[mythtv-users] Audio tuning advice needed
hakon at alstadheim.priv.no
Tue Jun 10 08:14:53 UTC 2008
Lonnie Borntreger wrote:
> Got a question dealing with the tuning of the capture - as related to
> the audio part.
> Occasionally, a show will "pump the volume" and it results in "choppy"
> audio... kind of like something is "clamping" the level.... like a
> automatic gain control. Is there something I can change in the stream
> encoding options in MythTV to eliminate this, or is it completely
> hardware/driver related?
> Oh, I have all PVR-500s (one Philips, one Samsung) - but they both
> have this same issue. Like I said, it doesn't happen often, but it's
> really annoying when it does.
> Lonnie Borntreger
In my experience that is most likely a weak/noisy signal resulting in
rapid switching between mono and stereo. This could also be a driver
issue, either a bad tuning algorithm or a too trigger-happy switching
between mono and stereo. I have resorted to forcing mono. For me in
Norway using the saa7134 driver, the incantation involves putting
options saa7134 audio_ddep=4
into /etc/modprobe.conf. The exact value depends on what tv-standard you
are receiving. Take a peek in the source, or just run through a series
of edit/modprobe/dmesg -c/rmmod, going throug all the values. The dmesg
will tell you how the parameter is interpreted, at least if you set
audio_debug=2 in the options.
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