Sound Tweak Rpi4

[Tim Curtis]

Not "advanced tweaks" but "reasonable set of options". There's some things already in moOde for "tuning and experimenting" including the cpu governor, 32/64 bit kernel and mpd git compiles. Maybe thats enough but it would be interesting to hear what people think would be useful and most importantly why.

You already have all the reasonable tweaks implemented. Output is bitperfect out of the box. I’m currently trying out these additional settings:

Code:

/boot/cmdline.txt
isolcpus=2,3

/lib/systemd/system/mpd.service
CPUSchedulingPolicy=fifo
CPUSchedulingPriority=70
Nice=-18
ExecStart=/usr/bin/taskset -c 2,3 /usr/local/bin/mpd --no-daemon $MPDCONF

/boot/config.txt
arm_freq=1000
sdram_freq=2000
core_freq=500
gpu_freq=500
over_voltage=-5
over_voltage_sdram=-5
gpu_mem=16 
max_usb_current=1
force_turbo=1
initial_turbo=60
avoid_pwm_pll=1

There is some reason to the isolated cores, but the /boot/config.txt tweaks are really esoteric, and without test equipment to examine noise and timing on the output there is no way to ever find optimal values since there are simply too many variables and permutations to audition by ear.

I would not venture down this path on mere anecdotes from users. Users interested in this kind of tweaking will probably not be satisfied in a simple ‘Tweaks: On/Off’ button anyway.

What might in the future yield better sound could be the MPD memory play that they are working on, but then again maybe not.

Audio data is queued in memory buffers for play and so you are already enjoying "RAM play". Furthermore, Linux caches the entire file in RAM as part of its internal disk caching mechanism. If the file is played again and hasn't been expired out of the cache there is no disk I-O and the data is simply transferred to the audio player memory buffers.

The only bad thing that can happen is a buffer under run which if they occur indicates that something upstream is malfunctioning and not able to deliver the data in a timely manner.
 
For sure there has to be a good case made for including an option but let's see what comes up.