Re: [Discuss-gnuradio] NTSC Demo

[Thom Rainwater]

> > > >
> > >     
> >   
> If I understand it well you do the following to get rid of the audio_carrier:
> interpolate 2x to avoid aliasing
> downconvert audio-carrier to zero
> highpass to get rid of audio-carrier
>
>
>
> downconvert video-carrier to zero
> get absolute value(get envelope)
> decimate 2x
>   
>
> The above steps can be done in gnuradio with the components which are already 
> there
> interpolator
> freq_translating_fir_filter  (which you feed  high_pass fir filter taps)
> multiplication (or another freq_translating_fir_filter with low_pass filter 
>
>
>
> taps, this way you get a band_filter)
> abs
> decimator

Is there a way to get these same results w/o interpolating the entire signal? See attached diagram. Can we assume that the significant spectrum of the video component is less than 4 MHz? If so, can we take the incoming signal sampled at 8 MS/s complex do our audio processing to get the audio signal, then filter out audio component, translate the video component and do the video demod?

Thanks

Thom Rainwater

diagram.png
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