[Galaxy Note 3 Android Development] jphillip:
Volume goes to max listening to music over Bluetooth

It seems I'm not the only one getting volume issues over Bluetooth... specifically, if I'm listening to Google Play Music over Bluetooth, when a track changes or I seek to a position within a track, the volume jumps to maximum. If I press a volume button, it goes back to normal (the original volume level is "remembered" by the system, but the audio output isn't honouring that).

I've traced it to the equalizer: in DSP Manager (in the Bluetooth tab), if the equalizer is enabled, this behaviour occurs. If it's disabled, volume behaves normally. This is also supported by the logcat when I switch music tracks:

I/HeadsetService( 1245): New audio session: 160
I/HeadsetService( 1245): Selected configuration: bluetooth
V/qcbassboost( 306):	Effect_command: ctxt 0xb5e51470, cmd 5
V/qcbassboost( 306):	BassBoost_setParameter(): ctxt 0xb5e51470, param 1, value: 0
V/qcbassboost( 306):	BassBoost_setParameter() BASSBOOST_PARAM_STRENGTH value is 0
V/offload_effect_bundle( 306): effect_command: ctxt 0xb320aa80, cmd 5
V/offload_effect_bass_boost( 306): bassboost_set_parameter: ctxt 0xb320aa80, param 1
V/offload_effect_bass_boost( 306): bassboost_set_strength: ctxt 0xb320aa80, strength: 0
E/MediaPlayer( 9039): Should have subtitle controller already set
V/offload_effect_bundle( 306): effect_command: ctxt 0xb126f580, cmd 5
V/offload_effect_equalizer( 306): equalizer_set_parameter: ctxt 0xb126f580, param 2
V/offload_effect_equalizer( 306): equalizer_set_band_level: ctxt 0xb126f580, band: 0, level: 520
V/offload_effect_bundle( 306): effect_command: ctxt 0xb126f580, cmd 5
V/offload_effect_equalizer( 306): equalizer_set_parameter: ctxt 0xb126f580, param 2
V/offload_effect_equalizer( 306): equalizer_set_band_level: ctxt 0xb126f580, band: 1, level: 440
V/offload_effect_bundle( 306): effect_command: ctxt 0xb126f580, cmd 5
V/offload_effect_equalizer( 306): equalizer_set_parameter: ctxt 0xb126f580, param 2
V/offload_effect_equalizer( 306): equalizer_set_band_level: ctxt 0xb126f580, band: 2, level: 0
V/offload_effect_bundle( 306): effect_command: ctxt 0xb126f580, cmd 5
V/offload_effect_equalizer( 306): equalizer_set_parameter: ctxt 0xb126f580, param 2
V/offload_effect_equalizer( 306): equalizer_set_band_level: ctxt 0xb126f580, band: 3, level: 0
V/offload_effect_bundle( 306): effect_command: ctxt 0xb126f580, cmd 5
V/offload_effect_equalizer( 306): equalizer_set_parameter: ctxt 0xb126f580, param 2
V/offload_effect_equalizer( 306): equalizer_set_band_level: ctxt 0xb126f580, band: 4, level: 400
V/offload_effect_bundle( 306): effect_command: ctxt 0xb126f580, cmd 5
V/offload_effect_equalizer( 306): equalizer_set_parameter: ctxt 0xb126f580, param 2
E/HeadsetService( 1245): Error enabling equalizer!
E/HeadsetService( 1245): java.lang.IllegalArgumentException: AudioEffect: bad parameter value
E/HeadsetService( 1245):	at android.media.audiofx.AudioEffect.checkStatus(AudioEffect.java:1264)
E/HeadsetService( 1245):	at android.media.audiofx.Equalizer.setBandLevel(Equalizer.java:223)
E/HeadsetService( 1245):	at com.bel.android.dspmanager.service.HeadsetService.updateDsp(HeadsetService.java:306)
E/HeadsetService( 1245):	at com.bel.android.dspmanager.service.HeadsetService.updateDsp(HeadsetService.java:270)
E/HeadsetService( 1245):	at com.bel.android.dspmanager.service.HeadsetService$1.onReceive(HeadsetService.java:124)
E/HeadsetService( 1245):	at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:862)
E/HeadsetService( 1245):	at android.os.Handler.handleCallback(Handler.java:739)
E/HeadsetService( 1245):	at android.os.Handler.dispatchMessage(Handler.java:95)
E/HeadsetService( 1245):	at android.os.Looper.loop(Looper.java:135)
E/HeadsetService( 1245):	at android.app.ActivityThread.main(ActivityThread.java:5256)
E/HeadsetService( 1245):	at java.lang.reflect.Method.invoke(Native Method)
E/HeadsetService( 1245):	at java.lang.reflect.Method.invoke(Method.java:372)
E/HeadsetService( 1245):	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:898)
E/HeadsetService( 1245):	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)

I tried the stock music player a number of weeks back and got the same behaviour. My solution at the moment is to simply leave the equalizer disabled.