在 Android 上将 wav 编码为 AAC [英] Encode wav to AAC on Android

问题描述

您可以使用 MediaRecorder 将流直接录制到 AAC 但似乎没有是一种将现有 PCM/WAV 文件编码为 AAC 的方法.编码为 AAC 的能力存在于 Android 中，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?

You can use MediaRecorder to record a stream directly to AAC but there doesn't seem to be a way to encode an existing PCM/WAV file to AAC. The ability to encode to AAC exists natively in Android and I'd like to use that. Is there no way to do it with a pre-existing audio file?

推荐答案

看看这个漂亮(而且工作完美)的例子:Mp4ParserSample

Look at this beautiful (and perfectly working) example: Mp4ParserSample

看看类的最后一部分(第 335-442 行)，convert Runnable 对象就完成了这项工作！您必须根据需要调整该代码，调整输入和输出文件路径以及转换参数(采样率、比特率等).

Look at the final part of the class (rows 335-442), the convert Runnable object just does the job! You have to shape that code to your needs, adjust the input and the output file paths and the conversion parameters (sampling rate, bit rate, etc).

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...
    }
};

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