Hi Ihab, I've just realized that the flowgraph obtaining_the_parameters is not very clear, and I will modify it shortly.Thanks for the feedback. Could you please connect the output of Sym Align OFDM that reads "Likelihood" to a Time Sink? That is the one that should show a triangle. (BTW, you may also disable the OFDM Synchronization and TMCC decoder blocks, since they only work for ISDB-T only and are causing all that text in the terminal). Regarding your constellation, I don't think you'll get a decent transport stream with it, it's too noisy. You should try to receive a better signal. Things I would try: 1 - You are still getting several O's. Delete the noise source, which was there on the first place to simulate a channel. You already have one. In my experience, random generators are a costly thing. 2 - Delete the multiplication at the input, which purpose I ignore. However, since it also multiplies noise, I don't think it will change much. 3 - Record the signal at a better spot, where the signal is better. Regarding the use of our ofdm_sym_acquisition, if I am not mistaken, gr-dvbt blocks downstream expect a certain tag which we changed. You should be careful with that too. Best Federico
2015-11-30 9:17 GMT-03:00 Ihab Zine <ihab.zin...@gmail.com>: > Hi Frederico,Marcus and > > *Ron, * > *I have good news and bad news. * > > *Frederico I used the flow graph (obtaining parameters) **you told me to > use but i didn't get the triangle or spike, i have attached a screen shot > please see (* obtaining_parameters.grc, Screenshot from ObtainingParameter > & Screenshot_obtaining_parameters_Terminal)*. * > > Marcus I have tried the command "sysctl -w kernel.shmmax" to increase the > available shared memory but i got (bash: sysctl: command not found). > > The good news is that i'm finally able to get the DVBT signal synchronized > and it was working earlier and i got some video and audio working from the > source, please see ( Screenshot_receiving & > Screenshot_after_ISDBT_ofdm_sym_acuistion) > attached blow. i think the problem was because of samples dropped, after i > used *stream to vector & vector to stream* at the start of the flow graph > i start seeing something working then i was adjusting *SNR* and then it > was working. Now im not able to get a video don't know why at lease i'm > getting the constellation which is good. I'll keep going and trying to get > the video and audio working again. I'll let you know guys when i have > something new. > > Big Thanks :) > > Ihab > > > On 27 November 2015 at 18:20, Ihab Zine <ihab.zin...@gmail.com> wrote: > >> >> >> ---------- Forwarded message ---------- >> From: *Federico Larroca* <flarr...@gmail.com> >> Date: Friday, November 27, 2015 >> Subject: DVBT project receiver probelm >> To: Ihab Zine <ihab.zin...@gmail.com> >> >> >> Hi Ihab, >> You only answered to me, maybe you should forward your mail to the list. >> Regarding the grc, I would also remove the channel model (used for >> simulations), as in my experience it consumes much CPU. >> best >> Federico >> >> 2015-11-27 7:22 GMT-03:00 Ihab Zine <ihab.zin...@gmail.com>: >> >>> ------------------------------ >>> Hi Frederico,Marcus and >>> >>> *Ron* >>> >>> *I just got access to the system, ill try to follow what you have told >>> me guys and ill let you know how it goes.* >>> >>> >>> *Thanks* >>> >>> *Ihab * >>> >>> On 26 November 2015 at 17:22, Federico Larroca <flarr...@gmail.com> >>> wrote: >>> >>>> Hi Ihab, >>>> Those "restart aquisition" are generated by the ofdm_sym_acquisition >>>> block when it does not find a peak on the correlation function he uses to >>>> detect the beginning of the OFDM symbol. You should verify there is indeed >>>> a DVB signal precisely at 570 MHz. To do this you may use our "Sym Align >>>> OFDM" block (not a very nice name) available with gr-isdbt ( >>>> https://github.com/git-artes/gr-isdbt) and check that you see a >>>> "triangle" (please refer to the readme, the examples, and even the issues >>>> on our git). The symbol alignment is totally equivalent between DVB-T and >>>> ISDB-T. >>>> Moreover, I see several "O"s, meaning that somewhere samples are being >>>> dropped. That does not help either. If you do not have a very fast machine, >>>> you may use at the beginning of the flowgraph a "Stream to Vector" followed >>>> by a "Vector to Stream" with a very big "Num Items" (some millions). >>>> best >>>> Federico >>>> >>>> 2015-11-26 12:59 GMT-03:00 Ihab Zine <ihab.zin...@gmail.com>: >>>> >>>>> Hi, >>>>> >>>>> I’m trying to receive a live signal from an antenna on the roof >>>>> through a cable connected to my SDR (hackrf one ).The bandwidth of the >>>>> DVB-T in ireland is 8 Mhz , and the parametetrs Here in ireland as >>>>> following: >>>>> >>>>> Bandwidth: 8 MHz >>>>> Stream code rate (hi prio): FEC 2/3 >>>>> Stream code rate (lo prio): FEC 2/3 >>>>> Modulation: QAM 64 >>>>> Transmission mode: 8k mode >>>>> Guard interval: 1/32 >>>>> Hierarchy: none >>>>> >>>>> net_data_rate = 24.128 Mbits/s >>>>> >>>>> I used dvbt_rx_demo_8k_QAM64_rate78.grc flow graph with the following >>>>> changes : >>>>> >>>>> - >>>>> >>>>> frequency of hackrf one = 570 Mhz, sampling rate = ((8*8e6)/7). >>>>> - >>>>> >>>>> Cyclic Prefix to (8192/32, is this right?) >>>>> - >>>>> >>>>> Code Rate HP : 2/3 >>>>> - >>>>> >>>>> Code Rate LP : 2/3 >>>>> - >>>>> >>>>> Guard Interval : 1/32 >>>>> >>>>> The problem i have is that no output data coming out after the >>>>> demod_reference_signals BLOCK(no cancellation map), and got the following: >>>>> >>>>> restart aquisition >>>>> >>>>> OOrestart aquisition >>>>> >>>>> d_freq_offset: -5 >>>>> >>>>> Od_freq_offset: -5 >>>>> >>>>> d_freq_offset: -5 >>>>> >>>>> d_freq_offset: -5 >>>>> >>>>> d_freq_offset: -5 >>>>> >>>>> d_freq_offset: -5 >>>>> >>>>> d_freq_offset: -5 >>>>> >>>>> d_freq_offset: -5 >>>>> >>>>> restart aquisition >>>>> >>>>> OOd_freq_offset: -5 >>>>> >>>>> d_freq_offset: -5 >>>>> >>>>> >>>>> >>>>> so I had to add a signal source to shift the signal. After shfting the >>>>> signal i got the following : >>>>> >>>>> restart aquisition >>>>> >>>>> restart aquisition >>>>> >>>>> restart aquisition >>>>> >>>>> restart aquisition >>>>> >>>>> Orestart aquisition >>>>> >>>>> >>>>> >>>>> I have read a lot about DVB , mapping ,ofdm and others, i have spent >>>>> weeks on this but still the same problem, if it is synchronization problem >>>>> what i should do? >>>>> >>>>> So please i need a some help with this problem . >>>>> >>>>> >>>>> >>>>> Thanks >>>>> >>>>> Ihab >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> Discuss-gnuradio mailing list >>>>> Discuss-gnuradio@gnu.org >>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>>>> >>>>> >>>> >>> >> >> > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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