我在根据字节解析 mp3 文件中的数据时遇到问题。
第一部分输出是正确的,我有一个 254 秒长的 mp3 文件,我从 Github 的 mp3 解析库 mp3agic 中获取它的信息。
但是,关于帧长度和持续时间的信息的第二部分是不正确的。
Length of this mp3 is: 254 seconds
Bitrate: 320 kbps (CBR)
Sample rate: 44100 Hz
Has ID3v1 tag?: NO
Has ID3v2 tag?: YES
Has custom tag?: NO
framelength -1
framerate 38.28125
duration -271265.06
我用来获取帧长、帧率和持续时间的代码是:
File file = musicFile.getFileValue();
this.audioStream.startMusicStream(file);
try {
AudioInputStream audioInputStream = AudioSystem.getAudioInputStream(file);
AudioFormat format = audioInputStream.getFormat();
long audioFileLength = file.length();
int frameSize = format.getFrameSize();
float frameRate = format.getFrameRate();
float durationInSeconds = (audioFileLength / (frameSize * frameRate));
System.out.println("framelength "+frameSize);
System.out.println("framerate "+frameRate);
System.out.println("duration "+durationInSeconds);
this.setDurationLabel(durationInSeconds);
} catch (Exception e) {
e.printStackTrace();
}
首先,为什么 framelength 和其他测量值甚至是负值?那有什么意思?以及如何使用来自 audioinputstream 和 audioformat 的信息准确计算 mp3 文件的持续时间?
最佳答案
为我工作,感谢 JAAD 库 http://jaadec.sourceforge.net/ :
import net.sourceforge.jaad.aac.Decoder;
import net.sourceforge.jaad.aac.SampleBuffer;
import net.sourceforge.jaad.adts.ADTSDemultiplexer;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioInputStream;
import java.io.*;
public class AACHelper {
public static AudioInputStream decodeAAC(File inputFile) throws IOException {
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
AudioFormat audioFormat;
try {
final FileInputStream audioInputStream = new FileInputStream(inputFile);
final ADTSDemultiplexer adts = new ADTSDemultiplexer(audioInputStream);
final Decoder dec = new Decoder(adts.getDecoderSpecificInfo());
final SampleBuffer buf = new SampleBuffer();
byte[] b;
while (true) {
try {
b = adts.readNextFrame();
}
catch (Exception e) {
break;
}
dec.decodeFrame(b, buf);
outputStream.write(buf.getData());
}
audioFormat = new AudioFormat(buf.getSampleRate(), buf.getBitsPerSample(), buf.getChannels(), true, buf.isBigEndian());
LogUtils.i("FrameRate: " + audioFormat.getFrameRate());
LogUtils.i("FrameSize: " + audioFormat.getFrameSize());
LogUtils.i("SampleRate: " + buf.getSampleRate());
LogUtils.i("BitsPerSample: " + buf.getBitsPerSample());
LogUtils.i("Bitrate: " + buf.getBitrate());
LogUtils.i("Length: " + buf.getLength());
} finally {
// nop
}
byte[] outputStreamByteArray = outputStream.toByteArray();
ByteArrayInputStream inputStream = new ByteArrayInputStream(outputStreamByteArray);
AudioInputStream audioInputStream = new AudioInputStream(inputStream, audioFormat, outputStreamByteArray.length);
long audioFileLength = audioInputStream.getFrameLength();
int frameSize = audioFormat.getFrameSize();
float frameRate = audioFormat.getFrameRate();
double durationInSeconds = (audioFileLength / (frameSize * frameRate));
LogUtils.i("Duration: " + durationInSeconds);
return audioInputStream;
}
}
关于java - Java中音频文件的长度,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/35822397/