[linux-dvb] Tuner not detected on second Kworld card

CityK CityK at rogers.com
Sun Oct 14 21:34:08 CEST 2007


David Engel wrote:
> The minor problem I mentioned earlier has to do with using the
> saa7134-alsa module to capture sound directly from the card.  A quick
> glance at the driver source code looks like it shold support 32 and 48
> kHz sampling rates.  I've only been able to get 32 kHz working well so
> far with MythTV.  Trying 48 kHz results in some sort of rate mismatch.
> Is 48 kHz supposed to work?
...
> I tried using mplayer with 48 kHz audio and got the same results.
> Regardless of the requested audio rate, the cx88-alsa driver or
> hardware only supplies 32 kHz audio.  The result is audio underruns
> and chipmunk audio because the samples that are received are being
> played too fast.  Can anyone confirm the Kworld card can only do 32
> kHz?

I could have sworn I just wrote about this -- email? wiki? But alas, I
can't find a thing. In any regard ...

Yes, you can only use 32KHz from the tuner with the saa713x. This is a
hardware limitation of the chip in regards to handling of SIF sources.
For further information, search through the V4L achieves using various
"saa7134" or "saa713x" and "32KHz" and "alsa" combinations. There should
be plenty of good info. (Example:
http://marc.info/?l=linux-video&w=2&r=1&s=32KHz+saa7134&q=b)

However, that said, I'm just thinking aloud here about this case, as
this actually presents a curious question. Here goes:

The NIM on these boards (TUV1236D) contains a TDA9887, which is capable
of SIF demodulation, and hence, if utilised, would be feeding the
saa713x a baseband audio signal for ADC. Yet, given that in field
testing shows the 32KHz limitation, it would seem to indicate that the
SIF capability of the TDA9887 is being ignored and that, instead, the
broadcast audio is being sent straight to the saa713x for processing
(ie. tuner -> saa713x for SIF demod & then ADC).

I'm wondering if this is a case of:
(1) hard wiring from the TUV1236D module (broadcast audio output) to the
saa713x
or
(2) if there exist alternate pathways/routes in the TUV1236D for the
audio signal i.e.:
(i) tuner -> TDA9887 for SIF demodulation -> baseband audio to saa713x
for ADC
(ii) tuner -> saa713x for SIF demod & then ADC

If it is a case of 2), then it is obvious that the later route (ii) is
being utilized ... and, if it is a case of 2), then the obvious follow
up question is: How do you enable the more desirable pathway (i) ? ...
i.e. make use of the TDA9887 for SIF demodulation and feed the resultant
baseband signal to the saa713x, which, consequently, would allow for the
selection of sampling rates other then 32KHz during the ADC phase.










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