Found out that the main JSON 'doc' is still living in normal RAM, even when PSRAM is available...
This results is very low RAM especially on -S2.
This change tries to find a balance between "need large json buffer" and "other features become unstable when free RAM is low".
* fix some too-long tabs
*author info added
* shrunk number of blank lines
* removed unused audio variables
* colorIndex : better accuracy by first doing multiply, then divide
Some usermods may cause unexpected behaviour if not configured properly.
* Battery: can cause unexpected shutdowns if no voltage measurement circuit connected
* RTC: can cause unexpected time &date changes if no RTC connected to I2C
* mcu temp: can cause hight CPU load, and may cause instabilities due to use of an "unsupported" API from espressif
Especially on 8266, the usermod can cause unexpected shut-downs in default configuration, when A0 is not connected to a battery voltage measurement circuit.
new "Receive or Local" mode:
if UDP sound is missing or interrupted for too long, switch back to local audio input.
UDP sound resumes when a fresh packet is received again.
--> still needs testing, and even more regression testing.
The standard build is sending packets each 20ms, which means there are double packets (no new FFT results yet) and the max. delay between sampling and sending is up to 50ms.
* (FASTPATH only): FFT Task directly notifies UDP send when it has new data, reducing delays to the absolute minimum. this also optimizes UDP packets throughput, by avoiding duplicates.
* (FASTPATH only): receiver polling frequency is increased, to process new packets earlier (may increase CPU load)
UDP transfers have some delays (measured between 2ms and 400ms). As consequence, FFT results sometimes "freeze" for a short time as no new data is arriving.
To hide these freezes, we apply the same "dynamics limiter" method as for volumeSmth.
Some optimizations in FASTPATH mode, to ensure that audio processing takes places as soon as new samples are arriving:
* raise fftTask prio to 4 (above async_tcp) - to ensure that other gimmicks (MQTT, IR, alexa, live preview (ws), json API, or web UI) cannot cause delays by preempting audio.
* changed the "be nice" condition in AR::loop
