[mythtv-users] WriteAudio: buffer underruns without prebuffering pauses

[Tom Greer]

I have a problem in HD playback that I need help to solve.

My basic problem is that the audio frequently stutters.  My log is filled
with messages that say "WriteAudio: buffer underrun".

Searching the mailing list archive, I find references to this problem.  In
each case these messages are linked to prebuffering pauses - and the
recommended solutions seem to be focused on fixing the prebuffering pauses
and the audio stutter will be fixed as well.

My audio buffer underruns are not linked to prebuffering pauses. Here is a
pertinent snippet from my frontend log.

2007-02-18 23:41:20.612 TV: Changing from None to WatchingPreRecorded
2007-02-18 23:41:20.669 Realtime priority would require SUID as root.
[mpeg2video @ 0x364d4db050]ac-tex damaged at 92 20
[mpeg2video @ 0x364d4db050]Warning MVs not available
2007-02-18 23:41:20.810 Video timing method: SGI OpenGL
[mpeg2video @ 0x364d4db050]invalid mb type in B Frame at 114 49
[mpeg2video @ 0x364d4db050]Warning MVs not available
2007-02-18 23:41:23.507 WriteAudio: buffer underrun
2007-02-18 23:41:27.305 WriteAudio: buffer underrun
2007-02-18 23:41:29.270 WriteAudio: buffer underrun
2007-02-18 23:41:31.301 WriteAudio: buffer underrun
2007-02-18 23:41:34.594 WriteAudio: buffer underrun
2007-02-18 23:41:36.323 WriteAudio: buffer underrun
[mpeg2video @ 0x364d4db050]ac-tex damaged at 39 10
2007-02-18 23:41:39.777 WriteAudio: buffer underrun
2007-02-18 23:41:41.373 WriteAudio: buffer underrun
[mpeg2video @ 0x364d4db050]00 motion_type at 66 14
2007-02-18 23:41:44.370 WriteAudio: buffer underrun
2007-02-18 23:41:45.487 WriteAudio: buffer underrun
2007-02-18 23:41:48.358 WriteAudio: buffer underrun
2007-02-18 23:41:50.817 WriteAudio: buffer underrun
2007-02-18 23:41:53.534 WriteAudio: buffer underrun
2007-02-18 23:41:56.175 WriteAudio: buffer underrun
[mpeg2video @ 0x364d4db050]00 motion_type at 28 45
2007-02-18 23:41:57.114 WriteAudio: buffer underrun
[mpeg2video @ 0x364d4db050]ac-tex damaged at 56 37
[mpeg2video @ 0x364d4db050]Warning MVs not available
2007-02-18 23:41:59.323 WriteAudio: buffer underrun
2007-02-18 23:42:01.180 WriteAudio: buffer underrun
2007-02-18 23:42:03.520 WriteAudio: buffer underrun
2007-02-18 23:42:05.108 WriteAudio: buffer underrun
2007-02-18 23:42:06.466 WriteAudio: buffer underrun
2007-02-18 23:42:09.106 WriteAudio: buffer underrun
2007-02-18 23:42:11.261 WriteAudio: buffer underrun
2007-02-18 23:42:12.479 TV: Attempting to change from WatchingPreRecorded to
None

Here is a brief description of my setup.

My frontend runs on a AMD64 Sempron 2800+ with 1 gb of RAM and an NVIDIA
FX-5200 video card.
My backend runs on a similar machine AMD64 Sempron 2800+ with 1 gb of RAM
and an NVIDIA FX-5200 video card.
My recordings are stored on an Ubuntu LAMP server in the closet.

My frontend is configured with Standard MPEG decoder and the BOB deinterlace
algorithm.  For HD playback, my CPU utilization runs about 90%.

I have tried XVMC. My CPU utilization drops to 20-30%; but the audio stutter
does not go away.

Turning off deinterlacing yield no improvement either.  I have also tried
all of the other deinterlace algorithms.  No difference.

Here are the important sections of my xorg.conf:

Section "Module"
    Load  "dbe"
    Load  "extmod"
    Load  "fbdevhw"
    Load  "glx"
    Load  "record"
    Load  "freetype"
    Load  "type1"
EndSection

Section "Monitor"
    Identifier   "Monitor0"
    VendorName   "Panasonic"
    ModelName    "42in EDTV"
    ModeLine     "ATSC-1080-60i" 74.2 1920 1960 2016 2200 1080 1082 1088
1125 interlace
    Option        "dpms"
    Option        "UseEdidDpi" "False"
    Option        "DPI" "100 x 100"
EndSection

Section "Device"
    Identifier  "Videocard0"
    Driver      "nvidia"
    Option        "UseDisplayDevice" "DFP"
    Option        "NVAGP" "2"
    Option        "XvmcUsesTextures" "True"
    Option        "UseEvents" "True"
    Option        "ConnectedMonitor" "DFP"
EndSection

Section "Screen"
    Identifier "Screen0"
    Device     "Videocard0"
    Monitor    "Monitor0"
    DefaultDepth     24
    SubSection "Display"
        Viewport   0 0
        Depth     24
        Modes    "ATSC-1080-60i"
    EndSubSection
EndSection

Any help is appreciated.

Tom
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