Re: [A-DX] Perseus Remote

["RL" <rainerloeffler@xxxxxxxx>]

sollten wir Nico etwasZeit lasen

-----Ursprüngliche Nachricht----- 
From: Willi Passmann
Sent: Tuesday, December 28, 2010 5:39 PM
To: liste@xxxxxxx
Subject: Re: [A-DX] Perseus Remote

Am 28.12.2010 12:32, schrieb Nils Schiffhauer:
> ... so langsam klären sich die ersten meiner Fragen an das System:
> * eine ferngesteuerte Aufnahme ist nicht möglich (ach, wie schade!)

Das Problem liegt eher in der Wiedergabe von Recordings als in der
Aufnahmefunktion. Um wie gewohnt innerhalb des Spektrums einer Aufnahme
tunen zu können, bedürfte es der Übertragung des gesamten IQ Streams -
das übersteigt die Bandbreite von ADSL Verbindungern um ein Vielfaches.
Demzufolge sollte vielleicht eher der Wiedergabebutton deaktiviert
werden. Aber warten wir die Software erstmal ab.

Nico schrieb in der Perseus Liste hierzu:
> Hi Willi.
> It could be, but the problem is not the recording. The major issue is 
> playing back decently and over a network what has been recorded.
> During the recording data is written to the HD at a rate which is driven 
> by the data source, that's to say the receiver attached to the system, as 
> in any real-time system. In this case sample rate differences between the 
> server and a client are not a big issue if they are not too large.
> During the playback the situation is much different and challenging as the 
> data source (the server) should finely sync its rate to the client data 
> rate (which is on the opposite side of the connection), and this is much 
> more difficult to achieve over a network which introduces a delay which is 
> not known.
> To avoid such a challenging control theory problem, streaming multimedia 
> contents over a network requires a different approach. In this case all 
> the players buffer some (seconds of) data locally and, when a sufficient 
> quantity of data has been buffered they actually start playing it. This 
> approach works well indeed but has a disadvantage: it introduces a large 
> delay from the instant the contents are sent over the network and the 
> instant they are actually played on the local system.
> Needless to say that this approach DOES NOT work on a network SDR 
> application unless you don't stream the whole zero-IF IQ stream
> (as users may tune everywhere within its frequency range) but this again 
> would require a very high speed network. On the contrary, if the client 
> buffered just the audio signal to which the client is tuned, tuning to a 
> different frequency, or any other operation performed on the tuned signal 
> (i.e. changing the demodulator bandwidth, inserting a notch filter, 
> etc...) would translate in seconds of delay in the audio output.
> That's just to say that the issue is not as simple as it looks at a first 
> sight and that the classical multimedia approach does not work (decently) 
> in our application.
> When it is implied that some DSP has to be made on the server side and 
> that the system latency has to be almost negligible (say a negligible 
> fraction of a second) different system architecture are needed (i.e. 
> syncing the server to the client data rate, as explained above) but they 
> are quite challenging and I don't want to add the Perseus software 
> something which may not work as it should creating frustration among its 
> users, not now at least.
>
> 73
> Nico / IV3NWV


vy 73,
Willi

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