JavaCV音视频转单声道16位16K赫兹小端点pcm音频

　　先用Java CV的拉流对象实现对音视频的格式转换：

　　1、音视频转纯音频

　　2、音频指定采样率和声道　　

　　接着手动搞定采用率的位深，对音频做16位位深和小端点转换。最后把转好的字节数组写入文件，这个简单，用一个IO处理流对象搞定，看代码：

import org.bytedeco.javacv.FFmpegFrameGrabber;
import org.bytedeco.javacv.Frame;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.ShortBuffer;

/**
 * 音视频转单声道16位16K赫兹小端点pcm音频
 */
public class PCMFileProduce {

    public static void main(String[] args) throws Exception {
        String path = "E:\BaiduNetdiskDownload\roundDeskS02E01.mp4"; //待转音视频
        File file = new File("E:\BaiduNetdiskDownload\pcmTest.pcm"); //目标文件

        OutputStream os = new BufferedOutputStream(new FileOutputStream(file));

        FFmpegFrameGrabber frameGrabber = FFmpegFrameGrabber.createDefault(path);
        frameGrabber.setSampleRate(16000); //16K赫兹采样率
        frameGrabber.setAudioChannels(1); //单声道
        frameGrabber.start();

        Frame frame;
        Buffer buffer;
        short[] shorts;
        byte[] bytes;

        System.out.println("开始转换文件");
        while ((frame = frameGrabber.grabSamples()) != null) {
            if (frame.samples == null) {
                continue;
            }
            buffer = frame.samples[0];

            shorts = new short[buffer.limit()];
            ((ShortBuffer) buffer).get(shorts);
            bytes = shortArr2byteArr(shorts, buffer.limit());

            os.write(bytes);
        }

        os.close(); // 关闭写文件
        frameGrabber.close(); // 直接关闭拉流
        System.out.println("转换结束");
    }

    /**
     * 8位字节数组转16位字节数组，也就是16位的采样位深，转小端点字节数组
     *
     * @param shortArr
     * @param shortArrLen
     * @return
     */
    private static byte[] shortArr2byteArr(short[] shortArr, int shortArrLen) {
        byte[] byteArr = new byte[shortArrLen * 2];
        ByteBuffer.wrap(byteArr).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().put(shortArr);
        return byteArr;
    }

}

　　看输出：

Connected to the target VM, address: '127.0.0.1:50289', transport: 'socket'
开始转换文件
转换结束
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'E:BaiduNetdiskDownload
oundDeskS02E01.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.20.100
  Duration: 00:39:54.27, start: 0.000000, bitrate: 815 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1080x606, 744 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 64 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
Disconnected from the target VM, address: '127.0.0.1:50289', transport: 'socket'

Process finished with exit code 0

　　比较下ffmpeg和上面代码转换的两个文件：

　　命令行转换参见：ffmpeg音视频转单声道16位16K赫兹小端点pcm音频