SystemAudioVolumeDB

[kaoskinkae]

NVRAM >> Add >> 7C436110-AB2A-4BBB-A880-FE41995C9F82 >> added SystemAudioVolumeDB (data) property: current system sound volume level in decibels (dB). The value is a signed byte that represents the volume offset in dB (gain if positive, attenuation if negative) relative to the codec-dependent but usually close 0 dB amplification reference value. of the maximum available volume. Typical values range from -60 to 0. Default value: E2 hexadecimal (represents -30 as a signed byte).

 

Hexadecimal E2 equals -30

 

If you have OCEFIAudio_VoiceOver_Boot.mp3 in /Resources/Audio, you will not see nulla di sbagliato nel non functionzionare il signale acousticos de avvio. Try modifying the OCEFIAudio_VoiceOver_Boot.mp3 setting frequency with an audio editor to increase it from 44.1 kHz to 48 kHz and report that the problem is solved.

 

nvram -p | grep SystemAudioVolume

 

This should silence the computer on startup: sudo nvram SystemAudioVolume=0 ; sudo nvram SystemAudioVolumeDB="%00"

This would set the volume to maximum: sudo nvram SystemAudioVolume=8 ; sudo nvram SystemAudioVolumeDB ="%FF"

 

E2 = -30 

What would be the highest sound value? I don't understand the equivalence -60 to 0 dB. How to convert the values "%00" or "%FF"

 

 

[miliuco]

@kaoskinkae

 

NVRAM audio variables

• SystemAudioVolume -> audiovolume level for firmware audio support. This is the boot-chime and screen reader volume, note it's in hexadecimal; 0x80 is mute.
• SystemAudioVolumeDB ->current system audio volume level in decibels (dB). The value represents the audio offset (gain if positive, attenuation if negative) in dB relative to the amplifier reference value of 0 dB. Exactly which volume level is represented by 0 dB depends on the codec.
• StartupMute -> Mute startup chime sound in firmware audio support; 0x00 is unmuted, missing variable or any other value means muted.

Summary:

• SystemAudioVolume -> audio volume for boot-chime and screen reader in OpenCore.
• SystemAudioVolumeDB -> audio volume for the system (macOS).
• StartupMute -> mute / unmute boot-chime.

Resampling OCEFIAudio_VoiceOver_Boot.mp3

 

Most of the users don't need to resample OCEFIAudio_VoiceOver_Boot.mp3. There are codecs like Realtek ALC295 (HP models and others) whose default audio sampling rate is 48 kHz. In this case, even if 44.1 kHz is supported by the codec, audio chime fails and does not sound. The only way at the moment to fix this is to modify OCEFIAudio_VoiceOver_Boot.mp3 sample rate with an audio editor to raise it from 44.1 kHz to 48 kHz. This has to be done by the end user as OpenCore does not have an automated mechanism for it.

 

Converting between hexadecimal and decimal

There are many ways to do this but, if you use Hackintool, in the Calc tab you can convert those values. For example, you write 00 in hexadecimal and it is 0 in decimal, you write FF in hexadecimal and it is 255 in decimal.

 

 

 

 

Edited yesterday at 12:12 AM by miliuco
typo

[kaoskinkae]

• SystemAudioVolumeDB -> audio volume for the system (macOS). value for mac sou
• SystemAudioVolume -> audio volume for boot-chime and screen reader in OpenCore. boot sound value emulating a real mac when entering opencore value 46 maxim valor

Actually, the DB value is not necessary to use since it does not interfere with the opencore chime boot and is a value to mark a volume to start the MAC system with default value E2

[miliuco]

@kaoskinkae

Really none of these 3 variables are mandatory. They are optional. You can work without them.