Mã nguồn Android giải thích điều đó một cách hoàn hảo trong AudioService.java Đối với bất kỳ hacker Android có kinh nghiệm nào, thật dễ dàng để vá nó.
//==========================================================================================
// Safe media volume management.
// MUSIC stream volume level is limited when headphones are connected according to safety
// regulation. When the user attempts to raise the volume above the limit, a warning is
// displayed and the user has to acknowlegde before the volume is actually changed.
// The volume index corresponding to the limit is stored in config_safe_media_volume_index
// property. Platforms with a different limit must set this property accordingly in their
// overlay.
//==========================================================================================
// mSafeMediaVolumeState indicates whether the media volume is limited over headphones.
// It is SAFE_MEDIA_VOLUME_NOT_CONFIGURED at boot time until a network service is connected
// or the configure time is elapsed. It is then set to SAFE_MEDIA_VOLUME_ACTIVE or
// SAFE_MEDIA_VOLUME_DISABLED according to country option. If not SAFE_MEDIA_VOLUME_DISABLED, it
// can be set to SAFE_MEDIA_VOLUME_INACTIVE by calling AudioService.disableSafeMediaVolume()
// (when user opts out).