[pulseaudio-discuss] problems with KWorld DVB-T 323UR tuner sound quality&volume

[Tanu Kaskinen]

pe, 2009-07-10 kello 10:13 +0300, Laszlo Kustan kirjoitti:
> Hi to everyone,
> I have a Kworld DVB-T 323UR hybrid tuner connected to my Linux Mint
> Gloria (based on Ubuntu Jaunty).
> I route the sound from it the following way:
> arecord -D hw:1,0 -c 2 -r 48000 -f S16_LE | aplay -
> 
> The problems are:
> - background noise and sound is almost muted, I can hardly hear the
> sound with the speakers turned to max volume.

Assuming that other sound producing programs output with a normal
volume, the tuner record level (and/or its master volume) is probably
low. Run "alsamixer -c1" to find out and fix the situation. If this is
not the problem, I don't know what might be.

An addition: I just noticed that you claimed the mixer settings seemed
fine. Did you perhaps only look at the sound card mixer and not the
tuner's mixer? Have you noticed that alsamixer shows mixer controls
separately for playback and record? The mode can be switched with the
tab key. With the tuner you're interested only in the recording
controls, maybe except for the Master control which might also affect
recording levels (or might not, I don't really know if it's possible).

> - slight delay between A/V

It seems that this kind of hook-tuner-to-sound-card setup is rather
common with analog tv cards. In this situation the playback program has
no information about how audio and video should be synchronized.
Therefore I would guess that tvtime would offer the possibility to add
delay to the video playback. I've never used the program, so I don't
know if that's the case.

If a delay can't be added, you can only try minimizing buffering (which
may cause drop-outs). aplay and arecord seem to have several buffering
options, --buffer-time being perhaps the easiest to use. I assume aplay
in your example plays through pulseaudio - I don't know how well the
buffer size request is respected by the pulse alsa plugin.

> - sometimes when I stop the sound routing (pressing Ctrl-C in the
> terminal) the whole system hangs up.

Hangs up as in you need to reboot? I don't know what might cause that -
maybe a buggy sound card or tuner driver?

A fourth problem that you didn't mention, but I think is quite likely to
occur, is that raw piping from the tuner to the sound card causes
glitches as the tuner and the sound card don't share the clock and due
to clock drift you get buffer over- or underruns. I don't know any good
solution for this.

-- 
Tanu Kaskinen