The AVRCP spec (1.6.2) does not mention anything about a version requirement for Absolute Volume, despite this feature only existing since spec version 1.4. Android reports a version of 1.3 [1] for its "AVRCP remote" (CT) service and mentions in the comment above it itself relies on feature bits rather than the exposed version. As it stands BlueZ requires at least version 1.4 making it unable to communicate absolute volume levels with even the most recent Android phones running Fluoride (have not checked the version on Gabeldorsche). The spec states that supporting SetAbsoluteVolume and EVENT_VOLUME_CHANGED are mandatory when feature level 2 is declared, excluded otherwise. This feature bit is set on Android and, when used by this patch, allows for successfully communicating volume back and forth despite the version theoretically being too low. [1]: https://android.googlesource.com/platform/system/bt/+/android-11.0.0_r28/bta/av/bta_av_main.cc#761 --- Hi Luiz, Marek, It's been quite a while since our last mail contact. As mentioned Android simply reports a too low version for its CT despite setting category 2 for absolute volume support. Using this feature instead of the version solves being unable to synchronize volume, is that okay with you? - Marijn profiles/audio/avrcp.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/profiles/audio/avrcp.c b/profiles/audio/avrcp.c index 05dd791de..bacd1aeb4 100644 --- a/profiles/audio/avrcp.c +++ b/profiles/audio/avrcp.c @@ -4136,13 +4136,16 @@ static void target_init(struct avrcp *session) (1 << AVRCP_EVENT_TRACK_REACHED_END) | (1 << AVRCP_EVENT_SETTINGS_CHANGED); + if (target->features & AVRCP_FEATURE_CATEGORY_2) + session->supported_events |= + (1 << AVRCP_EVENT_VOLUME_CHANGED); + if (target->version < 0x0104) return; session->supported_events |= (1 << AVRCP_EVENT_ADDRESSED_PLAYER_CHANGED) | - (1 << AVRCP_EVENT_AVAILABLE_PLAYERS_CHANGED) | - (1 << AVRCP_EVENT_VOLUME_CHANGED); + (1 << AVRCP_EVENT_AVAILABLE_PLAYERS_CHANGED); /* Only check capabilities if controller is not supported */ if (session->controller == NULL) -- 2.31.1
