[mythtv-users] Using btaudio

[David Tarkowski]

* Chuck Lloyd (clloyd at lloyd.dyndns.org) [030227 21:51]:
> I've had a similar experience with my WinTV GO. My guess
> is that if the card doesn't advertise that it supports
> stereo, then the digital stereo input doesn't work.

The card that I am using is the AverTV Stereo, so it should support the
digital interface.  The documentation for btaudio says that the rate
parameter to the module might help, but I've tried all of the logical rates
that I could think of without success.

> I had similar experience with the crappy analog audio.
> I think it is a mismatch in the sampling rates. I found
> that the sound was good if I oversampled with sox.
> 
> 	http://lloyd.dyndns.org/index.php?Btaudio%20installation
> 
> I was working on a code fix to do a simple linear resample.
> I haven't decided whether to put it in the AudioReader thread
> or just outside. 

According to the btaudio doc, the driver supports downsampling to many
standard rates.  I get the same quality no matter what sampling rate I use.
The two main problems are pops and a high frequency hiss.  I've figured out
that the pops were just clipping (I don't understand why there was clipping,
but I can work around it).  

I was playing around last night and was doing some signal analysis of the
signal that I get from the btaudio and I discovered that the frequency
distribtion has two peaks around 15 kHz and 21 kHz IIRC.  The peaks are
actually present in the line in signal, but they are many dB smaller.  I'm
going to play around with some digital filtering this weekend if I get a
chance and how much of a difference that makes.

-Dave


> 
> Chuck
> 
> -----Original Message-----
> From: mythtv-users-bounces at snowman.net
> [mailto:mythtv-users-bounces at snowman.net]On Behalf Of David Tarkowski
> Sent: Thursday, February 27, 2003 8:29 PM
> To: mythtv-users at snowman.net
> Subject: [mythtv-users] Using btaudio
> 
> 
> Hi,
> 
> I noticed in the hardware database that a lot of people are using AverTv
> cards.  I'm using the AverTV stereo card, and was wondering if anybody has
> made it work with the btaudio driver.  I can get sound from the analog
> device, but the digital device doesn't give me anything.  The analog sound
> sounds awful.  Has anybody had more success than me?
> 
> If not, is there a list of hardware anywhere that works well with the
> btaudio driver?  I would really like to do the pausing live TV thing.
> 
> Thanks,
> Dave
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