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 【关键字】

音频编码、管道模式、createEncoder

【写在前面】

在使用API6开发HarmonyOS应用时，如何将pcm源文件进行编码并写入文件，最后生成aac文件，本文直接附上主要代码开发步骤供大家参考。

【主要功能代码】

import ohos.media.codec.Codec;
import ohos.media.common.BufferInfo;
import ohos.media.common.Format;
import ohos.media.common.Source;import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;public class AudioEncoder {void creatEncoder(){}FileOutputStream fileOutputStream = null;public void encode(){System.out.println("encode start");try {File fd = new File("/data/data/com.example.myapplication/11.aac");fileOutputStream = new FileOutputStream(fd, true);} catch (FileNotFoundException e) {System.out.println("FileNotFoundException");} finally {}final Codec encoder = Codec.createEncoder();String path = "/data/data/com.example.myapplication/11.pcm";System.out.println("encoder = " + encoder);boolean ret = encoder.setSource(new Source(path), null);System.out.println("setSource ret = " + ret);Format fmt = new Format();// format格式中转码率和声道需与pcm相同fmt.putStringValue(Format.MIME, Format.AUDIO_AAC);fmt.putIntValue(Format.BIT_RATE, 128000);fmt.putIntValue(Format.CHANNEL, 2);fmt.putIntValue(Format.SAMPLE_RATE, 44100);fmt.putIntValue(Format.FRAME_RATE, 30); // 此设置必须，数值一般为30/60，或自行设置需要数值boolean b1 = encoder.setSourceFormat(fmt);System.out.println("setSourceFormat = " + b1);Codec.ICodecListener listener = new Codec.ICodecListener() {@Overridepublic void onReadBuffer(ByteBuffer byteBuffer, BufferInfo bufferInfo, int trackId) {System.out.println("byteBuffer = " + byteBuffer + "trackId = " + trackId + "bufferinfo = " + bufferInfo.bufferType);if(bufferInfo.bufferType == 4){encoder.stop();encoder.release();try {fileOutputStream.close();} catch (IOException e) {// 打印异常System.out.println("IOException");}return;}writeFile(byteBuffer,bufferInfo,trackId);}@Overridepublic void onError(int errorCode, int act, int trackId) {System.out.println( "PlayerCallback onError errorCode: "+errorCode +", trackId:"+trackId);}};boolean b = encoder.registerCodecListener(listener);System.out.println("registerCodecListener = " + b);boolean start = encoder.start();System.out.println("start = " + start);}private void writeFile(ByteBuffer outputBuffer, BufferInfo info, int trackId) {try {final byte[] chunk = new byte[info.size+7];addADTSHeader(chunk,info.size+7);outputBuffer.get(chunk,7,info.size);fileOutputStream.write(chunk);outputBuffer.clear();} catch (FileNotFoundException e) {System.out.println("FileNotFoundException");} catch (IOException e) {System.out.println("IOException");} finally {}}/*** 添加AAC帧文件头** @param packet    packet* @param packetLen packetLen*/private void addADTSHeader(byte[] packet, int packetLen) {int profile = 2; // AACint freqIdx = 4; // 44.1kHzint channelCount = 2;//声道packet[0] = (byte) 0xFF;packet[1] = (byte) 0xF9;packet[2] = (byte) (((profile - 1) << 6) + (freqIdx << 2) + (channelCount >> 2));packet[3] = (byte) (((channelCount & 3) << 6) + (packetLen >> 11));packet[4] = (byte) ((packetLen & 0x7FF) >> 3);packet[5] = (byte) (((packetLen & 7) << 5) + 0x1F);packet[6] = (byte) 0xFC;}
}

【说明和注意事项】

1、AAC文件有两种添加头文件方式：ADIF与ADTS，此处使用ADTS方式，ADTS是每一段编码都有一个头部，因此并不能只添加一次，需要在回调中添加头文件；添加头文件保存的aac文件可以直接播放；

2、format中需要设置FRAME_RATE，即fmt.putIntValue(Format.FRAME_RATE, 30);，数值必须大于0，否则可能会编码失败

3、编解码功能建议在子线程中执行，不要在主线程中。

【参考文档】

视频编解码文档：文档中心：视频编码