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

hermann pitton hermann-pitton at arcor.de
Mon Oct 15 00:18:11 CEST 2007


Am Sonntag, den 14.10.2007, 15:34 -0400 schrieb CityK:
> 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.

Limitation is, that there is no direct stereo TV sound output from those
tuners.

The saa7130 chip uses always baseband audio from the tuner and has no
audio ADCs. That,s why no dma sound is supported and always a
loopthrough connection to the sound card is needed and why it has only
mono TV sound. Radio and other analog inputs can be stereo. DVB just
gets pumped through the TS interface and the dma engines.

The saa7134 chip has no stereo audio support for System M and the
saa7133 has no support for dual FM (A2) stereo.

Currently only saa7135 and saa7131e support all kind of TV sound.
The two others could utilize additional SIF/MPX sound decoding chips,
then your scenario would become true. Suggested as a solution in such
case, but not yet seen.

How to make use of which audio coming from the tuner also depends of the
audio system in use. For example think about mono on the first sound
carrier and NICAM on the second. You will need the saa713x NICAM decoder
to get stereo sound.

On the Philips MultiEurope MK3s with tda9887 only radio comes stereo
separated by the tda7040 to either the LINE1 or LINE2 pair of analog
inputs.

If switched back to TV mode, you get from those two lines equal TV mono
audio, also about 6 db lower as otherwise, IIRC.
Some cards still use a TV mono section with vmux TV and same amux than
used for radio exactly for that reason, as workaround for having
problems with stereo sound in the beginnings. That is also what you see
on the saa7130 chips.

If needed, we might continue on the video4linux-list ...

The other issue sounds a bit weired or my poor English fails.
Multiple identical cards should be auto detected like they are found
walking down the PCI devices and lining up minors.

Cheers,
Hermann










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