蹩脚的编码mp3音频减慢- Android

Question

我一直在学习如何在Android上使用mp3。录音似乎是工作的，我得到一个输出作为mp3，但在播放音频已被减慢和音调下降。

我试着把所有相关的代码放在下面。能解释一下为什么会这样吗?提前感谢您的帮助。

编辑:好的，所以只是为了检查我导入原始数据到Audacity中，它播放得很好，所以这一定是编码阶段的一个问题。

Java类:

public class Record extends Activity implements OnClickListener {
    static {
        System.loadLibrary("mp3lame");
    }
    private native void initEncoder(int numChannels, int sampleRate, int bitRate, int mode, int quality);
    private native void destroyEncoder();
    private native int encodeFile(String sourcePath, String targetPath);
    private static final int RECORDER_BPP = 16;
    private static final String AUDIO_RECORDER_FILE_EXT_WAV = ".wav";
    private static final String AUDIO_RECORDER_FOLDER = "AberdeenSoundsites";
    private static final String AUDIO_RECORDER_TEMP_FILE = "record_temp.raw";
    private static final int[] RECORDER_SAMPLERATES = {44100, 22050, 11025, 8000};
    private static final int RECORDER_CHANNELS = AudioFormat.CHANNEL_IN_STEREO;
    private static final int RECORDER_AUDIO_ENCODING = AudioFormat.ENCODING_PCM_16BIT;
    public static final int NUM_CHANNELS = 2;
    public static final int SAMPLE_RATE = 44100;
    public static final int BITRATE = 320;
    public static final int MODE = 1;
    public static final int QUALITY = 2;
        private short[] mBuffer;
    private File rawFile;
    private File encodedFile;
    private int sampleRate;
    private String filename;
    private AudioRecord recorder = null;
    private int bufferSize = 0;
    private Thread recordingThread = null;
    private boolean isRecording = false;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.record);
        initEncoder(NUM_CHANNELS, SAMPLE_RATE, BITRATE, MODE, QUALITY);
        stopButton = (Button) findViewById(R.id.stop_button);
        stopButton.setOnClickListener(this);
        timer = (TextView) findViewById(R.id.recording_time);
        bufferSize = AudioRecord.getMinBufferSize(44100, RECORDER_CHANNELS, RECORDER_AUDIO_ENCODING);
    }
    private void startRecording() {
        stopped = false;
        stopButton.setText(R.string.stop_button_label);
        // Set up and start audio recording
        recorder = findAudioRecord();
        recorder.startRecording();
        isRecording = true;
        rawFile = getFile("raw");
        mBuffer = new short[bufferSize];
        startBufferedWrite(rawFile);
        }
    private void stopRecording() {
        mHandler.removeCallbacks(startTimer);
        stopped = true;
        if(recorder != null){
            isRecording = false;
            recorder.stop();
            recorder.release();
            recorder = null;
            recordingThread = null;
        }
        encodedFile = getFile("mp3");
        int result = encodeFile(rawFile.getAbsolutePath(), encodedFile.getAbsolutePath());
        if (result == 0) {
            Toast.makeText(Record.this, "Encoded to " + encodedFile.getName(), Toast.LENGTH_SHORT)
                    .show();
        }
    }
    private void startBufferedWrite(final File file) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                Looper.prepare();
                DataOutputStream output = null;
                try {
                    output = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file)));
                    while (isRecording) {
                        int readSize = recorder.read(mBuffer, 0, mBuffer.length);
                        for (int i = 0; i < readSize; i++) {
                            output.writeShort(mBuffer[i]);
                        }
                    }
                } catch (IOException e) {
                    Toast.makeText(Record.this, e.getMessage(), Toast.LENGTH_SHORT).show();
                } finally {
                    if (output != null) {
                        try {
                            output.flush();
                        } catch (IOException e) {
                            Toast.makeText(Record.this, e.getMessage(), Toast.LENGTH_SHORT).show();
                        } finally {
                            try {
                                output.close();
                            } catch (IOException e) {
                                Toast.makeText(Record.this, e.getMessage(), Toast.LENGTH_SHORT).show();
                            }
                        }
                    }
                }
            }
        }).start();
    }
    private File getFile(final String suffix) {
        Time time = new Time();
        time.setToNow();
        return new File(Environment.getExternalStorageDirectory()+"/MyAppFolder", time.format("%Y%m%d%H%M%S") + "." + suffix);
    }
    public AudioRecord findAudioRecord() {
        for (int rate : RECORDER_SAMPLERATES) {
            for (short audioFormat : new short[] { AudioFormat.ENCODING_PCM_16BIT, AudioFormat.ENCODING_PCM_8BIT }) {
                for (short channelConfig : new short[] { AudioFormat.CHANNEL_IN_STEREO, AudioFormat.CHANNEL_IN_MONO  }) {
                    try {
                        Log.d("AberdeenSoundsites", "Attempting rate " + rate + "Hz, bits: " + audioFormat + ", channel: "
                                + channelConfig);
                        int bufferSize = AudioRecord.getMinBufferSize(rate, channelConfig, audioFormat);
                        if (bufferSize != AudioRecord.ERROR_BAD_VALUE) {
                            // check if we can instantiate and have a success
                            AudioRecord recorder = new AudioRecord(MediaRecorder.AudioSource.MIC, rate, channelConfig, audioFormat, bufferSize);
                            sampleRate = rate;
                            if (recorder.getState() == AudioRecord.STATE_INITIALIZED)
                                return recorder;
                        }
                    } catch (Exception e) {
                        Log.e("MyApp", rate + "Exception, keep trying.",e);
                    }
                }
            }
        }
        Log.e("MyApp", "No settings worked :(");
        return null;
    }

C包装:

#include <stdio.h>
#include <stdlib.h>
#include <jni.h>
#include <android/log.h> 
#include "libmp3lame/lame.h"
#define LOG_TAG "LAME ENCODER"
#define LOGD(format, args...)  __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, format, ##args);
#define BUFFER_SIZE 8192
#define be_short(s) ((short) ((unsigned short) (s) << 8) | ((unsigned short) (s) >> 8))
lame_t lame;
int read_samples(FILE *input_file, short *input) {
    int nb_read;
    nb_read = fread(input, 1, sizeof(short), input_file) / sizeof(short);
    int i = 0;
    while (i < nb_read) {
        input[i] = be_short(input[i]);
        i++;
    }
    return nb_read;
}
void Java_myPacakage_myApp_Record_initEncoder(JNIEnv *env,
        jobject jobj, jint in_num_channels, jint in_samplerate, jint in_brate,
        jint in_mode, jint in_quality) {
    lame = lame_init();
    LOGD("Init parameters:");
    lame_set_num_channels(lame, in_num_channels);
    LOGD("Number of channels: %d", in_num_channels);
    lame_set_in_samplerate(lame, in_samplerate);
    LOGD("Sample rate: %d", in_samplerate);
    lame_set_brate(lame, in_brate);
    LOGD("Bitrate: %d", in_brate);
    lame_set_mode(lame, in_mode);
    LOGD("Mode: %d", in_mode);
    lame_set_quality(lame, in_quality);
    LOGD("Quality: %d", in_quality);
    int res = lame_init_params(lame);
    LOGD("Init returned: %d", res);
}
void Java_myPacakage_myApp_Record_destroyEncoder(
        JNIEnv *env, jobject jobj) {
    int res = lame_close(lame);
    LOGD("Deinit returned: %d", res);
}
void Java_myPacakage_myApp_Record_encodeFile(JNIEnv *env,
        jobject jobj, jstring in_source_path, jstring in_target_path) {
    const char *source_path, *target_path;
    source_path = (*env)->GetStringUTFChars(env, in_source_path, NULL);
    target_path = (*env)->GetStringUTFChars(env, in_target_path, NULL);
    FILE *input_file, *output_file;
    input_file = fopen(source_path, "rb");
    output_file = fopen(target_path, "wb");
    short input[BUFFER_SIZE];
    char output[BUFFER_SIZE];
    int nb_read = 0;
    int nb_write = 0;
    int nb_total = 0;
    LOGD("Encoding started");
    while (nb_read = read_samples(input_file, input)) {
        nb_write = lame_encode_buffer(lame, input, input, nb_read, output,
                BUFFER_SIZE);
        fwrite(output, nb_write, 1, output_file);
        nb_total += nb_write;
    }
    LOGD("Encoded %d bytes", nb_total);
    nb_write = lame_encode_flush(lame, output, BUFFER_SIZE);
    fwrite(output, nb_write, 1, output_file);
    LOGD("Flushed %d bytes", nb_write);
    fclose(input_file);
    fclose(output_file);
}

编辑 -好的，所以出于兴趣，我下载了教程提供的apk到我的手机上并运行了它。这很好。所以这意味着问题不在于教程，而在于我所做的事情。当我有时间的时候，我会重新检查一下，看看我是否能确定我错在哪里

Answer 1

你调用initEncoder与2通道，并初始化AudioRecord与STEREO和MONO，但wrapper.c只能处理1通道:

<>之前nb_write = lame_encode_buffer(lame, input, input, nb_read, output, BUFFER_SIZE);之前

以上代码要求源音频为单声道，有1个声道。如果希望支持STEREO，请注意lame_encode_buffer方法

<>之前int CDECL lame_encode_buffer (* gfp，/*全局上下文句柄*/const short int buffer_l[]，/*左通道的PCM数据*/const short int buffer_r[]，/*右通道的PCM数据*/Const int nsamples，/*每个通道的样本数*/unsigned char* mp3buf，/*指向已编码MP3流的指针*/Const int mp3buf_size;/*有效的字节数流 */

Answer 2

给你一个指针，你需要调用lame_encode_buffer_interleaved()如果你使用2通道(.stereo)来记录。

我花了几天时间才弄明白，这是你可以使用的代码:

if (lame_get_num_channels(glf) == 2)
{
    result = lame_encode_buffer_interleaved(glf, j_buffer_l, samples/2, j_mp3buf, mp3buf_size);
}
else
{
    result = lame_encode_buffer(glf, j_buffer_l, j_buffer_r, samples, j_mp3buf, mp3buf_size);
}

Answer 3

你激励我重新审视我的问题，我为自己找到了问题。也许这就是发生在你身上的事。检查您正在使用的wav文件的采样率。我以为或者看得太快了，以为上面写的是44100;但它是48000!我修复了我的问题:

lame_set_in_samplerate(lame, 48000);
lame_set_out_samplerate(lame, 44100);

也许你的代码没有读取正确的采样率为一些奇怪的原因?

Answer 4

你可以重写

nb_write = lame_encode_buffer(lame, input, input, nb_read, output, BUFFER_SIZE);

nb_write = lame_encode_buffer(lame, input1, input2, nb_read, output, BUFFER_SIZE);

并使用2个单声道原始文件作为输入。当然，您必须调整您的encodeFile -函数，以便它将两个字符串作为源并处理两次所有内容。