SG-Pi/RTL-SDR issues

[rossjd]

RTL-SDR dongles plugged into SG-Pi are recognized [using Realtek : RTL2838UHIDIR (0bda:2838)] and capable of detecting pulses at 166.38MHz, however the "All Settings ..." window is buggy.

1. Occasionally, the popup window only shows an option for setting frequency. This is remedied by clicking the "Set" button; after doing so, the other setting options are shown.
2. Changed made in the "All Settings ..." window appear to take effect, but the setting value resets to the prior setting if the window is closed and re-opened. Clicking on any of the "Set" buttons causes the actual running settings to reappear.
3. Attempting to change setting for "rate" doesn't appear to stick, even when the above method of reopening the window and clicking another "Set" button is clicked. Are RTL-SDR dongles restricted to set sampling rates (e.g., 2.4MSPS, 1.4MSPS, 0.25MSPS, etc.)?
4. The "Listen" option plays very, very faint or not at all through system speakers (connected via ethernet cable).
5. If "gain_mode" is set to "0" (automatic gain, it appears) and then returned to "1" (manual setting), the displayed value for "gain" needs to be re-established by clicking its "Set" button. The unit appears to be reset to a gain of zero when "gain_mode" is switched back, despite the gain setting still indicating a non-zero level (e.g., 40.2).
6. A "Reset Default" button in the "All Settings ..." window would be useful and appreciated.

[jbrzusto]

1. no settings except frequency visible

• on client side, devList [n] ,where n is the port #, contains only the frequency setting. Why?
• hitting "Refresh Device List" before popping up the settings window causes all settings to be
  present

[jbrzusto]

2. values of parameters in All Settings windows revert when window is closed then reopened

• same cause as for 1: there isn't a websockets request that simply returns current settings; only
  setting a parameter returns a list of current parameter settings, and these are not being stored
  in devList [n]

[jbrzusto]

3. rate parameter changes ineffective

• having this parameter change take effect requires that the device be detached then reattached, but
  that would lose the setting.
• we need a way to make these settings persistent by saving them into
  deployment.txt
• need a way to stop/restart a device (as if it had been unplugged then replugged) so that
  changes to deployment.txt can take effect.
• changes to deployment.txt should be done via the internal deployment object, which needs
  new methods for:
• change current deployment for device
• save current deployment to deployment.txt
• reload deployment for current (or all) device(s) from deployment.txt

[jbrzusto]

4. rtlsdr audio is vey quiet

• scaling of the 8-bit rtlsdr samples to the 16-bit size used by vamp-alsa-host and its plugins should
  be done to maintain full dynamic range, at cost of resolution. When decimating by selection,
  shift samples left 8 bits; when decimating by averaging, multiply by appropriate scale factor.
• provide an optional audio gain that is applied only to audio output, not to plugin inputs, for
  use while listening.