[mythtvnz] Various MythTV issues

[Nick Rout]

On Tue, July 31, 2007 8:13 am, Hadley Rich wrote:
> On Mon, 30 Jul 2007 22:53:21 David Nock wrote:
>> Hi all,
>>
>> I'm slowly finding the time to get our MythTV box up and running.
>>
>> The biggest problem at the moment is I cannot get the audio working wh=
en
>> watching tv. Current hardware is a Shuttle ST61G4 and a Pinnacle PCTV
>> Pro tuner card. This tuner has an audio out connection that I have
>> patched back into the line input of the Shuttle but so far cannot get
>> the audio through MythTV.
>>
>> I have verified that I can get audio out of the Shuttle using MythMusi=
c
>> and that works fine. Also, I have plugged headphones directly into the
>> tuner card and the audio is there. I've also tried adjusting the volum=
e
>> levels using aumixer but so far no go.
>>
>> Currently in the myth settings the audio is configured to come from
>> /dev/dsp.
>>
>> Another thing, when listening to the audio directly from the card, it =
is
>>   badly out of sync with the picture. I'm assuming this is because of
>> the buffering MythTV is doing and hoping that when I can get the audio
>> sorted, this won't be a problem.
>>
>> Would appreciate any ideas that people have.
>
> You assume correctly. The sound is out of sync as you are listening to =
the
> sound directly from the card but you should be listening it from the fi=
le
> mythtv creates on the hard disk (normally 2-5 seconds behind).
>
> I don't know anything about setting up framegrabber cards and I'd
> recommend
> getting a PVR150 card instead.
>
> At a guess I'd imagine you need to unmute something on your mixer
> (line-in?)
> and mute something else.

Actually the problem is dealt with in TFM :-)

http://www.mythtv.org/docs/mythtv-HOWTO-7.html

If your video doesn't appear to be in-sync with your audio and you're
using an analog video capture card and a soundcard to capture audio, it
could be because you are listening to the real-time audio from your video
card rather than after it's been processed and synchronized to the video
by MythTV. Because MythTV is a personal video recorder, "Live TV" isn't
really live - to let you pause live TV, MythTV is actually encoding the
video, saving to disk, and then playing it back. This procedure puts your
MythTV "live" TV about 2 seconds behind real-time, so it's important that
you're not listening to the live audio. ... See the Troubleshooting Audio
section for more information if you're having issues with sound.

http://www.mythtv.org/docs/mythtv-HOWTO-22.html#Troubleshooting_Audio

To record audio along with video the audio signal must be digitized by a
DSP so that the audio data can be stored in a file. On playback, the audi=
o
data is written to /dev/dsp and converted back to an analog signal. This
analog signal should then be sent to your speakers. Here is what is neede=
d
in alsamixer. If you are using an ALSA version after 1.0.6, use alsamixer
-V all:

CAPTUR source - the analog source to be sent to the DSP. This should be
set to the input source from the tuner card to the sound card. In most
cases this is Line but this could also be Aux, CD, Mic, etc., depending o=
n
how you connect the input cable. This source should be muted to prevent
patching through the analog sound. The volume of this source will not
affect the record level.

--=20
Nick Rout