AAC文件Adts解析&音频文件合成原理(JAVA基础方法实现）

package com.rex.media; import android.nfc.Tag; import android.util.Log; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.nio.ByteBuffer; import java.util.HashMap; import java.util.Map; /** * Created by Rex on 2018/3/31. */ public class AACHelper { // 采样频率对照表 private static Map<Integer, Integer> samplingFrequencyIndexMap = new HashMap<>(); static { samplingFrequencyIndexMap.put(96000, 0); samplingFrequencyIndexMap.put(88200, 1); samplingFrequencyIndexMap.put(64000, 2); samplingFrequencyIndexMap.put(48000, 3); samplingFrequencyIndexMap.put(44100, 4); samplingFrequencyIndexMap.put(32000, 5); samplingFrequencyIndexMap.put(24000, 6); samplingFrequencyIndexMap.put(22050, 7); samplingFrequencyIndexMap.put(16000, 8); samplingFrequencyIndexMap.put(12000, 9); samplingFrequencyIndexMap.put(11025, 10); samplingFrequencyIndexMap.put(8000, 11); samplingFrequencyIndexMap.put(0x0, 96000); samplingFrequencyIndexMap.put(0x1, 88200); samplingFrequencyIndexMap.put(0x2, 64000); samplingFrequencyIndexMap.put(0x3, 48000); samplingFrequencyIndexMap.put(0x4, 44100); samplingFrequencyIndexMap.put(0x5, 32000); samplingFrequencyIndexMap.put(0x6, 24000); samplingFrequencyIndexMap.put(0x7, 22050); samplingFrequencyIndexMap.put(0x8, 16000); samplingFrequencyIndexMap.put(0x9, 12000); samplingFrequencyIndexMap.put(0xa, 11025); samplingFrequencyIndexMap.put(0xb, 8000); } private AdtsHeader mAdtsHeader = new AdtsHeader(); private BitReader mHeaderBitReader = new BitReader(new byte[7]); private byte[] mSkipTwoBytes = new byte[2]; private FileInputStream mFileInputStream; private byte[] mBytes = new byte[1024]; /** * 构造函数，通过传递进来的文件路径创建输入流 * * @param aacFilePath AAC文件路径 * @throws FileNotFoundException */ public AACHelper(String aacFilePath) throws FileNotFoundException { mFileInputStream = new FileInputStream(aacFilePath); } public static int getHeaderLength(String aacFilePath) { FileInputStream in = null; int len = 0; try { in = new FileInputStream(aacFilePath); AdtsHeader adtsHeader = new AdtsHeader(); BitReader mHeaderBitReader = new BitReader(new byte[7]); if (in.read(mHeaderBitReader.buffer) < 7) { len = 0; return 0; } mHeaderBitReader.position = 0; int syncWord = mHeaderBitReader.readBits(12); // A if (syncWord != 0xfff) { throw new IOException("Expected Start Word 0xfff"); } adtsHeader.mpegVersion = mHeaderBitReader.readBits(1); // B adtsHeader.layer = mHeaderBitReader.readBits(2); // C adtsHeader.protectionAbsent = mHeaderBitReader.readBits(1); // D len = adtsHeader.getSize(); in.close(); } catch (IOException e) { Log.e("AACHelper", "aac解析错误" + e.toString()); e.printStackTrace(); } finally { if (len == 0) { Log.e("AACHelper", "aac解析错误,头文件长度获取失败"); } else { Log.e("AACHelper", "aac解析头部成功：len====" + len); } return len; } } /** * 获取下一Sample数据 * * @param byteBuffer 存放Sample数据的ByteBuffer * @return 当前Sample的byte[]大小，如果为空返回-1 * @throws IOException */ public int getSample(ByteBuffer byteBuffer) throws IOException { if (readADTSHeader(mAdtsHeader, mFileInputStream)) { int length = mFileInputStream.read(mBytes, 0, mAdtsHeader.frameLength - mAdtsHeader.getSize()); byteBuffer.clear(); byteBuffer.put(mBytes, 0, length); byteBuffer.position(0); byteBuffer.limit(length); return length; } return -1; } /** * 从AAC文件流中读取ADTS头部 * * @param adtsHeader ADTS头部 * @param fileInputStream AAC文件流 * @return 是否读取成功 * @throws IOException */ private boolean readADTSHeader(AdtsHeader adtsHeader, FileInputStream fileInputStream) throws IOException { if (fileInputStream.read(mHeaderBitReader.buffer) < 7) { return false; } mHeaderBitReader.position = 0; int syncWord = mHeaderBitReader.readBits(12); // A if (syncWord != 0xfff) { throw new IOException("Expected Start Word 0xfff"); } adtsHeader.mpegVersion = mHeaderBitReader.readBits(1); // B adtsHeader.layer = mHeaderBitReader.readBits(2); // C adtsHeader.protectionAbsent = mHeaderBitReader.readBits(1); // D adtsHeader.profile = mHeaderBitReader.readBits(2) + 1; // E adtsHeader.sampleFrequencyIndex = mHeaderBitReader.readBits(4); adtsHeader.sampleRate = samplingFrequencyIndexMap.get(adtsHeader.sampleFrequencyIndex); // F mHeaderBitReader.readBits(1); // G adtsHeader.channelconfig = mHeaderBitReader.readBits(3); // H adtsHeader.original = mHeaderBitReader.readBits(1); // I adtsHeader.home = mHeaderBitReader.readBits(1); // J adtsHeader.copyrightedStream = mHeaderBitReader.readBits(1); // K adtsHeader.copyrightStart = mHeaderBitReader.readBits(1); // L adtsHeader.frameLength = mHeaderBitReader.readBits(13); // M adtsHeader.bufferFullness = mHeaderBitReader.readBits(11); // 54 adtsHeader.numAacFramesPerAdtsFrame = mHeaderBitReader.readBits(2) + 1; // 56 if (adtsHeader.numAacFramesPerAdtsFrame != 1) { throw new IOException("This muxer can only work with 1 AAC frame per ADTS frame"); } if (adtsHeader.protectionAbsent == 0) { fileInputStream.read(mSkipTwoBytes); } return true; } /** * 释放资源 * * @throws IOException */ public void release() throws IOException { mFileInputStream.close(); } // /** // * 添加ADTS头部 // * // * @param packet ADTS header 的 byte[]，长度为7 // * @param packetLen 该帧的长度，包括header的长度 // */ // private void addADTStoPacket(byte[] packet, int packetLen) { // int profile = 2; // AAC LC // int freqIdx = 3; // 48000Hz // int chanCfg = 2; // 2 Channel // // packet[0] = (byte) 0xFF; // packet[1] = (byte) 0xF9; // packet[2] = (byte) (((profile - 1) << 6) + (freqIdx << 2) + (chanCfg >> 2)); // packet[3] = (byte) (((chanCfg & 3) << 6) + (packetLen >> 11)); // packet[4] = (byte) ((packetLen & 0x7FF) >> 3); // packet[5] = (byte) (((packetLen & 7) << 5) + 0x1F); // packet[6] = (byte) 0xFC; // } }