android mp3转pcm

可以使用Android中的MediaExtractor和MediaCodec类来实现mp3到pcm的转换。

以下是一个简单的示例代码：

private void convertMP3toPCM(String mp3FilePath, String pcmFilePath) throws IOException {
    MediaExtractor extractor = new MediaExtractor();
    extractor.setDataSource(mp3FilePath);
    int trackIndex = selectTrack(extractor);
    extractor.selectTrack(trackIndex);

    MediaCodec codec = MediaCodec.createDecoderByType("audio/mpeg");
    codec.configure(extractor.getTrackFormat(trackIndex), null, null, 0);
    codec.start();

    ByteBuffer[] inputBuffers = codec.getInputBuffers();
    ByteBuffer[] outputBuffers = codec.getOutputBuffers();

    MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();
    boolean isEOS = false;
    long presentationTimeUs = 0;

    FileOutputStream fos = new FileOutputStream(pcmFilePath);
    BufferedOutputStream bos = new BufferedOutputStream(fos);

    while (!isEOS) {
        int inIndex = codec.dequeueInputBuffer(10000);
        if (inIndex >= 0) {
            ByteBuffer buffer = inputBuffers[inIndex];
            int sampleSize = extractor.readSampleData(buffer, 0);
            if (sampleSize < 0) {
                codec.queueInputBuffer(inIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                isEOS = true;
            } else {
                codec.queueInputBuffer(inIndex, 0, sampleSize, presentationTimeUs, 0);
                presentationTimeUs = extractor.getSampleTime();
                extractor.advance();
            }
        }

        int outIndex = codec.dequeueOutputBuffer(info, 10000);
        switch (outIndex) {
            case MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED:
                outputBuffers = codec.getOutputBuffers();
                break;
            case MediaCodec.INFO_OUTPUT_FORMAT_CHANGED:
                break;
            case MediaCodec.INFO_TRY_AGAIN_LATER:
                break;
            default:
                ByteBuffer buffer = outputBuffers[outIndex];
                byte[] chunk = new byte[info.size];
                buffer.get(chunk);
                buffer.clear();
                bos.write(chunk);
                codec.releaseOutputBuffer(outIndex, false);
                break;
        }

        if ((info.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
            isEOS = true;
        }
    }

    codec.stop();
    codec.release();
    extractor.release();
    bos.flush();
    bos.close();
    fos.close();
}

private int selectTrack(MediaExtractor extractor) {
    // Select the first audio track we find.
    int numTracks = extractor.getTrackCount();
    for (int i = 0; i < numTracks; i++) {
        MediaFormat format = extractor.getTrackFormat(i);
        String mime = format.getString(MediaFormat.KEY_MIME);
        if (mime.startsWith("audio/")) {
            return i;
        }
    }

    return -1;
}

需要注意的是，这段代码中的`selectTrack`方法用于选择第一个音频轨道，如果需要处理其他轨道，请根据实际情况进行修改。