
during reorder
2010-04-01 17:56:22.572 [h264 @ 0xb673d300]Missing reference picture
2010-04-01 17:56:22.611 [h264 @ 0xb673d300]reference picture missing 
during reorder
2010-04-01 17:56:22.611 [h264 @ 0xb673d300]Missing reference picture
2010-04-01 17:56:28.834 NVP(0): prebuffering pause
2010-04-01 17:56:31.570 NVP(0): prebuffering pause
2010-04-01 17:56:32.051 WriteAudio: buffer underrun
2010-04-01 17:56:38.208 NVP(0): prebuffering pause
2010-04-01 17:56:38.715 WriteAudio: buffer underrun

Here's the output of cupinfo for one of the cores:

processor    : 3
vendor_id    : GenuineIntel
cpu family    : 6
model        : 28
model name    : Intel(R) Atom(TM) CPU  330   @ 1.60GHz
stepping    : 2
cpu MHz        : 1595.966
cache size    : 512 KB
physical id    : 0
siblings    : 4
core id        : 1
cpu cores    : 2
apicid        : 3
initial apicid    : 3
fdiv_bug    : no
hlt_bug        : no
f00f_bug    : no
coma_bug    : no
fpu        : yes
fpu_exception    : yes
cpuid level    : 10
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca 
cmov pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm 
constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl 
tm2 ssse3 cx16 xtpr pdcm movbe lahf_lm
bogomips    : 3192.06
clflush size    : 64
cache_alignment    : 64
address sizes    : 32 bits physical, 48 bits virtual
power management:

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