IÂ´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 donÂ´t have HDTV broadcast signal in BrasÃlia. 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 couldnÂ´t run his application. And Prateek have been working with chrominance, in matlab, but doesnÂ´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 180Âº, that is +I and -I. The Q inversor also supplies two Q signals with a difference between them of 180Âº. Is it right? Does anyone know any other project that decodes NTSC signals in software? I would appreciate some help I can get. Thanks. __________________________________________________ Fale com seus amigos de graÃ§a com o novo Yahoo! Messenger http://br.messenger.yahoo.com/
on 2007-05-19 21:35
on 2007-05-20 07:40
> 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. I don't understand what you are asking. What did you conclude? What do you need help with? What do you need confirmation on? Perhaps we can talk off list (in spanish). > 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? The script you are talking about is trying to implement a black and white television. It is by definition luminance only. > From what I found out, > Daniel G. is working in an implementation of > synchronization I did write a couple of different versions of the sync detector. Each of them had its own problems. > but I couldn´t run his application. Why could you not run it? Did it compile? Does they example run and you get no output (ie black screen)? What was the compile error or program output on the console? What did you use for a signal? Was it an antenna? Did you use a cable television signal? Did you use a modulated output from a VCR or similar device? > 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? You may have some trouble using the MATLAB based approach Prateek used for chrominance detection; it is not easily ported to GNU Radio as a block. You must reliably detect the phase of the chroma burst for every line. There may already be a PLL block in GNU Radio but I don't know what it is called. > stream of floating points. This demodulated signal > difference between them of 180º. You've got the main idea down well except for the filtering part. Your explanation is confusing. Regards, Daniel ____________________________________________________________________________________Get the free Yahoo! toolbar and rest assured with the added security of spyware protection. http://new.toolbar.yahoo.com/toolbar/features/nort...