[mythtv] LiveTV Shuttering & Squeaky Audio

Paul McEnery pmcenery at gmail.com
Wed Jan 31 10:05:53 UTC 2007


> I ran this message for the last couple of days on the mythtv-users
> list, but think it goes a little beyond the scope of normal usage and troubleshooting.
>
> I am running mythtv-trunk r12637 (not particularly relevant) with a DVB-C card (TT C2300).
> I am able to successfully lock onto all channels found during a scan, and 95% of
> the channels play back correctly (livetv & recordings). About a dozen channels
> (out of about 150) are shuttering and the audio is squeaky.


I ran the following tests last night:

I recorded a channel with squeaky audio for a couple of minutes, and
then tried playing it back. The mythtv playback still contained
squeaky audio. I then tried playing the recording back with mplayer.
The audio sounded normal and playback was as you would expect.

A snippet of log output from mplayer for the respective "working" and
"broken" channels appears below. The key difference that I can see is
that channels that work have an audio stream of 192.0 kbit/12.50%
(ratio: 24000->192000). Channels that dont work in MythTV (playback
AND livetv) have 128.0 kbit/8.33% (ratio: 16000->192000).

Am I missing some codec in the compilation of MythTV, or is there a
setting to compensate?


Channel that works:
==========================================================================
Opening video decoder: [mpegpes] MPEG 1/2 Video passthrough
VDec: vo config request - 704 x 576 (preferred colorspace: Mpeg PES)
Could not find matching colorspace - retrying with -vf scale...
Opening video filter: [scale]
The selected video_out device is incompatible with this codec.
Try adding the scale filter, e.g. -vf spp,scale instead of -vf spp.
VDecoder init failed :(
Opening video decoder: [libmpeg2] MPEG 1/2 Video decoder libmpeg2-v0.4.0b
Selected video codec: [mpeg12] vfm: libmpeg2 (MPEG-1 or 2 (libmpeg2))
==========================================================================
==========================================================================
Opening audio decoder: [mp3lib] MPEG layer-2, layer-3
AUDIO: 48000 Hz, 2 ch, s16le, 192.0 kbit/12.50% (ratio: 24000->192000)
Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3)
==========================================================================




Broken channel:
==========================================================================
Opening video decoder: [mpegpes] MPEG 1/2 Video passthrough
VDec: vo config request - 528 x 576 (preferred colorspace: Mpeg PES)
Could not find matching colorspace - retrying with -vf scale...
Opening video filter: [scale]
The selected video_out device is incompatible with this codec.
Try adding the scale filter, e.g. -vf spp,scale instead of -vf spp.
VDecoder init failed :(
Opening video decoder: [libmpeg2] MPEG 1/2 Video decoder libmpeg2-v0.4.0b
Selected video codec: [mpeg12] vfm: libmpeg2 (MPEG-1 or 2 (libmpeg2))
==========================================================================
==========================================================================
Opening audio decoder: [mp3lib] MPEG layer-2, layer-3
AUDIO: 48000 Hz, 2 ch, s16le, 128.0 kbit/8.33% (ratio: 16000->192000)
Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3)
==========================================================================


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