问无法通过Android MediaCodec API转换音频
EN

Stack Overflow用户

提问于 2015-06-25 09:09:38

回答 1查看 1.5K关注 0票数 3

我正在尝试编写一个基本的原始AAC数据到一个文件，希望我可以使用mp4parser封装它的视频轨道。为此，我需要将任何给定的音频文件编码成该格式。从API 16开始就可以使用MediaCodec API，因此我决定将其用于编解码器操作。

我不知道为什么网上没有很多关于这方面的资源，可能是因为相关的复杂性。虽然，我已经学会了基本的方法应该是：

通过MediaExtractor ->队列解码器输入缓冲区->去队列输出缓冲器获取样本数据，得到解码数据，-> Enqueue编码器输入缓冲区，->去队列编码器输出缓冲器->，将编码数据写入文件。

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();

}

由于某些原因，输出文件无效。为什么？

编辑:成功修复了一个异常，问题仍然存在。

编辑2:我通过将缓冲区大小设置为编码器格式设置中的比特率来防止缓冲区溢出。目前有两个问题: 1.经过很短的时间间隔后，它会被困在这里，可能会无限期地等待。int encInputBufferIndex = dequeueInputBuffer(-1); 2.解码所需的时间长短，为什么要考虑样本的实际间隔？

编辑3:使用AudioTrack.write()进行测试，音频播放得很好，但这并不是有意的，它表明解码是与被喂入的媒体文件同步进行的，这应该尽可能快地进行，以便编码器能够快速完成其工作。在decoder.queueInputBuffer()中更改presentationTimeUs没有任何作用。

java

android

android-mediacodec

mp4parser

数字工厂场景解决方案

帮助企业实现数字化、智能化，解决企业工厂内设备数据采集、设备指标分析、企业信息系统间数据孤岛打通、数据应用困难的问题

回答 1

Stack Overflow用户

发布于 2015-06-25 11:14:37

在正确的道路上，缺少的部分是使用MediaMuxer将编码的帧复制到有效的MediaMuxer文件中。在大片状上有一个很好的(也是唯一的)例子。有关这一问题的大多数相关实例如下

您将不得不合并和简化/修改它们，以处理音频而不是视频。您将需要上面的API 18

编辑：如何将解码器缓冲区转发给编码器(或多或少)。到目前为止，我还没有遇到缓冲区溢出的情况，只是希望理智的实现具有相同容量的编码器和解码器缓冲区：

int decoderStatus = audioDecoder.dequeueOutputBuffer(info, TIMEOUT_USEC);
  if (decoderStatus >= 0) {
      // no output available yet
      if (VERBOSE) Log.d(TAG, "no output from audio decoder available");
...
   } else if (decoderStatus == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
            audioDecoderOutputBuffers = audioDecoder.getOutputBuffers();
            if (VERBOSE) Log.d(TAG, "decoder output buffers changed (we don't care)");
    } else if (decoderStatus == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
            // expected before first buffer of data
            if (VERBOSE) {
                    MediaFormat newFormat = audioDecoder.getOutputFormat();
                    Log.d(TAG, "decoder output format changed: " + newFormat);
                }
    } else if (decoderStatus < 0) {
            Log.e(TAG, "unexpected result from decoder.dequeueOutputBuffer: "+decoderStatus);
            throw new RuntimeException("Issue with dencoding audio");
    } else { // decoderStatus >= 0
            if (VERBOSE) Log.d(TAG, "audio decoder produced buffer "
                                + decoderStatus + " (size=" + info.size + ")");

            if (info.size! = 0) {                           
                // Forward decoder buffer to encoder
                ByteBuffer decodedData = audioDecoderOutputBuffers[decoderStatus];
                decodedData.position(info.offset);
                decodedData.limit(info.offset + info.size);

                 // Possibly edit buffer data

                // Send it to the audio encoder.
                int encoderStatus = audioEncoder.dequeueInputBuffer(-1);
                if (encoderStatus < 0) {
                    throw new RuntimeException("Could not get input buffer for audio encoder!!!");
                }
            audioEncoderInputBuffers[encoderStatus].clear();
            audioEncoderInputBuffers[encoderStatus].put(decodedData);
         }
audioEncoder.queueInputBuffer(encoderStatus, 0, info.size, mAudioMediaTime, 0);
     if (VERBOSE) Log.d(TAG, "Submitted to AUDIO encoder frame, size=" + info.size + " time=" + mAudioMediaTime);
    }
 audioDecoder.releaseOutputBuffer(decoderStatus, false);