[pulseaudio-discuss] redirecting audio from SAA7134 tv card

Lennart Poettering lennart at poettering.net
Fri Oct 2 01:11:08 PDT 2009

On Thu, 01.10.09 12:38, Luca DELLA GHEZZA (luca_dgh at hotmail.it) wrote:

> I can ear the tv audio from the standard output. That is fantastic,
> because I tried as well with the BT headset and it works.
> Sadly the audio has a very poor quality:
> 1) the audio is pulsing, it seems that it pump up and down the master
> volume

Uh? You say the volume changes all the time? That is weird. Maybe this
is due to reception quality?

Does this alos happen if you use this loopback stuff for your webcam mic?

> 2) the rate is wrong, because it seems an old 33 rpm listening at
> 45.

Hmm, that is interesting. We actually resample the stream as necessary
to deal with clock deviations between the sink and the source. On
crappy devices where the timing interfcae is broken that might cause
some weird effects. Now for the SAxxx TV drivers it is a fact that the
driver is crappy. For example, it already chokes when we skip
configuration of a hw buffers size/period size.

Normally, the rate should stabilize after a while even on crappy
devices. You might be able to improve behaviour by playing around with
"adjust_time" (increase it to 30 or so...)

> When I use sox to redirect audio it needs to set the rate to 32000, but
> in this case has no effect.
> I use s16le format because I know that the format used from the tv card
> is Signed Little Endian 16 bit.
> Finally I tried to change the latency to 1 and as well to 2000 but
> nothing change, or very little changes.

Yes, this is simply a hint. If the underlying devices cannot do this
the actual measured latency might deviate substantially, both upwards
and downwards. This is expected.

> I need different settings or may be I need to change the sink
> device?

Normally, you shouldn't need any settings.


Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4

More information about the pulseaudio-discuss mailing list