Unable to transcode audio via Android MediaCodec API

I am trying to write basic raw AAC data to a file, in the hope that I can use mp4parser to encapsulate it with a video track. For this I need to encode any audio file in this format. The MediaCodec API is readily available since API 16, so I decided to use it to work with the codec.

I'm not sure why there aren't many resources available on the internet about this, perhaps because of the complexity. Although, I managed to find out that the fundamental approach should be:

Get sample data via MediaExtractor -> Enqueue decoder input buffer -> Unload output buffer and get decoded data -> Encoreue Encoder input buffer -> Dequeue decoder output buffer -> Write encoded data to file.

private void transcodeFile(File source, File destination) throws IOException {
    FileInputStream inputStream = new FileInputStream(source);
    FileOutputStream outputStream = new FileOutputStream(destination);

    log("Transcoding file: " + source.getName());

    MediaExtractor extractor;
    MediaCodec encoder;
    MediaCodec decoder;

    ByteBuffer[] encoderInputBuffers;
    ByteBuffer[] encoderOutputBuffers;
    ByteBuffer[] decoderInputBuffers;
    ByteBuffer[] decoderOutputBuffers;

    int noOutputCounter = 0;
    int noOutputCounterLimit = 10;

    extractor = new MediaExtractor();
    extractor.setDataSource(inputStream.getFD());
    extractor.selectTrack(0);

    log(String.format("TRACKS #: %d", extractor.getTrackCount()));
    MediaFormat format = extractor.getTrackFormat(0);
    String mime = format.getString(MediaFormat.KEY_MIME);
    log(String.format("MIME TYPE: %s", mime));


    final String outputType = MediaFormat.MIMETYPE_AUDIO_AAC;
    encoder = MediaCodec.createEncoderByType(outputType);
    MediaFormat encFormat = MediaFormat.createAudioFormat(outputType, 44100, 2);
    encFormat.setInteger(MediaFormat.KEY_BIT_RATE, 64000);
    encoder.configure(encFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);

    decoder = MediaCodec.createDecoderByType(mime);
    decoder.configure(format, null, null, 0);

    encoder.start();
    decoder.start();

    encoderInputBuffers = encoder.getInputBuffers();
    encoderOutputBuffers = encoder.getOutputBuffers();

    decoderInputBuffers = decoder.getInputBuffers();
    decoderOutputBuffers = decoder.getOutputBuffers();

    int timeOutUs = 1000;
    long presentationTimeUs = 0;

    MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();
    boolean inputEOS = false;
    boolean outputEOS = false;

    while(!outputEOS && noOutputCounter < noOutputCounterLimit) {
        noOutputCounter++;

        if(!inputEOS) {
            int decInputBufferIndex = decoder.dequeueInputBuffer(timeOutUs);
            log("decInputBufferIndex: " + decInputBufferIndex);
            if (decInputBufferIndex >= 0) {
                ByteBuffer dstBuffer = decoderInputBuffers[decInputBufferIndex];

                //Getting sample with MediaExtractor
                int sampleSize = extractor.readSampleData(dstBuffer, 0);
                if (sampleSize < 0) {
                    inputEOS = true;
                    log("Input EOS");
                    sampleSize = 0;
                } else {
                    presentationTimeUs = extractor.getSampleTime();
                }

                log("Input sample size: " + sampleSize);

                //Enqueue decoder input buffer
                decoder.queueInputBuffer(decInputBufferIndex, 0, sampleSize, presentationTimeUs, inputEOS ? MediaCodec.BUFFER_FLAG_END_OF_STREAM : 0);
                if (!inputEOS) extractor.advance();

            } else {
                log("decInputBufferIndex: " + decInputBufferIndex);
            }
        }

        //Dequeue decoder output buffer
        int res = decoder.dequeueOutputBuffer(info, timeOutUs);
        if(res >= 0) {
            if(info.size > 0) noOutputCounter = 0;

            int decOutputBufferIndex = res;
            log("decOutputBufferIndex: " + decOutputBufferIndex);

            ByteBuffer buffer = decoderOutputBuffers[decOutputBufferIndex];
            buffer.position(info.offset);
            buffer.limit(info.offset + info.size);

            final int size = buffer.limit();
            if(size > 0) {
                //audioTrack.write(buffer, buffer.limit(), AudioTrack.MODE_STATIC);

                int encInputBufferIndex = encoder.dequeueInputBuffer(-1);
                log("encInputBufferIndex: " + encInputBufferIndex);
                //fill the input buffer with the decoded data
                if(encInputBufferIndex >= 0) {
                    ByteBuffer dstBuffer = encoderInputBuffers[encInputBufferIndex];
                    dstBuffer.clear();
                    dstBuffer.put(buffer);

                    encoder.queueInputBuffer(encInputBufferIndex, 0, info.size, info.presentationTimeUs, 0);
                    int encOutputBufferIndex = encoder.dequeueOutputBuffer(info, timeOutUs);
                    if(encOutputBufferIndex >= 0) {
                        log("encOutputBufferIndex: " + encOutputBufferIndex);
                        ByteBuffer outBuffer = encoderOutputBuffers[encOutputBufferIndex];
                        byte[] out = new byte[outBuffer.remaining()];
                        outBuffer.get(out);
                        //write data to file
                        outputStream.write(out);
                    }
                }
            }
            decoder.releaseOutputBuffer(decOutputBufferIndex, false);
            if((info.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                outputEOS = true;
                log("Output EOS");
            }
        } else if (res == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
            decoderOutputBuffers = decoder.getOutputBuffers();
            log("Output buffers changed.");
        } else if (res == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
            log("Output format changed.");
        } else {
            log("Dequeued output buffer returned: " + res);
        }
    }

    log("Stopping..");
    releaseCodec(decoder);
    releaseCodec(encoder);
    inputStream.close();
    outputStream.close();

}

      

        
        
        
      

    

The output file is not valid for any reason. Why?

EDIT: Exception fixed, problem persists.

EDIT 2: I prevented the buffer overflow by setting the buffer size to bitrate in the encoder format settings. There are currently two questions: 1. After a very short period of time, he gets stuck here, possibly waiting indefinitely. int encInputBufferIndex = dequeueInputBuffer(-1);

 2. Decoding takes as long as a track, why does this refer to the actual sampling interval?

EDIT 3: Testing with AudioTrack.write (), the sound plays well and fine, but this is not intended and assumes that the decoding is in sync with the fed media file, it should be as fast as allowing the encoder to do its job quickly. Changing the TimeU representation in decoder.queueInputBuffer () did nothing.