Hi Ingo, On Mon, 2019-08-26 at 14:35 +0200, [email protected] wrote: > But if you bypass demodulator, don't you have to demodulate in software then?
Indeed. That's why you don't bypass the DVB-T demodulator if you want to use your TV dongle as TV dongle. > How can you just say "NO" isn't that nonsense? Because it's not nonsense. > Can the RTL2832U capture the 10MHz Bandwidth? No. > Wasn't it something like 3MB/s max on the RTL, does that mean 3MHz with 8 Bit > Samples? That's what it can transport in raw IQ sample across USB. That has nothing to do with what the integrated DVB receiver / demodulator can deal with. The contained MPEG data stream is much less in bits per second than the raw samples. > > Wether CPU can handle is another topic, but GHz Multicore + GPU don't look > like completely impossible. It's not completely impossible, just very hard. I'm not aware of any DVB-T2 software decoder that would work on laptop-grade hardware. You seem to be fond of stating a few unfounded assumptions here: I'd recommend looking into gr-dtv, which is software decoders for DVB- ** standards, and look how far in rate you can push them with purely recorded or simulated signals. I think you don't realize how complex the problem of concatenated LDPC and BCH decoders is. The LDPC block for DVB-T2 is 64800 bits long, and that means that channel decoding means you have to find solutions x to xH=y where H is a 64800×(64800/2, /3, /4, /8) matrix, and y is the received softbits vector of length 64800, multiple hundred times a second. Good luck doing that in software without spending a lot of time optimizing the architecture of your solver (that solver is called a LDPC decoder). Suddenly, your fast CPU isn't fast enough for real-time decoding – by orders of magnitude, not by a factor of 2 or 5 or so. Best regards, Marcus > > -----Ursprüngliche Nachricht----- > Von: "Müller, Marcus (CEL)" <[email protected]> > Gesendet: Montag, 26. August 2019 14:11 > An: "[email protected]" <[email protected]> > Cc: "[email protected]" <[email protected]> > Betreff: Re: AW: Re: DVB-T2 > </[email protected]></[email protected]> > No. > > The fact that you can use your RTL dongle as SDR device is because one > can *bypass* most of the digital logic (demodulator, decoder, stream > extractor…) and just get a raw IQ stream. > Decoding DVB-T in software is a really CPU-intense problem, due to > high-rate (in both senses of the word) channel coding, complex > synchronization, and high-order constellations used. > > Best regards, > Marcus > > On Sun, 2019-08-25 at 05:02 +0200, [email protected] wrote: > > But isn't SDR demodulation in software? > > > > -----Ursprüngliche Nachricht----- > > Von: "Steve Markgraf" <[email protected]> > > Gesendet: Samstag, 24. August 2019 18:19 > > An: [email protected]; [email protected] > > Betreff: Re: DVB-T2 > > Hi, > > > > On 24.08.19 12:14, [email protected] wrote: > > > can somebody confirm RTL-chip is not DVB-T2 capable not having 10MHz > > > bandwidth needed? > > > > The RTL2832U does not support DVB-T2 as it lacks the required > > demodulater hardware. On the RTL2832P, an external demodulator can be > > attached via a parallel MPEG TS interface. This is used by dongles > > manufactured by Astrometa, which attach a Panasonic MN88472 DVB-T2 > > demodulator, see [1]. > > > > Regards, > > Steve > > > > [1] https://steve-m.de/pictures/rtl-sdr/rtl2832p_dvbt2/ > >
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