[mythtv-users] saa7134, bt878, on-board audio and recording profiles

James Klaas jklaas at appalachian.dyndns.org
Tue May 8 16:05:32 UTC 2007

It seems like this isn't an entirely unknown problem.  I finally hit
upon the correct set of search words for google on this issue and came
up with some others who have had the same issue.  Ed Windes mentioned
the very same problem and possible solution over in the mythtv-dev
list:  http://www.gossamer-threads.com/lists/mythtv/dev/255032.

In his reply, Michael T. Dean mentions that "It's playback--not
recording--where there's "disagreement"."  Unfortunately, that seems
incorrect by my own experience.  Setting the audio rate in both the
recording profile and in capturecard to 32000 allows my saa7134 based
card to record correctly, but my other recordings get a low throbbing
hum.  And, of course, setting the audio rate to 48000 causes the
saa7134 recordings to sound like chipmunks (with associated speed up
in video since the video is synced to the audio).  It doesn't make
sense to me at all that "it's playback" since transcoding these
recordings to some other format has the same problem.

Michael, would you be willing to make a proper patch diff for your
stuff?  Something like:

diff -urp original_directory new_directory > filename.patch


On 5/7/07, Michael Lynch <lynchmv at gmail.com> wrote:
> I feel your pain...
> http://www.gossamer-threads.com/lists/mythtv/users/236333?#236333
> http://www.mythtv.org/wiki/index.php/User:Lynchmv
> I have my patches if you are feeling adventurous (see my wiki page).
> It's been a while since I created/applied the patches, but it's been
> working great for me as far as recording and getting the proper sound
> setup.  The patches allow for 3 different V4L cards.  A standard v4l
> profile, a 32khz v4l profile and a 48khz v4l profile.
> On 5/7/07, James Klaas <jklaas at appalachian.dyndns.org> wrote:
> > I have a mythtv master backend with two tuners, an saa7134 and a
> > bt878.  I've finally figured out how to get all the hardware to record
> > correctly.  I must load the saa7134 drivers first, otherwise the tuner
> > doesn't work.  But I've run into another, extremely frustrating
> > problem.
> >
> > Since I'm using the audio output from the saa7134, it's capture rate
> > must be 32000.  I made sure that the audioratelimit was set to 32000
> > when I set up the card in mythtv-setup.  However, I kept getting
> > chipmunk audio.  After tearing out my hair for a couple weeks, I
> > finally found a note pointing to setting up the audio rate in
> > recording profiles.  No problem, I thought, I'll just set the audio
> > rate in recording profiles.  Ooops.  No go.
> >
> > When recording from the bt878 board which has analog audio going
> > through the nVidia on-board audio I get a low pulsing hum on
> > recordings made at 32000 through the on-board audio.  So, the onboard
> > audio seems to require an audio rate something other than 32000.
> > Thus, I have reached Catch-22, and lack of hair.
> >
> > I was hoping there would be some way to set the audio rate for
> > recording profiles to match the hardware it's recorded on.  If that's
> > not possible, then what is the point of asking for the audio rate
> > limit when setting up the card?  It seems to just be ignored.
> > Certainly someone out there has run into this issue before.
> >
> > James
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> >
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