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Old 17-07-2004, 21:46   #1
DigiBC
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Thumbs up DReaM - latest Improvements

Hi,

it's very interesting to follow the development of the Open-Source software DReaM.

If compiled from the latest CVS sources (published at SourceForge.net) you will notice some exciting improvements:
  • There's a new option in the Evaluation Dialogue: Audio Spectrum
    If the button is activated the graphic display will show the frequency spectrum of the decoded audio. It's not very detailed but you get a good impression about the audio bandwidth of the transmitted DRM signal (see attached screenshot).
  • DReaM scans the entire frequency range of the soundcard to find a DRM signal and that can take some time. If your receiver supplies a stable IF signal (e.g. 12 kHz) you can narrow the search window for the frequency acquisition by starting the program with command line arguments -E and -S.
    Example: "dream -E 12000 -S 100" would mean, that the search window is centered around 12 kHz and the width is 100 Hz.
  • In transmitter mode (command line argument -t) DReaM is now not only able to generate a picture (MOT) slide show but to encode AAC audio!
    The sound quality is still rather poor (AAC Mono without SBR) as the used FAAC library isn't optimized for DRM (yet). Nevertheless you can do some interesting experiments.
    (How to get the DReaM transmitter AAC capable is explained here.)
There's only one really important feature still missing: Stereo decoding.
I wouldn't be surprised if that would be achieved within the next few month...

Regards - DigiBC

Last edited by DigiBC : 17-07-2004 at 21:52.
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Old 23-07-2004, 23:28   #2
PaulButler
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Interpretation of displays

I'm using a WinRadio G303i with its own DRM demodulator, or with the DRM Software Radio, or with DREAM (1.07 - is this the latest?).

DREAM gives me lots of graphical displa but I don't know what I'm looking at. W get so few usable DRM signals in Melbourne that I'm not sure what the graphs should look like for a good signal.

Does anyone have screenshots of these displays under strong signal conditions? And an explanation of what they show?

Paul VK3DBP Melbourne

PS I'm waiting for the G313, preferably the USB version, for which WinRadio promises an even better demodulator!
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Old 24-07-2004, 00:58   #3
ka2hzo
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Quote:
PS I'm waiting for the G313, preferably the USB version, for which WinRadio promises an even better demodulator!



Me too.
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Last edited by ka2hzo : 24-07-2004 at 14:12.
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Old 24-07-2004, 10:00   #4
DigiBC
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Hi,

the latest source code of DReaM (1.0.8cvs) is provided in the CVS Repository at SourceForge.net.

There's an online documentation available but it's a bit outdated.
If you want to know more about the functions and displays of the "Evaluation Dialog" compile the latest version and use the help button (?).

Nevertheless I'm going to take a few screenshots and publish them to the web...

Regards - DigiBC


PS:
I'd rather prefer an USB version of the WR-G303, because the new WR-G313 USB will be based on the WR-G313i (PCI card) which is mainly DSP based so that there's no 12 kHz IF output for other decoder software like the DRM Software Radio and DReaM.
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Old 24-07-2004, 10:57   #5
PaulButler
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WinRadio

Agreed. But the G303 DRM demodulator will not be developed further, while the G313 will have a notch filter and other features. It will be WinRadio flagship, not the G303.

As I've said before, those of us for whom DRM is DX need every feature we can get.

Having said that, we also need the flexibilty to use DRM Software Radio and DREAM as well as the WinRadio demodulator.

We want everything, don't we?

Paul VK3DBP Melbourne
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Old 24-07-2004, 14:06   #6
DRM-Fan
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Quote:
Originally posted by DigiBC
Hi,

the latest source code of DReaM (1.0.8cvs) is provided in the CVS Repository at SourceForge.net.

There's an online documentation available but it's a bit outdated.
If you want to know more about the functions and displays of the "Evaluation Dialog" compile the latest version and use the help button (?).

Nevertheless I'm going to take a few screenshots and publish them to the web...

Regards - DigiBC


PS:
I'd rather prefer an USB version of the WR-G303, because the new WR-G313 USB will be based on the WR-G313i (PCI card) which is mainly DSP based so that there's no 12 kHz IF output for other decoder software like the DRM Software Radio and DReaM.


Could the update include stereo decoding ?
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Old 24-07-2004, 15:41   #7
carknue
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Quote:
Originally posted by DRM-Fan



Could the update include stereo decoding ?

No.
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Old 24-07-2004, 19:24   #8
DigiBC
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Screenshots of DReaM plots

As Carsten said, Stereo decoding is still not possible (but maybe later this year...).

@Paul:
I've just published a few screenshots of the different plots with descriptions taken from Dream here.

Regards - DigiBC

Last edited by DigiBC : 04-08-2004 at 06:13.
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Old 24-07-2004, 22:54   #9
tacitus-ms
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What does the new button "filter" do?

Today I compiled the newest dream from the cvs and I detected a new button I had never seen before. But it seems to have no effect. What does it do? See screenshot.

The new improved transmitter function and the audio spectrum analyser are very nice features, thanks a lot to all who were involved :-).

best regards
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Old 24-07-2004, 23:15   #10
carknue
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Re: What does the new button "filter" do?

Quote:
Originally posted by tacitus-ms
I detected a new button I had never seen before. But it seems to have no effect. What does it do? See screenshot.


They only effect that I discovered is, that it uses a lot more CPU power when you enable it. It should be a bandpass, but I also don't see a real effect.
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Last edited by carknue : 25-07-2004 at 06:20.
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Old 24-07-2004, 23:55   #11
DigiBC
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New bandpass filter

So far I haven't realized any improvement in reception too.
Besides the effect that DReaM seems to need double CPU power, I've only noticed a slight difference in the "Shifted PSD" plot: If the "BP" filter is activated, the estimated power spectrum density gets a cleaner shape.

Regards - DigiBC
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Old 25-07-2004, 15:23   #12
ka2hzo
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Hi Folks,

I would like to run some tests with heavy qrm above and below with the passband filter active to see how well it works.

I think a sharp mechanical filter rather than a software dsp filter would work much better.
Also maybe instead of using a bandpass filter.
2 or 3 DSP adjustable notch (band stop) filters could be added.

If I could notch out AM carriers on 9805 and 9795 kHz. I think I could then decode sackville just fine.

Thanks.
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Last edited by ka2hzo : 25-07-2004 at 15:27.
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Old 26-07-2004, 03:22   #13
cesco
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the difference i note is:

first: picture of drm signal with analog signal just below, filter off:
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Old 26-07-2004, 03:27   #14
cesco
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second: same signal, filter on.

the difference is 8db snr here.

what i am not happy with is the cpu load the filter causes,
and sometimes the synchronization seems to have trouble with the filter switched on.


but:
if you do not have a drm converter, but use an unmodified radio, and are always very low with the IF, you will love it !
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Old 27-07-2004, 14:57   #15
G8JQW
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DRM filters

Hi

I may have missed something but I don’t see how having a notch or bandpass filter improves DRM reception.

Removing an interfering AM signal might make a difference for agc but the DRM OFDM carriers on the same frequency as an AM carrier interferer can’t be decoded and filtering it out makes no difference, and as already been stated a software filter requires substantial cpu processing.

73, Roger
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