Android flac to wav

╰半夏微凉° 2024-03-26 14:55 21阅读 0赞

## Android flac to wav ##

flac格式的音频属于“无损压缩”，对于我们最常说的“无损音频”来说，一般都是指传统CD格式中的16bit/44.1kHz采样率的文件格式，而知所以称为无损压缩，也是因为其包含了20Hz-22.05kHz这个完全覆盖人耳可闻范围的频响频率而得名。

##### **简介** #####

FLAC即是FreeLossless Audio Codec的缩写，全称应该叫OGGFLAC，中文可解为无损音频压缩编码。它是OGG计划的一部分，当然也就是开源、免费的了，这也难怪它这么快就得到了多家MP3厂商的支持。

FLAC是一套著名的自由音频压缩编码，其特点是无损压缩。FLAC压缩比可以达到2：1，对于无损压缩来说，这已经是相当高的比例了；而且它解码速度快，只需进行整数运算即可完成整个解码过程，对CPU的运算能力要求很低，所以普通的随身听，都可以轻松实现实时解码。

不同于其他有损压缩编码如MP3 及AAC，它不会破坏任何原有的音频资讯，所以可以还原音乐光盘音质。现在它已被很多软件及硬件音频产品所支持。简而言之，FLAC与MP3相仿，但是是无损压缩的，也就是说音频以FLAC方式压缩不会丢失任何信息。这种压缩与Zip的方式类似，但是FLAC将给你更大的压缩比率，因为

FLAC是专门针对音频的特点设计的压缩方式，并且你可以使用播放器播放FLAC压缩的文件，就象通常播放你的MP3文件一样。

**补充：为无损格式，较ape而言，他体积大点，但是兼容性好，编码速度快，播放器支持更广**

##### **flac与mp3的区别** #####

音质不同：flac不会破坏任何原有的音频信息，可以还原音乐光盘音质。mp3旨在大大减少音频数据量，利用mpeg音频第三层技术，将音乐压缩成1：10甚至1：12的小文件。压缩比不同：flac是一种专为pcm音频特性而设计的压缩模式，可以使用播放器直接播放FLAC压缩的文件。mp3其优点是压缩后占用空间小，适用于移动设备的存储和使用。

1、音质不同：flac不会破坏任何原有的音频信息，可以还原音乐光盘音质。mp3旨在大大减少音频数据量，利用mpeg音频第三层技术，将音乐压缩成1：10甚至1：12的小文件。

2、音频不同：flac音频以FLAC编码压缩后不会丢失任何信息，将FLAC文件还原为WAV文件后，与压缩前的WAV文件内容相同。mp3利用人耳对高频声音信号不敏感的特性，将时域波形信号转换成频域信号，并划分成多个频段，对不同的频段使用不同的压缩率，对高频加大压缩比对低频信号使用小压缩比，保证信号不失真。

3、压缩比不同：flac是一种专为pcm音频特性而设计的压缩模式，可以使用播放器直接播放FLAC压缩的文件。mp3其优点是压缩后占用空间小，适用于移动设备的存储和使用。

##### 使用[FLAC-library-Java][]库来实现 flac与wav互转。 #####

###### 1.flac to wav ######

import java.io.*;
    import java.nio.charset.StandardCharsets;
    import java.util.Arrays;
    import java.util.zip.DataFormatException;
    
    
    public final class SimpleDecodeFlacToWav {
    	
    	public static void main(String[] args) throws IOException, DataFormatException {
    		if (args.length != 2) {
    			System.err.println("Usage: java SimpleDecodeFlacToWav InFile.flac OutFile.wav");
    			System.exit(1);
    			return;
    		}
    		try (BitInputStream in = new BitInputStream(new BufferedInputStream(new FileInputStream(args[0])));
    				OutputStream out = new BufferedOutputStream(new FileOutputStream(args[1]))) {
    			decodeFile(in, out);
    		}
    	}
    	
    	
    	public static void decodeFile(BitInputStream in, OutputStream out) throws IOException, DataFormatException {
    		// Handle FLAC header and metadata blocks
    		if (in.readUint(32) != 0x664C6143)
    			throw new DataFormatException("Invalid magic string");
    		int sampleRate = -1;
    		int numChannels = -1;
    		int sampleDepth = -1;
    		long numSamples = -1;
    		for (boolean last = false; !last; ) {
    			last = in.readUint(1) != 0;
    			int type = in.readUint(7);
    			int length = in.readUint(24);
    			if (type == 0) {  // Stream info block
    				in.readUint(16);
    				in.readUint(16);
    				in.readUint(24);
    				in.readUint(24);
    				sampleRate = in.readUint(20);
    				numChannels = in.readUint(3) + 1;
    				sampleDepth = in.readUint(5) + 1;
    				numSamples = (long)in.readUint(18) << 18 | in.readUint(18);
    				for (int i = 0; i < 16; i++)
    					in.readUint(8);
    			} else {
    				for (int i = 0; i < length; i++)
    					in.readUint(8);
    			}
    		}
    		if (sampleRate == -1)
    			throw new DataFormatException("Stream info metadata block absent");
    		if (sampleDepth % 8 != 0)
    			throw new RuntimeException("Sample depth not supported");
    		
    		// Start writing WAV file headers
    		long sampleDataLen = numSamples * numChannels * (sampleDepth / 8);
    		writeString("RIFF", out);
    		writeLittleInt(4, (int)sampleDataLen + 36, out);
    		writeString("WAVE", out);
    		writeString("fmt ", out);
    		writeLittleInt(4, 16, out);
    		writeLittleInt(2, 0x0001, out);
    		writeLittleInt(2, numChannels, out);
    		writeLittleInt(4, sampleRate, out);
    		writeLittleInt(4, sampleRate * numChannels * (sampleDepth / 8), out);
    		writeLittleInt(2, numChannels * (sampleDepth / 8), out);
    		writeLittleInt(2, sampleDepth, out);
    		writeString("data", out);
    		writeLittleInt(4, (int)sampleDataLen, out);
    		
    		// Decode FLAC audio frames and write raw samples
    		while (decodeFrame(in, numChannels, sampleDepth, out));
    	}
    	
    	
    	private static void writeLittleInt(int numBytes, int val, OutputStream out) throws IOException {
    		for (int i = 0; i < numBytes; i++)
    			out.write(val >>> (i * 8));
    	}
    	
    	private static void writeString(String s, OutputStream out) throws IOException {
    		out.write(s.getBytes(StandardCharsets.UTF_8));
    	}
    	
    	
    	private static boolean decodeFrame(BitInputStream in, int numChannels, int sampleDepth, OutputStream out)
    			throws IOException, DataFormatException {
    		// Read a ton of header fields, and ignore most of them
    		int temp = in.readByte();
    		if (temp == -1)
    			return false;
    		int sync = temp << 6 | in.readUint(6);
    		if (sync != 0x3FFE)
    			throw new DataFormatException("Sync code expected");
    		
    		in.readUint(1);
    		in.readUint(1);
    		int blockSizeCode = in.readUint(4);
    		int sampleRateCode = in.readUint(4);
    		int chanAsgn = in.readUint(4);
    		in.readUint(3);
    		in.readUint(1);
    		
    		temp = Integer.numberOfLeadingZeros(~(in.readUint(8) << 24)) - 1;
    		for (int i = 0; i < temp; i++)
    			in.readUint(8);
    		
    		int blockSize;
    		if (blockSizeCode == 1)
    			blockSize = 192;
    		else if (2 <= blockSizeCode && blockSizeCode <= 5)
    			blockSize = 576 << (blockSizeCode - 2);
    		else if (blockSizeCode == 6)
    			blockSize = in.readUint(8) + 1;
    		else if (blockSizeCode == 7)
    			blockSize = in.readUint(16) + 1;
    		else if (8 <= blockSizeCode && blockSizeCode <= 15)
    			blockSize = 256 << (blockSizeCode - 8);
    		else
    			throw new DataFormatException("Reserved block size");
    		
    		if (sampleRateCode == 12)
    			in.readUint(8);
    		else if (sampleRateCode == 13 || sampleRateCode == 14)
    			in.readUint(16);
    		
    		in.readUint(8);
    		
    		// Decode each channel's subframe, then skip footer
    		int[][] samples = new int[numChannels][blockSize];
    		decodeSubframes(in, sampleDepth, chanAsgn, samples);
    		in.alignToByte();
    		in.readUint(16);
    		
    		// Write the decoded samples
    		for (int i = 0; i < blockSize; i++) {
    			for (int j = 0; j < numChannels; j++) {
    				int val = samples[j][i];
    				if (sampleDepth == 8)
    					val += 128;
    				writeLittleInt(sampleDepth / 8, val, out);
    			}
    		}
    		return true;
    	}
    	
    	
    	private static void decodeSubframes(BitInputStream in, int sampleDepth, int chanAsgn, int[][] result)
    			throws IOException, DataFormatException {
    		int blockSize = result[0].length;
    		long[][] subframes = new long[result.length][blockSize];
    		if (0 <= chanAsgn && chanAsgn <= 7) {
    			for (int ch = 0; ch < result.length; ch++)
    				decodeSubframe(in, sampleDepth, subframes[ch]);
    		} else if (8 <= chanAsgn && chanAsgn <= 10) {
    			decodeSubframe(in, sampleDepth + (chanAsgn == 9 ? 1 : 0), subframes[0]);
    			decodeSubframe(in, sampleDepth + (chanAsgn == 9 ? 0 : 1), subframes[1]);
    			if (chanAsgn == 8) {
    				for (int i = 0; i < blockSize; i++)
    					subframes[1][i] = subframes[0][i] - subframes[1][i];
    			} else if (chanAsgn == 9) {
    				for (int i = 0; i < blockSize; i++)
    					subframes[0][i] += subframes[1][i];
    			} else if (chanAsgn == 10) {
    				for (int i = 0; i < blockSize; i++) {
    					long side = subframes[1][i];
    					long right = subframes[0][i] - (side >> 1);
    					subframes[1][i] = right;
    					subframes[0][i] = right + side;
    				}
    			}
    		} else
    			throw new DataFormatException("Reserved channel assignment");
    		for (int ch = 0; ch < result.length; ch++) {
    			for (int i = 0; i < blockSize; i++)
    				result[ch][i] = (int)subframes[ch][i];
    		}
    	}
    	
    	
    	private static void decodeSubframe(BitInputStream in, int sampleDepth, long[] result)
    			throws IOException, DataFormatException {
    		in.readUint(1);
    		int type = in.readUint(6);
    		int shift = in.readUint(1);
    		if (shift == 1) {
    			while (in.readUint(1) == 0)
    				shift++;
    		}
    		sampleDepth -= shift;
    		
    		if (type == 0)  // Constant coding
    			Arrays.fill(result, 0, result.length, in.readSignedInt(sampleDepth));
    		else if (type == 1) {  // Verbatim coding
    			for (int i = 0; i < result.length; i++)
    				result[i] = in.readSignedInt(sampleDepth);
    		} else if (8 <= type && type <= 12)
    			decodeFixedPredictionSubframe(in, type - 8, sampleDepth, result);
    		else if (32 <= type && type <= 63)
    			decodeLinearPredictiveCodingSubframe(in, type - 31, sampleDepth, result);
    		else
    			throw new DataFormatException("Reserved subframe type");
    		
    		for (int i = 0; i < result.length; i++)
    			result[i] <<= shift;
    	}
    	
    	
    	private static void decodeFixedPredictionSubframe(BitInputStream in, int predOrder, int sampleDepth, long[] result)
    			throws IOException, DataFormatException {
    		for (int i = 0; i < predOrder; i++)
    			result[i] = in.readSignedInt(sampleDepth);
    		decodeResiduals(in, predOrder, result);
    		restoreLinearPrediction(result, FIXED_PREDICTION_COEFFICIENTS[predOrder], 0);
    	}
    	
    	private static final int[][] FIXED_PREDICTION_COEFFICIENTS = {
    		{},
    		{1},
    		{2, -1},
    		{3, -3, 1},
    		{4, -6, 4, -1},
    	};
    	
    	
    	private static void decodeLinearPredictiveCodingSubframe(BitInputStream in, int lpcOrder, int sampleDepth, long[] result)
    			throws IOException, DataFormatException {
    		for (int i = 0; i < lpcOrder; i++)
    			result[i] = in.readSignedInt(sampleDepth);
    		int precision = in.readUint(4) + 1;
    		int shift = in.readSignedInt(5);
    		int[] coefs = new int[lpcOrder];
    		for (int i = 0; i < coefs.length; i++)
    			coefs[i] = in.readSignedInt(precision);
    		decodeResiduals(in, lpcOrder, result);
    		restoreLinearPrediction(result, coefs, shift);
    	}
    	
    	
    	private static void decodeResiduals(BitInputStream in, int warmup, long[] result) throws IOException, DataFormatException {
    		int method = in.readUint(2);
    		if (method >= 2)
    			throw new DataFormatException("Reserved residual coding method");
    		int paramBits = method == 0 ? 4 : 5;
    		int escapeParam = method == 0 ? 0xF : 0x1F;
    		
    		int partitionOrder = in.readUint(4);
    		int numPartitions = 1 << partitionOrder;
    		if (result.length % numPartitions != 0)
    			throw new DataFormatException("Block size not divisible by number of Rice partitions");
    		int partitionSize = result.length / numPartitions;
    		
    		for (int i = 0; i < numPartitions; i++) {
    			int start = i * partitionSize + (i == 0 ? warmup : 0);
    			int end = (i + 1) * partitionSize;
    			
    			int param = in.readUint(paramBits);
    			if (param < escapeParam) {
    				for (int j = start; j < end; j++)
    					result[j] = in.readRiceSignedInt(param);
    			} else {
    				int numBits = in.readUint(5);
    				for (int j = start; j < end; j++)
    					result[j] = in.readSignedInt(numBits);
    			}
    		}
    	}
    	
    	
    	private static void restoreLinearPrediction(long[] result, int[] coefs, int shift) {
    		for (int i = coefs.length; i < result.length; i++) {
    			long sum = 0;
    			for (int j = 0; j < coefs.length; j++)
    				sum += result[i - 1 - j] * coefs[j];
    			result[i] += sum >> shift;
    		}
    	}
    	
    }
    
    
    
    final class BitInputStream implements AutoCloseable {
    	
    	private InputStream in;
    	private long bitBuffer;
    	private int bitBufferLen;
    	
    	
    	public BitInputStream(InputStream in) {
    		this.in = in;
    	}
    	
    	
    	public void alignToByte() {
    		bitBufferLen -= bitBufferLen % 8;
    	}
    	
    	
    	public int readByte() throws IOException {
    		if (bitBufferLen >= 8)
    			return readUint(8);
    		else
    			return in.read();
    	}
    	
    	
    	public int readUint(int n) throws IOException {
    		while (bitBufferLen < n) {
    			int temp = in.read();
    			if (temp == -1)
    				throw new EOFException();
    			bitBuffer = (bitBuffer << 8) | temp;
    			bitBufferLen += 8;
    		}
    		bitBufferLen -= n;
    		int result = (int)(bitBuffer >>> bitBufferLen);
    		if (n < 32)
    			result &= (1 << n) - 1;
    		return result;
    	}
    	
    	
    	public int readSignedInt(int n) throws IOException {
    		return (readUint(n) << (32 - n)) >> (32 - n);
    	}
    	
    	
    	public long readRiceSignedInt(int param) throws IOException {
    		long val = 0;
    		while (readUint(1) == 0)
    			val++;
    		val = (val << param) | readUint(param);
    		return (val >>> 1) ^ -(val & 1);
    	}
    	
    	
    	public void close() throws IOException {
    		in.close();
    	}
    	
    }

###### 2. wav to flac ######

import java.io.*;
    import java.nio.charset.StandardCharsets;
    import java.util.zip.DataFormatException;
    
    
    public final class SimpleEncodeWavToFlac {
    	
    	public static void main(String[] args) throws IOException, DataFormatException {
    		if (args.length != 2) {
    			System.err.println("Usage: java SimpleEncodeWavToFlac InFile.wav OutFile.flac");
    			System.exit(1);
    			return;
    		}
    		try (InputStream in = new BufferedInputStream(new FileInputStream(args[0]));
    				BitOutputStream out = new BitOutputStream(new BufferedOutputStream(new FileOutputStream(args[1])))) {
    			encodeFile(in, out);
    		}
    	}
    	
    	
    	public static void encodeFile(InputStream in, BitOutputStream out) throws IOException, DataFormatException {
    		// Read and parse WAV file headers
    		if (!readString(in, 4).equals("RIFF"))
    			throw new DataFormatException("Invalid RIFF file header");
    		readLittleInt(in, 4);
    		if (!readString(in, 4).equals("WAVE"))
    			throw new DataFormatException("Invalid WAV file header");
    		
    		if (!readString(in, 4).equals("fmt "))
    			throw new DataFormatException("Unrecognized WAV file chunk");
    		if (readLittleInt(in, 4) != 16)
    			throw new DataFormatException("Unsupported WAV file type");
    		if (readLittleInt(in, 2) != 0x0001)
    			throw new DataFormatException("Unsupported WAV file codec");
    		int numChannels = readLittleInt(in, 2);
    		if (numChannels < 0 || numChannels > 8)
    			throw new RuntimeException("Too many (or few) audio channels");
    		int sampleRate = readLittleInt(in, 4);
    		if (sampleRate <= 0 || sampleRate >= (1 << 20))
    			throw new RuntimeException("Sample rate too large or invalid");
    		readLittleInt(in, 4);
    		readLittleInt(in, 2);
    		int sampleDepth = readLittleInt(in, 2);
    		if (sampleDepth == 0 || sampleDepth > 32 || sampleDepth % 8 != 0)
    			throw new RuntimeException("Unsupported sample depth");
    		
    		if (!readString(in, 4).equals("data"))
    			throw new DataFormatException("Unrecognized WAV file chunk");
    		int sampleDataLen = readLittleInt(in, 4);
    		if (sampleDataLen <= 0 || sampleDataLen % (numChannels * (sampleDepth / 8)) != 0)
    			throw new DataFormatException("Invalid length of audio sample data");
    		
    		// Start writing FLAC file header and stream info metadata block
    		out.writeInt(32, 0x664C6143);
    		out.writeInt(1, 1);
    		out.writeInt(7, 0);
    		out.writeInt(24, 34);
    		out.writeInt(16, BLOCK_SIZE);
    		out.writeInt(16, BLOCK_SIZE);
    		out.writeInt(24, 0);
    		out.writeInt(24, 0);
    		out.writeInt(20, sampleRate);
    		out.writeInt(3, numChannels - 1);
    		out.writeInt(5, sampleDepth - 1);
    		int numSamples = sampleDataLen / (numChannels * (sampleDepth / 8));
    		out.writeInt(18, numSamples >>> 18);
    		out.writeInt(18, numSamples >>>  0);
    		for (int i = 0; i < 16; i++)
    			out.writeInt(8, 0);
    		
    		// Read raw samples and encode FLAC audio frames
    		for (int i = 0; numSamples > 0; i++) {
    			int blockSize = Math.min(numSamples, BLOCK_SIZE);
    			encodeFrame(in, i, numChannels, sampleDepth, sampleRate, blockSize, out);
    			numSamples -= blockSize;
    		}
    	}
    	
    	
    	private static final int BLOCK_SIZE = 4096;
    	
    	
    	private static String readString(InputStream in, int len) throws IOException {
    		byte[] temp = new byte[len];
    		for (int i = 0; i < temp.length; i++) {
    			int b = in.read();
    			if (b == -1)
    				throw new EOFException();
    			temp[i] = (byte)b;
    		}
    		return new String(temp, StandardCharsets.UTF_8);
    	}
    	
    	
    	private static int readLittleInt(InputStream in, int n) throws IOException {
    		int result = 0;
    		for (int i = 0; i < n; i++) {
    			int b = in.read();
    			if (b == -1)
    				throw new EOFException();
    			result |= b << (i * 8);
    		}
    		return result;
    	}
    	
    	
    	private static void encodeFrame(InputStream in, int frameIndex, int numChannels, int sampleDepth, int sampleRate, int blockSize, BitOutputStream out) throws IOException {
    		int[][] samples = new int[numChannels][blockSize];
    		int bytesPerSample = sampleDepth / 8;
    		for (int i = 0; i < blockSize; i++) {
    			for (int ch = 0; ch < numChannels; ch++) {
    				int val = 0;
    				for (int j = 0; j < bytesPerSample; j++) {
    					int b = in.read();
    					if (b == -1)
    						throw new EOFException();
    					val |= b << (j * 8);
    				}
    				if (sampleDepth == 8)
    					samples[ch][i] = val - 128;
    				else
    					samples[ch][i] = (val << (32 - sampleDepth)) >> (32 - sampleDepth);
    			}
    		}
    		
    		out.resetCrcs();
    		out.writeInt(14, 0x3FFE);
    		out.writeInt(1, 0);
    		out.writeInt(1, 0);
    		out.writeInt(4, 7);
    		out.writeInt(4, sampleRate % 10 == 0 ? 14 : 13);
    		out.writeInt(4, numChannels - 1);
    		switch (sampleDepth) {
    			case  8:  out.writeInt(3, 1);  break;
    			case 16:  out.writeInt(3, 4);  break;
    			case 24:  out.writeInt(3, 6);  break;
    			case 32:  out.writeInt(3, 0);  break;
    			default:  throw new IllegalArgumentException();
    		}
    		out.writeInt(1, 0);
    		out.writeInt(8, 0xFC | (frameIndex >>> 30));
    		for (int i = 24; i >= 0; i -= 6)
    			out.writeInt(8, 0x80 | ((frameIndex >>> i) & 0x3F));
    		out.writeInt(16, blockSize - 1);
    		out.writeInt(16, sampleRate / (sampleRate % 10 == 0 ? 10 : 1));
    		out.writeInt(8, out.crc8);
    		
    		for (int[] chanSamples : samples)
    			encodeSubframe(chanSamples, sampleDepth, out);
    		out.alignToByte();
    		out.writeInt(16, out.crc16);
    	}
    	
    	
    	private static void encodeSubframe(int[] samples, int sampleDepth, BitOutputStream out) throws IOException {
    		out.writeInt(1, 0);
    		out.writeInt(6, 1);  // Verbatim coding
    		out.writeInt(1, 0);
    		for (int x : samples)
    			out.writeInt(sampleDepth, x);
    	}
    	
    }
    
    
    
    final class BitOutputStream implements AutoCloseable {
    	
    	private OutputStream out;
    	private long bitBuffer;
    	private int bitBufferLen;
    	public int crc8;
    	public int crc16;
    	
    	
    	public BitOutputStream(OutputStream out) {
    		this.out = out;
    		bitBuffer = 0;
    		bitBufferLen = 0;
    		resetCrcs();
    	}
    	
    	
    	public void resetCrcs() {
    		crc8 = 0;
    		crc16 = 0;
    	}
    	
    	
    	public void alignToByte() throws IOException {
    		writeInt((64 - bitBufferLen) % 8, 0);
    	}
    	
    	
    	public void writeInt(int n, int val) throws IOException {
    		bitBuffer = (bitBuffer << n) | (val & ((1L << n) - 1));
    		bitBufferLen += n;
    		while (bitBufferLen >= 8) {
    			bitBufferLen -= 8;
    			int b = (int)(bitBuffer >>> bitBufferLen) & 0xFF;
    			out.write(b);
    			crc8 ^= b;
    			crc16 ^= b << 8;
    			for (int i = 0; i < 8; i++) {
    				crc8 = (crc8 << 1) ^ ((crc8 >>> 7) * 0x107);
    				crc16 = (crc16 << 1) ^ ((crc16 >>> 15) * 0x18005);
    			}
    		}
    	}
    	
    	
    	public void close() throws IOException {
    		out.close();
    	}
    	
    }

###### 3.wav 2 flac ######

import java.io.*;
    import java.nio.charset.StandardCharsets;
    import java.util.zip.DataFormatException;
    
    
    public final class DecodeFlacResidueToWav {
    	
    	public static void main(String[] args) throws IOException, DataFormatException {
    		if (args.length != 2) {
    			System.err.println("Usage: java DecodeFlacResidueToWav InFile.flac OutFile.wav");
    			System.exit(1);
    			return;
    		}
    		try (BitInputStream in = new BitInputStream(new BufferedInputStream(new FileInputStream(args[0])));
    				OutputStream out = new BufferedOutputStream(new FileOutputStream(args[1]))) {
    			decodeFile(in, out);
    		}
    	}
    	
    	
    	public static void decodeFile(BitInputStream in, OutputStream out) throws IOException, DataFormatException {
    		// Handle FLAC header and metadata blocks
    		if (in.readUint(32) != 0x664C6143)
    			throw new DataFormatException("Invalid magic string");
    		int sampleRate = -1;
    		int numChannels = -1;
    		int sampleDepth = -1;
    		long numSamples = -1;
    		for (boolean last = false; !last; ) {
    			last = in.readUint(1) != 0;
    			int type = in.readUint(7);
    			int length = in.readUint(24);
    			if (type == 0) {  // Stream info block
    				in.readUint(16);
    				in.readUint(16);
    				in.readUint(24);
    				in.readUint(24);
    				sampleRate = in.readUint(20);
    				numChannels = in.readUint(3) + 1;
    				sampleDepth = in.readUint(5) + 1;
    				numSamples = (long)in.readUint(18) << 18 | in.readUint(18);
    				for (int i = 0; i < 16; i++)
    					in.readUint(8);
    			} else {
    				for (int i = 0; i < length; i++)
    					in.readUint(8);
    			}
    		}
    		if (sampleRate == -1)
    			throw new DataFormatException("Stream info metadata block absent");
    		if (sampleDepth % 8 != 0)
    			throw new RuntimeException("Sample depth not supported");
    		
    		// Start writing WAV file headers
    		long sampleDataLen = numSamples * numChannels * (sampleDepth / 8);
    		writeString("RIFF", out);
    		writeLittleInt(4, (int)sampleDataLen + 36, out);
    		writeString("WAVE", out);
    		writeString("fmt ", out);
    		writeLittleInt(4, 16, out);
    		writeLittleInt(2, 0x0001, out);
    		writeLittleInt(2, numChannels, out);
    		writeLittleInt(4, sampleRate, out);
    		writeLittleInt(4, sampleRate * numChannels * (sampleDepth / 8), out);
    		writeLittleInt(2, numChannels * (sampleDepth / 8), out);
    		writeLittleInt(2, sampleDepth, out);
    		writeString("data", out);
    		writeLittleInt(4, (int)sampleDataLen, out);
    		
    		// Decode FLAC audio frames and write raw samples
    		while (decodeFrame(in, numChannels, sampleDepth, out));
    	}
    	
    	
    	private static void writeLittleInt(int numBytes, int val, OutputStream out) throws IOException {
    		for (int i = 0; i < numBytes; i++)
    			out.write(val >>> (i * 8));
    	}
    	
    	private static void writeString(String s, OutputStream out) throws IOException {
    		out.write(s.getBytes(StandardCharsets.UTF_8));
    	}
    	
    	
    	private static boolean decodeFrame(BitInputStream in, int numChannels, int sampleDepth, OutputStream out) throws IOException, DataFormatException {
    		// Read a ton of header fields, and ignore most of them
    		int temp = in.readByte();
    		if (temp == -1)
    			return false;
    		int sync = temp << 6 | in.readUint(6);
    		if (sync != 0x3FFE)
    			throw new DataFormatException("Sync code expected");
    		
    		in.readUint(1);
    		in.readUint(1);
    		int blockSizeCode = in.readUint(4);
    		int sampleRateCode = in.readUint(4);
    		int chanAsgn = in.readUint(4);
    		in.readUint(3);
    		in.readUint(1);
    		
    		temp = Integer.numberOfLeadingZeros(~(in.readUint(8) << 24)) - 1;
    		for (int i = 0; i < temp; i++)
    			in.readUint(8);
    		
    		int blockSize;
    		if (blockSizeCode == 1)
    			blockSize = 192;
    		else if (2 <= blockSizeCode && blockSizeCode <= 5)
    			blockSize = 576 << (blockSizeCode - 2);
    		else if (blockSizeCode == 6)
    			blockSize = in.readUint(8) + 1;
    		else if (blockSizeCode == 7)
    			blockSize = in.readUint(16) + 1;
    		else if (8 <= blockSizeCode && blockSizeCode <= 15)
    			blockSize = 256 << (blockSizeCode - 8);
    		else
    			throw new DataFormatException("Reserved block size");
    		
    		if (sampleRateCode == 12)
    			in.readUint(8);
    		else if (sampleRateCode == 13 || sampleRateCode == 14)
    			in.readUint(16);
    		
    		in.readUint(8);
    		
    		// Decode each channel's subframe, then skip footer
    		int[][] samples = new int[numChannels][blockSize];
    		decodeSubframes(in, sampleDepth, chanAsgn, samples);
    		in.alignToByte();
    		in.readUint(16);
    		
    		// Write the decoded samples
    		for (int i = 0; i < blockSize; i++) {
    			for (int j = 0; j < numChannels; j++) {
    				int val = samples[j][i];
    				if (sampleDepth == 8)
    					val += 128;
    				writeLittleInt(sampleDepth / 8, val, out);
    			}
    		}
    		return true;
    	}
    	
    	
    	private static void decodeSubframes(BitInputStream in, int sampleDepth, int chanAsgn, int[][] result) throws IOException, DataFormatException {
    		int blockSize = result[0].length;
    		long[][] subframes = new long[result.length][blockSize];
    		if (0 <= chanAsgn && chanAsgn <= 7) {
    			for (int ch = 0; ch < result.length; ch++)
    				decodeSubframe(in, sampleDepth, subframes[ch]);
    		} else if (8 <= chanAsgn && chanAsgn <= 10) {
    			decodeSubframe(in, sampleDepth + (chanAsgn == 9 ? 1 : 0), subframes[0]);
    			decodeSubframe(in, sampleDepth + (chanAsgn == 9 ? 0 : 1), subframes[1]);
    		} else
    			throw new DataFormatException("Reserved channel assignment");
    		for (int ch = 0; ch < result.length; ch++) {
    			for (int i = 0; i < blockSize; i++)
    				result[ch][i] = (int)subframes[ch][i];
    		}
    	}
    	
    	
    	private static void decodeSubframe(BitInputStream in, int sampleDepth, long[] result) throws IOException, DataFormatException {
    		in.readUint(1);
    		int type = in.readUint(6);
    		int shift = in.readUint(1);
    		if (shift == 1) {
    			while (in.readUint(1) == 0)
    				shift++;
    		}
    		sampleDepth -= shift;
    		
    		if (type == 0)  // Constant coding
    			in.readSignedInt(sampleDepth);
    		else if (type == 1) {  // Verbatim coding
    			for (int i = 0; i < result.length; i++)
    				in.readSignedInt(sampleDepth);
    		} else if (8 <= type && type <= 12)
    			decodeFixedPredictionSubframe(in, type - 8, sampleDepth, result);
    		else if (32 <= type && type <= 63)
    			decodeLinearPredictiveCodingSubframe(in, type - 31, sampleDepth, result);
    		else
    			throw new DataFormatException("Reserved subframe type");
    		
    		for (int i = 0; i < result.length; i++)
    			result[i] <<= shift;
    	}
    	
    	
    	private static void decodeFixedPredictionSubframe(BitInputStream in, int predOrder, int sampleDepth, long[] result) throws IOException, DataFormatException {
    		for (int i = 0; i < predOrder; i++)
    			in.readSignedInt(sampleDepth);
    		decodeResiduals(in, predOrder, result);
    	}
    	
    	
    	private static void decodeLinearPredictiveCodingSubframe(BitInputStream in, int lpcOrder, int sampleDepth, long[] result) throws IOException, DataFormatException {
    		for (int i = 0; i < lpcOrder; i++)
    			in.readSignedInt(sampleDepth);
    		int precision = in.readUint(4) + 1;
    		in.readSignedInt(5);
    		for (int i = 0; i < lpcOrder; i++)
    			in.readSignedInt(precision);
    		decodeResiduals(in, lpcOrder, result);
    	}
    	
    	
    	private static void decodeResiduals(BitInputStream in, int warmup, long[] result) throws IOException, DataFormatException {
    		int method = in.readUint(2);
    		if (method >= 2)
    			throw new DataFormatException("Reserved residual coding method");
    		int paramBits = method == 0 ? 4 : 5;
    		int escapeParam = method == 0 ? 0xF : 0x1F;
    		
    		int partitionOrder = in.readUint(4);
    		int numPartitions = 1 << partitionOrder;
    		if (result.length % numPartitions != 0)
    			throw new DataFormatException("Block size not divisible by number of Rice partitions");
    		int partitionSize = result.length / numPartitions;
    		
    		for (int i = 0; i < numPartitions; i++) {
    			int start = i * partitionSize + (i == 0 ? warmup : 0);
    			int end = (i + 1) * partitionSize;
    			
    			int param = in.readUint(paramBits);
    			if (param < escapeParam) {
    				for (int j = start; j < end; j++)
    					result[j] = in.readRiceSignedInt(param);
    			} else {
    				int numBits = in.readUint(5);
    				for (int j = start; j < end; j++)
    					result[j] = in.readSignedInt(numBits);
    			}
    		}
    	}
    	
    }
    
    
    
    final class BitInputStream implements AutoCloseable {
    	
    	private InputStream in;
    	private long bitBuffer;
    	private int bitBufferLen;
    	
    	
    	public BitInputStream(InputStream in) {
    		this.in = in;
    	}
    	
    	
    	public void alignToByte() {
    		bitBufferLen -= bitBufferLen % 8;
    	}
    	
    	
    	public int readByte() throws IOException {
    		if (bitBufferLen >= 8)
    			return readUint(8);
    		else
    			return in.read();
    	}
    	
    	
    	public int readUint(int n) throws IOException {
    		while (bitBufferLen < n) {
    			int temp = in.read();
    			if (temp == -1)
    				throw new EOFException();
    			bitBuffer = (bitBuffer << 8) | temp;
    			bitBufferLen += 8;
    		}
    		bitBufferLen -= n;
    		int result = (int)(bitBuffer >>> bitBufferLen);
    		if (n < 32)
    			result &= (1 << n) - 1;
    		return result;
    	}
    	
    	
    	public int readSignedInt(int n) throws IOException {
    		return (readUint(n) << (32 - n)) >> (32 - n);
    	}
    	
    	
    	public long readRiceSignedInt(int param) throws IOException {
    		long val = 0;
    		while (readUint(1) == 0)
    			val++;
    		val = (val << param) | readUint(param);
    		return (val >>> 1) ^ -(val & 1);
    	}
    	
    	
    	public void close() throws IOException {
    		in.close();
    	}
    	
    }

###### 4.小结 ######

wav2flac的过程结束后，flac文件的体积没啥变化，没有压缩。可以播放。

###### 5.使用完整的jar包 ######

wav2flac的过程结束后，flac文件的体积会变小。可以播放。详情参考githup库

###### 6.资料 ######

[flac][]

[flac convert][]

[githup][FLAC-library-Java]

[FLAC-library-Java]: https://github.com/nayuki/FLAC-library-Java
[flac]: https://xiph.org/flac/format.html
[flac convert]: https://www.nayuki.io/page/flac-library-java