/**
* Creates an {@code AudioFrame} object based on the given header field. If the header field
* contains invalid values, result is <b>null</b>.
*
* @param bits the header bit field
* @return the {@code AudioFrame}
*/
private static AudioFrame createHeader(HeaderBitField bits) {
if (bits.get(21, 23) != 7) {
return null;
}
int mpegVer = bits.get(19, 20);
int layer = bits.get(17, 18);
int bitRateCode = bits.get(12, 15);
int sampleRateCode = bits.get(10, 11);
int padding = bits.get(9);
if (mpegVer == 1
|| layer == 0
|| bitRateCode == 0
|| bitRateCode == 15
|| sampleRateCode == 3) {
// invalid header values
return null;
}
int bitRate = calculateBitRate(mpegVer, layer, bitRateCode);
int sampleRate = calculateSampleRate(mpegVer, sampleRateCode);
int length = calculateFrameLength(layer, bitRate, sampleRate, padding);
float duration = calculateDuration(layer, sampleRate);
int channels = calculateChannels(bits.get(6, 7));
return new AudioFrame(mpegVer, layer, bitRate, sampleRate, channels, length, duration);
}
