使用javacv中的FrameRecorder进行录像，录像的时候，调用record方法写帧数据和音频数据，这时候我们有一个需求，录像的同时，要把声音实时拿过来进行语音识别。

问题1：

语音识别用的是讯飞的SDK，要求声音采样率8k或16k。而设置FrameRecorder.setSampleRate(8000)后，再FrameRecorder.start()会报错，报错如下：

avcodec_encode_audio2() error 2: Could not encode audio packet.

问题2：

javacv官方录制demo中，从AudioRecord中read到的是ShortBuffer，而讯飞SDK方法要求传入byte，他的方法如下：

public void writeAudio(byte[] data, int start, int length) 

百度谷歌无果，只好自己研究。

解决问题1：

demo中默认设置FrameRecorder.setSampleRate(44100)没问题，我想到了一个办法，这个地方设置44100，在语音采集的地方设置8000，最后成功了。不过这个计算时间的方法要修改：

public static int getTimeStampInNsFromSampleCounted(int paramInt) {
//        return (int) (paramInt / 0.0441D);
        return (int) (paramInt / 0.0080D);
    }

解决问题2：

short数组转byte数组，注意数组长度变为原来的2倍

    public static byte[] short2byte(short[] sData) {
        int shortArrsize = sData.length;
        byte[] bytes = new byte[shortArrsize * 2];

        for (int i = 0; i < shortArrsize; i++) {
            bytes[i * 2] = (byte) (sData[i] & 0x00FF);
            bytes[(i * 2) + 1] = (byte) (sData[i] >> 8);
            sData[i] = 0;
        }
        return bytes;

    }

 /**
     * 录制音频的线程
     */
    class AudioRecordRunnable implements Runnable {
        short[] audioData;
        private final AudioRecord audioRecord;
        private int mCount = 0;
        int sampleRate = Constants.AUDIO_SAMPLING_RATE;


        private AudioRecordRunnable() {
            int bufferSize = AudioRecord.getMinBufferSize(sampleRate,
                    AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);
            audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, sampleRate,
                    AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, bufferSize);
            audioData = new short[bufferSize];


        }


        /**
         * 包含了音频的数据和起始位置
         *
         * @param buffer
         */
        private void record(Buffer buffer) {
            synchronized (mAudioRecordLock) {
                this.mCount += buffer.limit();
                if (!mIsPause) {
                    try {
                        if (mRecorder != null) {
                            mRecorder.record(sampleRate, new Buffer[]{buffer});
                        }
                    } catch (FrameRecorder.Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }


        /**
         * 更新音频的时间戳
         */
        private void updateTimestamp() {
            int i = Util.getTimeStampInNsFromSampleCounted(this.mCount);
            if (mAudioTimestamp != i) {
                mAudioTimestamp = i;
                mAudioTimeRecorded = System.nanoTime();
            }
        }


        public void run() {
            android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);
            if (audioRecord != null) {
                //判断音频录制是否被初始化
                while (this.audioRecord.getState() == 0) {
                    try {
                        Thread.sleep(100L);
                    } catch (InterruptedException localInterruptedException) {
                    }
                }
                this.audioRecord.startRecording();
                while ((runAudioThread)) {
                    updateTimestamp();
                    int bufferReadResult = this.audioRecord.read(audioData, 0, audioData.length);
                    if (bufferReadResult > 0) {
                        if (recording || (mVideoTimestamp > mAudioTimestamp)) {
                            record(ShortBuffer.wrap(audioData, 0, bufferReadResult));
                        }
                        if (SpeechManager.getInstance().isListening()) {
                            SpeechManager.getInstance().writeAudio(Util.short2byte(audioData), 0, bufferReadResult * 2);
                        }
                    }
                }
                SpeechManager.getInstance().stopListener();
                this.audioRecord.stop();
                this.audioRecord.release();
            }
        }
    }