android - 如何在 Android 中将音频原始格式转换为 flac

Question

我使用 audoiRecord 类录制音频。现在我想将音频原始文件转换为 *flac 格式。我接下来将 *raw 文件转换为 wav:

private void copyWaveFile(String inFilename,String outFilename){
    FileInputStream in = null;
    FileOutputStream out = null;
    long totalAudioLen = 0;
    long totalDataLen = totalAudioLen + 36;
    long longSampleRate = sampleRate;
    int channels = 2;
    long byteRate = RECORDER_BPP * sampleRate * channels/8;
    byte[] data_pcm = new byte[mAudioBufferSize];
    try {
        in = new FileInputStream(inFilename);
        out = new FileOutputStream(outFilename);
        totalAudioLen = in.getChannel().size();
        totalDataLen = totalAudioLen + 36;
        Log.i(TAG,"File size: " + totalDataLen);
        WriteWaveFileHeader(out, totalAudioLen, totalDataLen,
        longSampleRate, channels, byteRate);
        while(in.read(data_pcm) != -1){
            out.write(data_pcm);
        }
        in.close();
        out.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

这段代码负责文件头

private void WriteWaveFileHeader(
                 FileOutputStream out, long totalAudioLen,
                 long totalDataLen, long longSampleRate, int channels,
                 long byteRate) throws IOException {

     byte[] header = new byte[44];

     header[0] = 'R';  // RIFF/WAVE header
     header[1] = 'I';
     header[2] = 'F';
     header[3] = 'F';
     header[4] = (byte) (totalDataLen & 0xff);
     header[5] = (byte) ((totalDataLen >> 8) & 0xff);
     header[6] = (byte) ((totalDataLen >> 16) & 0xff);
     header[7] = (byte) ((totalDataLen >> 24) & 0xff);
     header[8] = 'W';
     header[9] = 'A';
     header[10] = 'V';
     header[11] = 'E';
     header[12] = 'f';  // 'fmt ' chunk
     header[13] = 'm';
     header[14] = 't';
     header[15] = ' ';
     header[16] = 16;  // 4 bytes: size of 'fmt ' chunk
     header[17] = 0;
     header[18] = 0;
     header[19] = 0;
     header[20] = 1;  // format = 1
     header[21] = 0;
     header[22] = (byte) channels;
     header[23] = 0;
     header[24] = (byte) (longSampleRate & 0xff);
     header[25] = (byte) ((longSampleRate >> 8) & 0xff);
     header[26] = (byte) ((longSampleRate >> 16) & 0xff);
     header[27] = (byte) ((longSampleRate >> 24) & 0xff);
     header[28] = (byte) (byteRate & 0xff);
     header[29] = (byte) ((byteRate >> 8) & 0xff);
     header[30] = (byte) ((byteRate >> 16) & 0xff);
     header[31] = (byte) ((byteRate >> 24) & 0xff);
     header[32] = (byte) (2 * 16 / 8);  // block align
     header[33] = 0;
     header[34] = RECORDER_BPP;  // bits per sample
     header[35] = 0;
     header[36] = 'd';
     header[37] = 'a';
     header[38] = 't';
     header[39] = 'a';
     header[40] = (byte) (totalAudioLen & 0xff);
     header[41] = (byte) ((totalAudioLen >> 8) & 0xff);
     header[42] = (byte) ((totalAudioLen >> 16) & 0xff);
     header[43] = (byte) ((totalAudioLen >> 24) & 0xff);

     out.write(header, 0, 44);
}

我不明白 *flac 文件的参数应该是什么

Answer 1

您需要一个编码器来将 pcm 数据转换为 flac 格式。您不能只更改标题并期望内容像 flac 一样工作。

Android(至少到 4.1)不包括 FLAC 编码器，尽管从 3.1 开始支持解码器(来源:http://developer.android.com/guide/appendix/media-formats.html)。

我没有直接经验，但看到有人使用 ffmpeg 作为 flac 编码器。本项目audioboo-android ，其中包含 native libFLAC/libFLAC++ 编码器，看起来很有趣。