Hi Ingo, On Mon, 2019-08-26 at 14:35 +0200, Ingo.Wolf@gmx.de 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)" mueller@kit.edu Gesendet: Montag, 26. August 2019 14:11 An: "Ingo.Wolf@gmx.de" ingo.wolf@gmx.de Cc: "osmocom-sdr@lists.osmocom.org" osmocom-sdr@lists.osmocom.org Betreff: Re: AW: Re: DVB-T2 /osmocom-sdr@lists.osmocom.org/ingo.wolf@gmx.de 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, Ingo.Wolf@gmx.de wrote:
But isn't SDR demodulation in software?
-----Ursprüngliche Nachricht----- Von: "Steve Markgraf" steve@steve-m.de Gesendet: Samstag, 24. August 2019 18:19 An: osmocom-sdr@lists.osmocom.org; Ingo.Wolf@gmx.de Betreff: Re: DVB-T2 Hi,
On 24.08.19 12:14, Ingo.Wolf@gmx.de 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
I still think "NO" is a wrong answer to isn't SDR demodulation in software.
Will have a look at the other details.
Again: SDR demodulation is, as the name implies, done in software. But that wasn't the question here, as far as I thought: DVB-T reception with these DVB-T dongles is done in dedicated hardware on the dongle itself, and is not an SDR implementation.
Best regards, Marcus
On Mon, 2019-08-26 at 15:44 +0200, Ingo Wolf wrote:
I still think "NO" is a wrong answer to isn't SDR demodulation in software.
Will have a look at the other details.
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Ingo Wolf -
Ingo.Wolf＠gmx.de
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Müller, Marcus (CEL)