/**
* Constructor, sets the input stream to read the Wav file from.
*
* @param stream The input stream.
* @throws Exception in case the input stream couldn't be read properly
*/
public WaveDecoder(InputStream stream) throws Exception {
if (stream == null) throw new IllegalArgumentException("Input stream must not be null");
in = new EndianDataInputStream(new BufferedInputStream(stream, 1024 * 1024));
if (!in.read4ByteString().equals("RIFF")) throw new IllegalArgumentException("not a wav");
in.readIntLittleEndian();
if (!in.read4ByteString().equals("WAVE"))
throw new IllegalArgumentException("expected WAVE tag");
if (!in.read4ByteString().equals("fmt "))
throw new IllegalArgumentException("expected fmt tag");
if (in.readIntLittleEndian() != 16)
throw new IllegalArgumentException("expected wave chunk size to be 16");
if (in.readShortLittleEndian() != 1)
throw new IllegalArgumentException("expected format to be 1");
channels = in.readShortLittleEndian();
sampleRate = in.readIntLittleEndian();
if (sampleRate != 44100) throw new IllegalArgumentException("Not 44100 sampling rate");
in.readIntLittleEndian();
in.readShortLittleEndian();
int fmt = in.readShortLittleEndian();
if (fmt != 16) throw new IllegalArgumentException("Only 16-bit signed format supported");
if (!in.read4ByteString().equals("data")) throw new RuntimeException("expected data tag");
in.readIntLittleEndian();
}
/**
* Tries to read in samples.length samples, merging stereo to a mono channel by averaging and
* converting non float formats to float 32-bit. Returns the number of samples actually read.
* Guarantees that samples.length samples are read in if there was enough data in the stream.
*
* @param samples The samples array to write the samples to
* @return The number of samples actually read.
*/
public int readSamples(float[] samples) {
int readSamples = 0;
for (int i = 0; i < samples.length; i++) {
float sample = 0;
try {
for (int j = 0; j < channels; j++) {
int shortValue = in.readShortLittleEndian();
sample += (shortValue * MAX_VALUE);
}
sample /= channels;
samples[i] = sample;
readSamples++;
} catch (Exception ex) {
break;
}
}
return readSamples;
}
