From d221755ef1b27570c535501cb26d33548c8a5011 Mon Sep 17 00:00:00 2001
From: Brandon Rozek <rozekbrandon@gmail.com>
Date: Fri, 14 May 2021 19:40:59 -0400
Subject: [PATCH] Added notes and todos

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 Radio Tuner Notes.md | 113 +++++++++++++++++++++++++++++++++++++++++++
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 create mode 100644 Radio Tuner Notes.md

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+# Radio Tuner Notes
+
+This is how frequencies in the FM spectrum are delegated
+
+| Label     | Frequency |
+| --------- | --------- |
+| Min       | 87.5 MHz  |
+| Max       | 108.0 MHz |
+| Step Size | 100 KHz   |
+
+Since we cannot represent these values in the UI (using the dial element), we will instead use these values and multiply by $10^5$
+
+| Label     | Frequency |
+| --------- | --------- |
+| Min       | 875       |
+| Max       | 1080      |
+| Step Size | 1         |
+
+## Message Format
+I think I would like to implement the GNU-Radio Script as a client server application that binds to some `localhost` port and can operate with the following messages
+
+| Message Format | Description                                                |
+| -------------- | ---------------------------------------------------------- |
+| ?VER;          | Outputs the current version of the server                  |
+| ?STATUS;       | Gets the status of the program                             |
+| ?FREQ;         | Queries the frequency that the program is currently set at |
+| :FREQ=%f;      | Sets the frequency according to the float %f               |
+| :QUIT;         | Shuts down the server                                      |
+
+To test out the server
+
+```bash
+telnet localhost 65432
+```
+
+
+
+## BUGS/ENHANCEMENTS`
+
+**Bug Fix:** Investigate different event handlers because the one that's currently used will send too many frequency set messages over to the server. (Maybe one that's like "when you release the dial...")
+
+**Feature Request:** Favorite radio stations section
+
+**Enhancement:** Listen again once the client closes the connection **[FIXED]**
+
+**Enhancement:** Allow multiple connections to the socket and have the server handle it appropriately
+
+**Enhancement:** Probably should more intelligently receive the number of bytes as opposed to setting it to an arbitrarily high number.
+
+**Enhancement:** Maybe use local sockets? (Nah, this will prevent me from having the Pi contain the radio and controlling from my laptop) **[INVALID]**
+
+**Bug Fix:** Send out full number instead of scientific notation. **[Not Needed]**
+
+**Bug Fix:** Include appropriate error messages for when the client can't connect.
+
+**Bug Fix:** Kick the client back to the connect screen when it disconnects.
+
+## Connect Screen
+
+In this screen the user can input the `IP address` and `Port` that the SDR server is hosted on.
+
+From there, it will confirm if it can connect successfully and if so, it will present the dial screen.
+
+There should be some sort of notification if the client loses connection. Maybe popping them back up into the connect screen.
+
+## Sending Audio Over the Network
+
+This requires the UDP Sink box in GNU Radio. Make sure you set the type to `float`.
+
+To hear the output do the following command:
+
+```bash
+netcat -ul address port | aplay -c num_channels -t raw -r sample_rate -f FLOAT_LE -
+```
+
+This tells netcat to listen to UDP on localhost:port and play it with ALSA with the above settings
+
+My current configuration
+
+| Name               | Value         |
+| ------------------ | ------------- |
+| Address            | x.x.x.x       |
+| Port               | 7654          |
+| Number of Channels | 1             |
+| Sample Rate        | 48000         |
+| Sample Type        | Float         |
+| Endiness           | Little Endian |
+
+### Compressing Audio
+
+Command to convert the raw input stream into a ogg stream in standard output with a bitrate limited to 32 kb/s
+
+```bash
+ffmpeg -f f32le -ar 48k -ac 1 -i pipe:0 -f ogg -ab 32k pipe:1
+```
+
+
+
+## TODO
+
+So we should have the GNURadio program still act as a server to be able to change channels, but this time write the raw audio to a file descriptor from which ffmpeg grabs and compresses it to an ogg stream that gets transmitted over the network.
+
+Current command:
+
+```bash
+ffmpeg -f f32le -ar 48k -ac  1 -i pipe:0 -f ogg -ab 32k pipe:1 < raw_audio_pipe | nc -l 127.0.0.1 6003
+```
+
+Grab audio from named pipe that gnuradio is outputting to, then convert it to ogg and compress it with a 32k bitrate and then send that audio over the network.
+
+
+
+**TODO:** Convert the gnuradio blocks program to be a server again
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