在 Android 上将 wav 编码为 AAC

Question

您可以使用 MediaRecorder 将流直接录制到 AAC，但似乎没有将现有 PCM/WAV 文件编码为 AAC 的方法。 Android 本身就具有编码为 AAC 的功能，我想使用它。有没有办法用预先存在的音频文件来做到这一点？

Answer 1

看看这个美丽的（并且完美运行的）示例：
Mp4ParserSample

看看课程的最后部分（行335-442），convert Runnable 对象就可以完成这项工作！您必须根据需要调整代码，调整输入和输出文件路径以及转换参数（采样率、比特率等）。

public static final String AUDIO_RECORDING_FILE_NAME = "audio_Capturing-190814-034638.422.wav"; // Input PCM file
public static final String COMPRESSED_AUDIO_FILE_NAME = "convertedmp4.m4a"; // Output MP4/M4A file
public static final String COMPRESSED_AUDIO_FILE_MIME_TYPE = "audio/mp4a-latm";
public static final int COMPRESSED_AUDIO_FILE_BIT_RATE = 64000; // 64kbps
public static final int SAMPLING_RATE = 48000;
public static final int BUFFER_SIZE = 48000;
public static final int CODEC_TIMEOUT_IN_MS = 5000;
String LOGTAG = "CONVERT AUDIO";
Runnable convert = new Runnable() {
    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
    @Override
    public void run() {
        android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_BACKGROUND);
        try {
            String filePath = Environment.getExternalStorageDirectory().getPath() + "/" + AUDIO_RECORDING_FILE_NAME;
            File inputFile = new File(filePath);
            FileInputStream fis = new FileInputStream(inputFile);

            File outputFile = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/" + COMPRESSED_AUDIO_FILE_NAME);
            if (outputFile.exists()) outputFile.delete();

            MediaMuxer mux = new MediaMuxer(outputFile.getAbsolutePath(), MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);

            MediaFormat outputFormat = MediaFormat.createAudioFormat(COMPRESSED_AUDIO_FILE_MIME_TYPE,SAMPLING_RATE, 1);
            outputFormat.setInteger(MediaFormat.KEY_AAC_PROFILE, MediaCodecInfo.CodecProfileLevel.AACObjectLC);
            outputFormat.setInteger(MediaFormat.KEY_BIT_RATE, COMPRESSED_AUDIO_FILE_BIT_RATE);
            outputFormat.setInteger(MediaFormat.KEY_MAX_INPUT_SIZE, 16384);

            MediaCodec codec = MediaCodec.createEncoderByType(COMPRESSED_AUDIO_FILE_MIME_TYPE);
            codec.configure(outputFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
            codec.start();

            ByteBuffer[] codecInputBuffers = codec.getInputBuffers(); // Note: Array of buffers
            ByteBuffer[] codecOutputBuffers = codec.getOutputBuffers();

            MediaCodec.BufferInfo outBuffInfo = new MediaCodec.BufferInfo();
            byte[] tempBuffer = new byte[BUFFER_SIZE];
            boolean hasMoreData = true;
            double presentationTimeUs = 0;
            int audioTrackIdx = 0;
            int totalBytesRead = 0;
            int percentComplete = 0;
            do {
                int inputBufIndex = 0;
                while (inputBufIndex != -1 && hasMoreData) {
                    inputBufIndex = codec.dequeueInputBuffer(CODEC_TIMEOUT_IN_MS);

                    if (inputBufIndex >= 0) {
                        ByteBuffer dstBuf = codecInputBuffers[inputBufIndex];
                        dstBuf.clear();

                        int bytesRead = fis.read(tempBuffer, 0, dstBuf.limit());
                        Log.e("bytesRead","Readed "+bytesRead);
                        if (bytesRead == -1) { // -1 implies EOS
                            hasMoreData = false;
                            codec.queueInputBuffer(inputBufIndex, 0, 0, (long) presentationTimeUs, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                        } else {
                            totalBytesRead += bytesRead;
                            dstBuf.put(tempBuffer, 0, bytesRead);
                            codec.queueInputBuffer(inputBufIndex, 0, bytesRead, (long) presentationTimeUs, 0);
                            presentationTimeUs = 1000000l * (totalBytesRead / 2) / SAMPLING_RATE;
                        }
                    }
                }
                // Drain audio
                int outputBufIndex = 0;
                while (outputBufIndex != MediaCodec.INFO_TRY_AGAIN_LATER) {
                    outputBufIndex = codec.dequeueOutputBuffer(outBuffInfo, CODEC_TIMEOUT_IN_MS);
                    if (outputBufIndex >= 0) {
                        ByteBuffer encodedData = codecOutputBuffers[outputBufIndex];
                        encodedData.position(outBuffInfo.offset);
                        encodedData.limit(outBuffInfo.offset + outBuffInfo.size);
                        if ((outBuffInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0 && outBuffInfo.size != 0) {
                            codec.releaseOutputBuffer(outputBufIndex, false);
                        }else{
                            mux.writeSampleData(audioTrackIdx, codecOutputBuffers[outputBufIndex], outBuffInfo);
                            codec.releaseOutputBuffer(outputBufIndex, false);
                        }
                    } else if (outputBufIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                        outputFormat = codec.getOutputFormat();
                        Log.v(LOGTAG, "Output format changed - " + outputFormat);
                        audioTrackIdx = mux.addTrack(outputFormat);
                        mux.start();
                    } else if (outputBufIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
                        Log.e(LOGTAG, "Output buffers changed during encode!");
                    } else if (outputBufIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
                        // NO OP
                    } else {
                        Log.e(LOGTAG, "Unknown return code from dequeueOutputBuffer - " + outputBufIndex);
                    }
                }
                percentComplete = (int) Math.round(((float) totalBytesRead / (float) inputFile.length()) * 100.0);
                Log.v(LOGTAG, "Conversion % - " + percentComplete);
            } while (outBuffInfo.flags != MediaCodec.BUFFER_FLAG_END_OF_STREAM);
            fis.close();
            mux.stop();
            mux.release();
            Log.v(LOGTAG, "Compression done ...");
        } catch (FileNotFoundException e) {
            Log.e(LOGTAG, "File not found!", e);
        } catch (IOException e) {
            Log.e(LOGTAG, "IO exception!", e);
        }

        //mStop = false;
        // Notify UI thread...
    }
};

Answer 2

您可以亲自接触本机代码，并使用框架中的解码器的 IOMX C++ 接口。但这是构建敏感的，不适用于其他手机和 Android 版本。

另一种选择是移植一个开源 aac 编码器（如 ffmpeg），并通过 jni 编写一个应用程序。至少可以与具有相同架构的手机（arm-9、cortex a8..）配合使用。

JB 有一个 MediaCodec 来满足您的愿望。但问题是，JB 设备的安装基础将在一段时间内保持精简。

http://developer.android.com/about/versions/android-4.1 .html#多媒体

Answer 3

我认为你可以使用这个库。

https://github.com/timsu/android-aac-enc

http://betaful.com/post/82668810035/encoding-aac-audio-in-android