OpenSL ES decode 24bit FLAC

Question

I am trying to decode a FLAC file with 24bit sample format using OpenSL ES on Android. Originally, I had my SLDataFormat_PCM for the SLDataSink setup like this.

_pcm.formatType = SL_DATAFORMAT_PCM;
_pcm.numChannels = 2;
_pcm.samplesPerSec = SL_SAMPLINGRATE_44_1;
_pcm.bitsPerSample = SL_PCMSAMPLEFORMAT_FIXED_16;
_pcm.containerSize = SL_PCMSAMPLEFORMAT_FIXED_16;
_pcm.channelMask = SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT;
_pcm.endianness = SL_BYTEORDER_LITTLEENDIAN;

This is working well for basically any data format. Luckily the samplesPerSec is not respected (I don't want resampling).

Now I want to support the full bit-depth of a FLAC file with 24bit samples. When using this format, it apparently performs a bit-depth conversion, because once I load the file, and then check the ANDROID_KEY_PCMFORMAT_BITSPERSAMPLE info, it is 16.

When I put bitsPerSample = SL_PCMSAMPLEFORMAT_FIXED_24; or SL_PCMSAMPLEFORMAT_FIXED_32, then OpenSL ES rejects it

E/libOpenSLES(22706): pAudioSnk: bitsPerSample=32
W/libOpenSLES(22706): Leaving Engine::CreateAudioPlayer (SL_RESULT_CONTENT_UNSUPPORTED)

Any idea how this is meant to work? Is Android currently restricted to 16 bit int only? I would also accept 32bit float, but I don't suppose that will work either.

Answer 1

Currently it only supports 8 and 16 bits

Sources:

• Android source code (line 60)
• Article (PCM data format section)