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

[Tanu Kaskinen]

la, 2009-07-11 kello 00:44 +0300, Laszlo Kustan kirjoitti:
> Hi,
> Thanks for your answer.
> 
> > 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.
> 
> Yes, other sounds are ok. The difference between the sound levels is
> big, I must turn off all other sounds when watching TV because other
> sounds are much louder (as my speakers are at max volume level).
> alsamixer -c1 says "No mixer elems found".

If the driver doesn't expose any mixer elements, you're probably out of
luck with that tuner, as there's absolutely no way to control the volume
(unless the device provides some other interface than alsa to control
it).

> > 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.
> >
> I already tried sox with minimum buffering and the delay was the same.

In case pulseaudio buffering doesn't equal to that what alsa clients
request, you could try bypassing puseaudio by running the playback
program (aplay or sox) with pasuspender, for example

arecord -D hw:1,0 -c 2 -r 48000 -f S16_LE --buffer-time=50000 |
pasuspender -- aplay -D front:0 -c 2 -r 48000 -f S16_LE
--buffer-time=50000

(That's supposed to be one line. Recording and playback both use 50ms
buffering in this example.)

> > 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.
> yes, there are glitches too, but with the background noise I have they
> are not so annoying.
> This means that no usb tuner can work normally under Linux? I did not
> see so much complaints on forums, so I guess most of the people can
> use normally their tuners.

I'm not familiar with analog tuners, but if the sound has to be routed
from the tuner to a sound card, I don't see any way around this problem
(not that it's not solvable, just that I'm not aware of any existing
solutions). But if the tuner, USB or whatever, provides a line-out port
(or something similar), then the speakers can of course be hooked to
that just fine. Maybe most of tuners offer that and users are generally
happy with it? (Occasionally analog tuner users ask here how to route
line-in to line-out after they hook the tuner to the sound card using a
cable.)

> I also wrote to the linux-dvb mailing list and according to them tuner
> driver seems to work correctly at me, the problems should be
> pulseaudio related.

It seems that your problems have very little to do with pulseaudio,
since (at least in the example) you record directly from the tuner,
instead of through pulseaudio. Only the delay issue may have something
to do with pulseaudio.

-- 
Tanu Kaskinen