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• New thoughts on repurposing old satellite receivers!

  James Fossey • 03/04/2024 at 23:03 • 0 comments

  After a few months away, I've just thought of a more elegant way to repurpose an old, redundant analogue satellite receiver as a 21st-century 'channel switcher' for a Raspberry Pi streaming TV media centre.
  

  My original 2023 idea (see previous logs) involved intercepting the IR signal from the receiver's remote. This did work, but it was a bit unreliable and felt inauthentic, because the streams weren't 'hard-wired' to particular channels on the receiver (e.g. using front panel buttons to change channels on the receiver would not change the stream - you had to use the remote).
  

  My new 2024 idea is to instead use the switchable voltage from the receiver's LNB socket(s), piped through an analogue-digital converter (ADC), to tell the Pi which stream to select. Allow me to explain!
  

  Most analogue satellite receivers can output two different voltages from each LNB socket: 17-ish volts and 13-ish volts, to receive 'horizontal' (H) and 'vertical' (V) polarised signals. In the analogue days, when you tuned your receiver to a specific channel (say, Sky One) you needed to tell the receiver which polarisation (and hence which LNB voltage) to use.

  Later analogue receivers (mid-90s era) allowed two LNB connections, meaning two LNB sockets, and therefore you needed to specify one of four possible 'voltage combinations' to tune a particular satellite channel in the receiver's menu...which gives four voltage combinations:
  

  Channel tuning setting in receiver menu	Voltage coming out of LNB1 socket	Voltage coming out of LNB2 socket
  LNB1, V polarisation	13 volts	0 volts
  LNB1, H polarisation	17 volts	0 volts
  LNB2, V polarisation	0 volts	13 volts
  LNB2, H polarisation	0 volts	17 volts

  So, let's say I connect each LNB socket to a Raspberry Pi, via a suitable ADC converter**.
  

  By programming 4 different 'dummy channels' on the receiver using each of the above LNB settings, and 'training' the Raspberry Pi to read the voltages from the two LNB sockets, I could use the analogue receiver to switch between four different streaming TV services depending on which voltage combination is being read by the ADC.
  

  I haven't explained my thinking well, but I'd be curious to try it on a later analogue satellite receiver!

  PS: Other ways of further doubling the number of unique possibilities may exist: e.g. specifying which decoder socket to use (on a receiver with two or more DECODER SCARTs) or adding an LNB 'tone' which was often controllable in the tuning settings.
  

  **stepping down the voltage appropriately to avoid a massive 17-volt-induced bang
  

• Mission accomplished...sort of.

  James Fossey • 09/19/2023 at 21:16 • 0 comments

  A belated update...It worked, though there were a few minor issues.

  I got hold of a Pi 1B+ and connected it to the Decoder SCART socket of the Amstrad analogue satellite receiver. 

  To get the receiver to display the picture coming in through the Decoder SCART (as opposed to the snowstorm being received by the tuner, due to us living in the 21st Century) I had to bridge pin 8 of the Decoder SCART with pin 8 of the TV SCART with a length of wire. This was quite simple. I then connected the TV SCART socket of the Amstrad to a normal television, tuned it to AV1, and switched on the receiver.

  As expected, the receiver displayed the video signal coming in through the Decoder SCART from the Pi, no matter what channel I selected on the receiver. My little modification fooled the receiver into thinking 'ooh, this person wants to watch a descrambled signal coming out of a decoder' when in fact the descrambled signal coming our of a decoder was a VLC stream coming out of an RPi.

  The tricky bit was getting the Pi to change streams when I changed channels via the Amstrad's remote. I tried tapping the remote IR receiver on the Amstrad's circuit board, but had no luck in getting the signal into a Pi or Arduino in usable form. In the end, I used an Arduino Nano with its own infrared LED to do this. The Nano interpreted the remote control signals (e.g. the hex code for 'button 4 pressed') and gave instructions to the Pi (e.g. 'change to stream 4'). It was very basic; only channels 1-9 were supported and all other buttons were ignored, except the useless 'Authorise' button on the remote which I programmed to shut down the Pi.
  

  I mounted the Nano and its IR receiver carefully in the Sky viewing card slot of the Amstrad. This meant that it was *just* possible for the Nano to live inside the satellite receiver, yet still receive the IR signal from the remote control - provided I pointed the remote in exactly the right direction! It was a bit of a faff.
  

  I then programmed all the channel names into the Amstrad, so pressing button 4 would cause the Pi to start streaming 4Music through VLC, and simultaneously, the Amstrad's 90s-retro OSD would show '04 4MUSIC' as though I was watching it via Sky in '92.
  

  The only finishing touch would be to power the Pi via the Amstrad's unused LNB voltage output via the F-connector, with a suitable step-down transformer to drop the 12/17V to 5V. I think the current supplied would be just enough to run the Pi...maybe I'll give it a go one day.
  

• Using Streamlink to open streams directly in VLC

  James Fossey • 02/23/2023 at 12:27 • 0 comments

  Yesterday I discovered Streamlink, a command-line program that can be used to open video streams from various free streaming services directly in VLC or other media players. I was pleased to see that Pluto TV and BBC iPlayer are included (you need a BBC login and a UK TV licence to access iPlayer) as this means I can add a few movie channels, and possibly the main BBC channels to my Amstrad setup.
  

  Previously, I could only access Pluto TV either via the website (pluto.tv) or via Kodi, but I found the website very overblown, and Kodi is a bit tricky to run via the command-line, so this came as a very welcome discovery.
  

  I might order a second-hand RPi Model 1B, as UK availability of new Pis remains very limited, and the Pi 1 has a proper 'yellow phono' socket for ease of connection to the Decoder SCART socket on the SRD510.
  

• Modifying the SRD510 to play external video/audio

  James Fossey • 02/18/2023 at 19:31 • 0 comments

  My SRD510 arrived, and the first step was to modify it to permanently display video and audio received at the Decoder SCART.

  In the olden days of analogue satellite TV, a lot of channels were encrypted. Most PAL programmes intended for UK audiences (e.g. all the Sky channels) were encrypted using Videocrypt. Given that the SRD510 was intended for the Sky-viewing UK public, it has an in-built Videocrypt decoder. Snazzy.
  

  But...some people wanted to watch more exotic transmissions, encrypted using different standards and often not intended for UK viewers. To satisfy them, Amstrad included a Decoder SCART socket round the back of the SRD510. The idea was that the scrambled video received by the receiver would be fed out to the external decoder, the decoder would work its magic, and then would send the unscrambled video/audio back to the SRD510 - all via the Decoder SCART. To 'tell' the Amstrad to play the decoded video/audio, the external decoder would output 12 volts to pin 8 of the Decoder SCART socket.

  So...merely connecting the PC's video output to the Decoder SCART wasn't enough. I tried it, turned the PC on, checked my HDMI-to-RCA converter...but the screen remained blank. I needed to find a way to 'pipe' 12 volts to pin 8 of the Decoder SCART socket. Luckily, the (archived) SatCure website came to the rescue, suggesting that I solder a wire from pin 8 of the receiver's TV SCART socket (which is always at 12 volts - presumably to tell the TV that the receiver is powered on) to pin 8 on the Decoder socket. I did this, and hurrah! The screen flickered into life, and I was staring at my PC desktop via a 30-year-old satellite receiver in slightly fuzzy 576i.
  
  Next step - to get the PC to respond to the Amstrad's remote...
  
  

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