[mythtv-users] HDTV Playback Audio Juddering Problem, PBS HD only

John Freer john_freer at yahoo.com
Sun May 1 16:10:45 UTC 2005


Hi all,

Having a problem playing back the audio on my local ATSC PBS HD
station.  I'm doing S/PDIF with AC3 pass through.  Works great on
ABC, NBC, CBS, etc.  For example, I watched harry potter last night
on ABC, and it played back great with DD content, etc.

I'm experiencing "juddering audio".  When someone's talking on screen
it sounds like when Chris Farly says "Luke, you are my father" into
the fan in Tommy Boy.  Weird.  CPU averages 25% free.  XP2600 400FSB,
8X AGP MX440, 7174 Drivers.  No XvMC.  Content plays back fine so
long as I'm not recording with a bttv card or flagging in the
background.

I'm using ALSA:default as the output device, and using the .asoundrc
that's on the digital sound howto.  Other than that, just using
up-to-date mythtv rpms.

Here's my --verbose playback,audio log snippets:

**********************************************************************
[mythtv at numbernine ~]$ more frontend.log 
2005-05-01 12:00:50.557 New DB connection, total: 1
Total desktop width=1024, height=768, numscreens=1
2005-05-01 12:00:50.563 Using screen 0, 1024x768 at 0,0
2005-05-01 12:00:50.593 mythfrontend version: 0.18.20050409-1
www.mythtv.org
2005-05-01 12:00:50.593 Enabled verbose msgs : important general
playback audio
2005-05-01 12:00:51.257 max_width: 1024 max_height: 768
2005-05-01 12:00:51.314 Switching to square mode (Titivillus)
2005-05-01 12:00:52.721 Joystick disabled.
2005-05-01 12:00:52.738 New DB connection, total: 2
2005-05-01 12:00:52.879 Registering Internal as a media playback
plugin.
2005-05-01 12:00:52.985 Registering MythDVD DVD Media Handler as a
media handler
2005-05-01 12:00:52.986 Registering MythDVD VCD Media Handler as a
media handler
2005-05-01 12:00:54.094 Registering MythMusic Media Handler as a
media handler
2005-05-01 12:01:10.661 All Programs
2005-05-01 12:01:11.011 Connecting to backend server: 127.0.0.1:6543
(try 1 of 5)
2005-05-01 12:01:11.019 Using protocol version 15
2005-05-01 12:01:15.612 AVFD
2005-05-01 12:01:15.612 AVFD: Opening Stream #0: codec id 2
2005-05-01 12:01:15.614 detectInterlace(Detect Scan, Detect Scan,
29.97, 1088) ->Interlaced Scan
2005-05-01 12:01:15.614 Interlaced: Interlaced Scan  video_height:
1088  fps: 29.97
2005-05-01 12:01:15.614 AVFD: Looking for decoder for 2
2005-05-01 12:01:15.614 AVFD
2005-05-01 12:01:15.614 AVFD: Opening Stream #1: codec id 86020
2005-05-01 12:01:15.614 AVFD: Looking for decoder for 86020
2005-05-01 12:01:15.616 Stream #1 (audio track #0) is an audio stream
with 2 channels.
2005-05-01 12:01:15.616 Auto-selecting AC3 audio track (stream #1).
2005-05-01 12:01:15.616 Initializing audio parms from audio track #0.
2005-05-01 12:01:15.618 Estimated bitrate = 19784
2005-05-01 12:01:15.662 Position map filled from DB to: 49070
2005-05-01 12:01:15.663 SyncPositionMap prerecorded, from DB: 3399
entries
2005-05-01 12:01:15.663 SyncPositionMap, new totframes: 49070, new
length: 1637, posMap size: 3399
2005-05-01 12:01:15.735 Position map found
2005-05-01 12:01:15.747 Killing AudioOutputDSP
2005-05-01 12:01:15.748 Opening audio device 'default'.
2005-05-01 12:01:15.953 in SetParameters(format=2, channels=2,
rate=48000, buffer_time=500000, period_time=125000)
2005-05-01 12:01:15.954 get_buffer_size returned 16384
2005-05-01 12:01:15.955 set_period_time_near returned 85333
2005-05-01 12:01:15.955 get_period_size returned 4096
2005-05-01 12:01:15.955 Audio fragment size: 4096
2005-05-01 12:01:15.956 Audio Stretch Factor: 1
2005-05-01 12:01:15.957 Ending reconfigure
2005-05-01 12:01:15.958 kickoffOutputAudioLoop: pid = 17030
2005-05-01 12:01:15.958 OutputAudioLoop: Play Event
2005-05-01 12:01:15.958 Broadcasting free space avail
2005-05-01 12:01:15.962 Broadcasting free space avail
2005-05-01 12:01:15.974 Over/underscan. V: 0, H: 0, XOff: 0, YOff: 0
2005-05-01 12:01:15.980 Using XV port 107
2005-05-01 12:01:15.985 Image size. dispxoff 0, dispyoff: 96,
dispwoff: 1024, disphoff: 576
2005-05-01 12:01:15.985 Image size. imgx 0, imgy: 0, imgw: 1920,
imgh: 1080
2005-05-01 12:01:15.986 Broadcasting free space avail

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

And then this stuff just repeats forever:

*****************************************************************
2005-05-01 12:01:17.296 A/V diverged by 3.66391 frames, extending
frame to keep audio in sync
2005-05-01 12:01:17.297 Broadcasting free space avail
2005-05-01 12:01:17.297 WriteAudio: Preparing 4096 bytes (1024
frames)
2005-05-01 12:01:17.297 audio waiting for space on soundcard: have
704 need 4096
2005-05-01 12:01:17.298 _AddSamples bytes=6144, used=104449,
free=407551, timecode=94617749
2005-05-01 12:01:17.298 _AddSamples bytes=6144, used=110593,
free=401407, timecode=94617774
2005-05-01 12:01:17.304 audio waiting for space on soundcard: have
2016 need 4096
2005-05-01 12:01:17.311 audio waiting for space on soundcard: have
3360 need 4096
2005-05-01 12:01:17.318 Broadcasting free space avail
2005-05-01 12:01:17.318 WriteAudio: Preparing 4096 bytes (1024
frames)
2005-05-01 12:01:17.318 audio waiting for space on soundcard: have
640 need 4096
2005-05-01 12:01:17.321 _AddSamples bytes=6144, used=112641,
free=399359, timecode=94617781
2005-05-01 12:01:17.321 _AddSamples bytes=6144, used=118785,
free=393215, timecode=94617806
2005-05-01 12:01:17.329 A/V diverged by 6.05218 frames, extending
frame to keep audio in sync
**********************************************************************

Thanks,
John.


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