Gnu Radio NTSC process

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 G. 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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