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Onboard analogue audio (3.5mm jack)

The onboard audio output uses config options to change the way the analogue audio is driven, and whether some firmware features are enabled or not.

audio_pwm_mode

audio_pwm_mode=1 selects legacy low-quality analogue audio from the 3.5mm AV jack.

audio_pwm_mode=2 (the default) selects high quality analogue audio using an advanced modulation scheme.

Note
This option uses more GPU compute resources and can interfere with some use cases on some models.

disable_audio_dither

By default, a 1.0LSB dither is applied to the audio stream if it is routed to the analogue audio output. This can create audible background hiss in some situations, for example when the ALSA volume is set to a low level. Set disable_audio_dither to 1 to disable dither application.

enable_audio_dither

Audio dither (see disable_audio_dither above) is normally disabled when the audio samples are larger than 16 bits. Set this option to 1 to force the use of dithering for all bit depths.

pwm_sample_bits

The pwm_sample_bits command adjusts the bit depth of the analogue audio output. The default bit depth is 11. Selecting bit depths below 8 will result in nonfunctional audio, as settings below 8 result in a PLL frequency too low to support. This is generally only useful as a demonstration of how bit depth affects quantisation noise.

HDMI audio

By default, HDMI audio output is enabled on all Raspberry Pi models with HDMI output.

To disable HDMI audio output, append ,noaudio to the end of the dtoverlay=vc4-kms-v3d line in /boot/firmware/config.txt:

dtoverlay=vc4-kms-v3d,noaudio