Re: [Discuss-gnuradio] Re: Increasing ALSA Sampling Rate

[George S. Williams]

Hey, Patrick,

I found the idea in this post to the list-
http://www.mail-archive.com/address@hidden/msg28487.html

which led to this-
http://hackaday.com/2005/11/08/using-a-tv-tuner-as-a-high-speed-adc/

which led to this-
http://www.domenech.org/bt878a-adc/index-e.htm

The cards are old PV-BT878P+ analog video cards. I found 2 on ebay for 
about $10US each- a Rev-9D, which is the one described in the article, 
and a Rev-10A. The card for the Rev-10A is a bit different, but the same 
connection from the tuner module is used in the modification. I have 
both cards working with GNU Radio at 896000. (And apparently working 
with ALSA at 1792000)

The article is a bit dated- the current ALSA interface is the snd-bt87x 
module instead of the old btaudio module. But the modification to 
aplay.c is the same. The  Bt87x Audio Capture kernel module will need to 
be recompiled with the Bt87x Audio overclocking option set (if it isn't 
already) in order to go from 448000 to 896000 or 1792000.

This should be enough to give you the basic idea.

Later,
George


On 2/1/2011 6:07 AM, Patrick Strasser wrote:
> schrieb George S. Williams am 2011-01-27 17:38:
> > Is it possible to increase the maximum sampling rate for audio_alsa?
> >
> > I am experimenting with using a modified TV tuner card as an ADC. The
> > card uses a Bt878a chipset. arecord can record from the card at 1972000
> > rate and GRC shows the maximum rate as 1972000, but GNUradio can only
> > sample at 896000.
>
> 896kSPS is quite something. Can you tell more about the hardware? I at
> least (and probably many others) am very interested in something like this.
>
> Regards
>
> Patrick