Additional metadata keys to be used in SLMetadataExtractionItf: the ANDROID_KEY_PCMFORMAT_* keys follow the fields of the SLDataFormat_PCM struct, and as such all values corresponding to these keys are of SLuint32 type, and are defined as the fields of the same name in SLDataFormat_PCM. The exception is that sample rate is expressed here in Hz units, rather than in milliHz units.