先用Java CV的拉流物件實現對音視訊的格式轉換：

　　1、音視訊轉純音訊

　　2、音訊指定取樣率和聲道　　

　　接著手動搞定採用率的位深，對音訊做16位位深和小端點轉換。最後把轉好的位元組陣列寫入檔案，這個簡單，用一個IO處理流物件搞定，看程式碼：

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;

/**
 * 音視訊轉單聲道16位16K赫茲小端點pcm音訊
 */
public class PCMFileProduce {

    public static void main(String[] args) throws Exception {
        String path = "E:\\BaiduNetdiskDownload\\roundDeskS02E01.mp4"; //
 
待轉音視訊
        File file = new File("E:\\BaiduNetdiskDownload\\pcmTest.pcm"); //目標檔案

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

        FFmpegFrameGrabber frameGrabber = FFmpegFrameGrabber.createDefault(path);
        frameGrabber.setSampleRate(16000); //16K赫茲取樣率
        frameGrabber.setAudioChannels(1); //
 
單聲道
        frameGrabber.start();

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

        System.out.println("開始轉換檔案");
        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(); // 關閉寫檔案
        frameGrabber.close(); // 直接關閉拉流
        System.out.println("轉換結束");
    }

    /**
     * 8位位元組陣列轉16位位元組陣列，也就是16位的取樣位深，轉小端點位元組陣列
     *
     * @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;
    }

}

　　看輸出：

Connected to the target VM, address: '127.0.0.1:50289', transport: 'socket'
開始轉換檔案
轉換結束
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'E:\BaiduNetdiskDownload\roundDeskS02E01.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

　　比較下ffmpeg和上面程式碼轉換的兩個檔案：

　　命令列轉換參見：ffmpeg音視訊轉單聲道16位16K赫茲小端點pcm音訊