[mythtv] MythTV - No Picture

[Bruce Markey]

Bryce C wrote:
> Then why can xawtv seem to?  So can xmms etc.  "lsof /dev/sound/*
> /dev/dsp*" shows nothing and even running it as root doesn't fix it.

Xawtv is simply using the the analog sound patched through
line-in to line-out. It doesn't need to digitize the sound
unless you are recording.

A better test to verify that sound will work for MythTV (and
recording with xawtv for that matter) is the startup xawtv,
mute the line-in then run "aplay /dev/dsp". Once this test
succeeds, MythTV should also work correctly because it writes
to, and read from /dev/dsp in the same way.

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 audio 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 needed
in alsamixer:

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 on 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.

Capture mixer - this sets the level for the analog to digital
recording. While a volume of 100% is recommended for testing,
distortion may occur. Lowering this level to 75% to 85% may
result in better audio quality. "Capture" should be marked as
the CAPTUR destination.

PCM mixer - this sets the level for the digital to analog
playback. While a volume of 100% is recommended for testing,
distortion may occur. Lowering this level to 75% to 85% may
result in better audio quality.

Master mixer - sets the level for the analog signal sent to
line-out or the speakers.

--  bjm