Function DecodeAndConvertInt16

src/audio_resampler.cpp:120–182

* Utility function used to convert a buffer of a arbitrary AudioDecoder::Format to a int16 buffer * * @param[in] wrapped_decoder The decoder from which audio samples are read * @param[inout] buffer The buffer which will receive the converted samples, * has to be at least amount_of_samples_to_read*max(sizeof(int16_t),input_samplesize) bytes big. * @param[in] amount_of_samples_to_read The num

 *		If the returned value has a negative value an error occured.
 */
inline static int DecodeAndConvertInt16(AudioDecoderBase* wrapped_decoder,
										uint8_t * buffer,
										int amount_of_samples_to_read,
										const int input_samplesize,
										const AudioDecoder::Format input_format){
	int16_t* bufferAsInt16 = (int16_t*)buffer;

	//Workaround for decoders which don't detect their own end
	if (wrapped_decoder->IsFinished())
		return 0;

	int amount_of_samples_read = wrapped_decoder->Decode(buffer, amount_of_samples_to_read*input_samplesize);
	if (amount_of_samples_read <= 0) {
		return amount_of_samples_read; //error occured - or nothing read
	} else {
		//Convert the number of bytes to the number of samples
		amount_of_samples_read /= input_samplesize;
	}
	//Convert the read data (amount_of_data_read is at least one at this moment)
	switch (input_format) {
		case AudioDecoder::Format::S8:
			//Convert inplace (the last frames are unused if smaller)
			for (int i = amount_of_samples_read - 1; i >= 0; i--) {
				bufferAsInt16[i] = ((int8_t*)bufferAsInt16)[i] << 8;
			}
			break;
		case AudioDecoder::Format::U8:
			//Convert inplace (the last frames are unused if smaller)
			for (int i = amount_of_samples_read - 1; i >= 0; i--) {
				bufferAsInt16[i] = (((int16_t)(((uint8_t*)bufferAsInt16)[i])) - 128) << 8;
			}
			break;
		case AudioDecoder::Format::S16:
			//Nothing to convert
			break;
		case AudioDecoder::Format::U16:
			//Convert unsigned to signed
			for (int i = amount_of_samples_read - 1; i >= 0; i--) {
				bufferAsInt16[i] = (int16_t)(((int32_t)(((uint16_t*)bufferAsInt16)[i])) - 32768);
			}
			break;
		case AudioDecoder::Format::S32:
			//Convert inplace (from front to back to prevent overwriting the buffer)
			for (int i = 0; i < amount_of_samples_read; i++) {
				bufferAsInt16[i] = (int16_t)((((int32_t*)bufferAsInt16)[i]) >> 16);
			}
			break;
		case AudioDecoder::Format::U32:
			//Convert inplace (from front to back to prevent overwriting the buffer)
			for (int i = 0; i < amount_of_samples_read; i++) {
				bufferAsInt16[i] = (int16_t)(((int32_t)((((uint32_t*)bufferAsInt16)[i]) >> 16)) - 32768);
			}
			break;
		case AudioDecoder::Format::F32:
			//Convert inplace (from front to back to prevent overwriting the buffer)
			for (int i = 0; i < amount_of_samples_read; i++) {
				float number = ((((float*)bufferAsInt16)[i])*32768.0);
				bufferAsInt16[i] = (number <= 32767.0) ? ((number >= -32768.0) ? number : -32768) : 32767;