Re: [Discuss-gnuradio] Interpolation Issues

[Prateek Dayal]

Hi,

Can you try a few things -->

1. Do not interpolate the signal right now for video ... low pass
filter it with a cutoff of some 3 Mhz and then do an AM demodulation,
extract the timing information and display the monochrome video. It
will not be very sharp but will be good enough

2. Instead of downconverting the audio carrier to the baseband, try
putting a bandpass filter around the audio carrier with a pass band of
arnd 200 kHz .. now if you take the instantaneous phase of this
signal, you will get the phase at baseband + carrier freq. component
..  this carrier freq componenet can be subtracted .... this way not
much computation should be required (by not downconverting) .. this
filtering can be IIR as envelope distortion does not matter here
probably ...

Regards

Prateek

On 6/23/05, address@hidden <address@hidden> wrote:
> Hi,
> 
> In the process of demodulating the video sigal from the tv signal we receive, 
> we
> have been interpolating from 8 MS/s by a factor of 2 to 16 MS/s.  However, 
> just
> demodulating the audio alone takes 97% of our computer's usage, and as soon as
> we interpolate to 16 MS/s the usage peaks at 100% and we get usrp overload
> errors.  Currently our computer's processor is 3.6 GHz.  I was wondering if
> anyone else has come accross computer processing problems when demodulating 
> the
> video.
> 
> thanks
> Brent
> 
> 
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-- 
Prateek Dayal
B.Tech 4th Year
ECE
IIT Guwahati

www.geocities.com/pmd_iitgw