OpenSL/ES : maximum volume of AudioPlayer

[mootoh]

From the document in r6 (docs/opensles/chart1.png), it looks we can get/set the volume of AudioPlayer object via VolumeItf.

The result is however, the return value of GetMaxVolumeLevel() is always 0, thus I canot set the volume anything but 0.

Am I missing something?

I tweaked the sample code (samples/native-audio) to get/set the volume like:

    const SLInterfaceID ids[2] = {SL_IID_SEEK, SL_IID_VOLUME};

    const SLboolean req[2] = {SL_BOOLEAN_TRUE, SL_BOOLEAN_TRUE};

    (*engineEngine)->CreateAudioPlayer(engineEngine, &fdPlayerObject, &audioSrc, &audioSnk, 2, ids, req);

    (*fdPlayerObject)->Realize(fdPlayerObject, SL_BOOLEAN_FALSE);

    SLVolumeItf volumeIf;

    (*fdPlayerObject)->GetInterface(fdPlayerObject, SL_IID_VOLUME, &volumeIf);

    SLmillibel maxVolume;

    (*volumeIf_)->GetMaxVolumeLevel(volumeIf, &maxVolume);

maxVolume => 0

I'm on NDK r6, Nexus S, OS 2.3.4.

Thanks in advance,

[mic _]

On Android the max level is 0 (unity gain). You can go below that (negative values), but you can't go above 0.

/Michael

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[mootoh]

Thanks mic, it works!

[Crazii]

I'm working on NDK now, and have this problem.
Here's my solution, Just in case anyone encounter this problem:

according to the doc, the volume ranges from [[SL_MILLIBEL_MIN, GetMaxVolumeLevel()].
so we can use a normalized scalar [0,1] to set the volume.

float nvolume = 0.5;

//get min & max
SLmillibel MinVolume = SL_MILLIBEL_MIN;
SLmillibel MaxVolume = SL_MILLIBEL_MIN;
(*SLES_Volume)->GetMaxVolumeLevel(SLES_Volume, &MaxVolume);

//calc SLES volume
SLmillibel Volume = MinVolume + (SLmillibel)( ((float)(MaxVolume - MinVolume))*nvolume ) );

//set
(*SLES_Volume)->SetVolumeLevel(SLES_Volume, Volume);

[Crazii]

It seems that the dB is not linear

"The definitions of the decibel and bel use base 10 logarithms."  (http://en.wikipedia.org/wiki/Decibel)

Now I use the formula: int dBVolume = 20* log2(x)/log2(10);

SLmillibel volume = dBVolume*100; //1dB = 100mB