[mythtv-users] "Squeaky" audio when using Plextor M402U
Rod Smith
mythtv at rodsbooks.com
Mon Apr 2 02:39:53 UTC 2007
On Sunday 01 April 2007 20:08, Chris DiLorenzo wrote:
> I'm using a Plextor M402U to capture from DirecTV. I am running Gentoo
> with the 2.6.18 kernel. I patched the Go7007 drivers and was able to build
> them with no problems. When I use the gorecord application, I am able to
> capture video with no problems.
>
> However, when I use MythTV (ver 0.20) I can capture shows, but the sound is
> horrible. There is this annoying high pitched hum or squeak and the voices
> are distorted. It is not my frontend system since the distortion occurs
> when I play the files with mplayer directly on the bcakend.
...
> If you want to hear an example, you can download a nuv from
> http://home.comcast.net/~dilorc/Bad_MP3.nuv
That sounds very similar to the problem I had with an AVerMedia AVerTV M150-D,
which is a PCI MPEG-2 capture card. I eventually found a solution, as
detailed on the MythTV wiki entry for that card and on the MythTV wiki sound
troubleshooting page:
http://www.mythtv.org/wiki/index.php/AVerMedia_M150-D
http://www.mythtv.org/wiki/index.php/Sound_Troubleshooting
In brief, the solution was to use an external channel-change command that uses
v4lctl to do the job. I hypothesize that the stream provided by the card
becomes unstable when the channel changes and that MythTV tries to access the
data stream too soon, causing it to corrupt the audio for the rest of the
recording. Using an external tuning command introduces enough delay to
correct the problem. This is, however, just speculation on my part, and I
can't be sure that you're seeing the same problem. If my fix does the job for
you, though, I encourage you to edit the sound troubleshooting wiki entry
appropriately and add a note about this to the M402U entry (there are two,
actually; one is titled for the Plextor ConvertX).
--
Rod Smith
http://www.rodsbooks.com
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