[Discuss-gnuradio] Gnu Radio NTSC processing

[CLEBER CEZAR]

I´m studying the Gnu Radio NTSC processing, by the way to know the processing itself and as a previous work in direction to HDTV signal processing, while we don´t have HDTV broadcast signal in Brasília.

 

I worked with the usrp_tv_rcv.py code, using TVRX and BasicRX daughter boards. From what I could see, I concluded about the project current status, and I would like to confirm this with you. I wonder if someone could help me.

 

The implementation, as it is concerned with the main properties of NTSC signal (chrominance, luminance and synchronization), just works with the luminance. Is it right? From what I found out, Daniel Garcia is working in an implementation of synchronization, but I couldn´t run his application. And Prateek have been working with chrominance, in matlab, but doesn´t have a python version. Is it right? Does anyone know any other work related to implementation of chrominance and synchronization?

 

From the luminance, that is working, I observed that the main blocks implemented in Gnu Radio are:

- gr.agc_cc: it modifies the input signal gain depending on the daughter-board that is used (BasicRX and TVRX). When BasicRX is selected, the gain ranges from 0 to 20 dB. Using TVRX the gain ranges from 0 to 115 dB.

- gr.complex_to_mag: the AM demodulator deals with a stream of complex samples giving an 1-to-1 output stream of floating points. This demodulated signal is received by filters varying from 0 to 1,5 Mhz and from 0 to 0,5 Mhz, with the aim to eliminate sub-products of the demodulation of the I signal above of 1,5 MHz and demodulation sub-products of the Q signal above of 0,5 MHz. 

- gr.add_const_ff: it forces the increase of the black levels in the image. 

- gr.multiply_const_ff: the I inversor supplies two I signals dephased of 180º, that is +I and -I. The Q inversor also supplies two Q signals with a difference between them of 180º.

 

Is it right? Does anyone know any other project that decodes NTSC signals in software?

 

I would appreciate some help I can get. Thanks.

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