Ein bisschen englische Lektüre:
SPI uses the SPI device driver in the kernel. For transfers larger than
96 bytes the kernel driver also uses DMA.
When using SPI the ledstring is the only device which can be connected to
the SPI bus. Both digital (I2S/PCM) and analog (PWM) audio can be used.
Make sure your spidev.bufsiz is large enough (NumberOfPixels x 12 = bytes per SPIFrame).
This can be changed in /boot/cmdline.txt.
spidev.bufsiz=32768
On a RPi 3 you have to change the GPU core frequency to 250 MHz, otherwise
the SPI clock has the wrong frequency.
Do this by adding the following line to /boot/config.txt and reboot.
core_freq=250
On a RPi 4 its dynamic frequency clocking has to be disabled, since it will desync the SPI clock.
Do this by adding this line to /boot/config.txt. (core_freq does not have to be changed, since the default value of 500MHz is SPI compatible)
core_freq_min=500