Dear Ron, I have one more question that I hope you can help me with. Here in Hungary the DVB-T broadcast uses Reed-Solomon coding with 188/204 rate. The convolutional coder rate is 3/4. How do I set up the Viterbi decoder, the Convolutional Deinterleaver and the R-S decoder to match these values? When I try to decode the signal received from the nearby station, I see the nice constellation of 64QAM, but the video is not decoded successfully, I cannot play it.
Tibor Herman Tibor <tid...@gmail.com> ezt írta (időpont: 2022. febr. 10., Cs, 12:31): > Hi Ron, > > Thank you for the advice, it's working now! I'll start to construct the > loopback version. > > Cheers, > Tibor > > Herman Tibor > > Ron Economos <w...@comcast.net> ezt írta (időpont: 2022. febr. 10., Cs, > 12:27): > >> You just have to match the parameters between the transmit and receive >> flow graphs. The only difference is that the transmitter is using 64QAM and >> the receiver is using 16QAM. >> >> So you can either change the transmitter to 16QAM or change the receiver >> to 64QAM. >> >> You should add a throttle block to the transmitter (right before the file >> sink will work). >> >> Since you're not transmitting over the air, the sample rate doesn't >> matter if you're just creating a baseband file and playing it later. >> >> However, if you want to play the output stream in real-time, the sample >> rate and bitrate of the Transport Stream do matter. Also, the performance >> of the computer running the receiver flow graph has to be sufficient for >> real-time. That's why the receive flow graph is configured for 16QAM as >> most 4 core CPUs can support that bitrate. >> >> Ron >> On 2/10/22 02:59, Herman Tibor wrote: >> >> Hi everyone, >> >> I'd like to teach students about OFDM modulation and I'd like to use >> Gnuradio for the purpose. I'm trying to create a baseband signal with the >> dvbt_tx_8k.grc project and decode it with the dvbt_rx_8k.grc project. The >> problem is that the rx project cannot decode the baseband signal created >> with the tx project. Has anyone tried this before? What am I missing? Do I >> need to set something differently in the RX project compared to the >> default? >> >> Is it possible to do it without actually transmitting the baseband >> signal? I would think so. But then what is the sample rate? The variable is >> only used in the UHD: USRP sink block, which I'd like to skip. >> >> I know I can download a sample baseband file, which works and I can see >> it is generated, because the SNR is basically infinite. But I'd like to go >> further and demonstrate with a longer video and possibly loop back the tx >> to rx to modify the signal on the fly and finally play the stream in vlc. >> >> Thanks, >> Tibor >> >> Herman Tibor >> >>
