Question

问题很简单，但我没有任何解决方法：

我写了一行代码来在我的Nexus 4（Android 4.4.2）上创建AAC编码器

MediaCodec codec = MediaCodec.createEncoderByType("audio/mp4a-latm");

“codec”中保存的返回值不为null，但我在Logcat中收到一条红色错误消息：

03-20 15:25:08.985: E/OMXMaster(24517): A component of name 'OMX.qcom.audio.decoder.aac' already exists, ignoring this one.

我还试过另一行：

MediaCodec codec = MediaCodec.createByCodecName("OMX.google.aac.encoder");

并获得相同的错误结果。

在使用MediaCodec之前，我是否错过了任何初始化步骤？我在官方文件中没有找到任何相关信息。

有没有人遇到过这个问题？

实际上我正在尝试将PCM编码为AAC文件。我已经阅读了这个post @hubeir。他似乎已经成功了。我做了同样的事情：（1）设置mediacodec并输入PCM数据以获得编码帧。为此，我阅读了cts中的代码。每个编码的帧长度约为371-379。（2）将adts标题添加到框架，然后保存到文件。我一点一点地检查了头部，这是正确的。但该文件仍然无法播放。所以我想也许错误日志就是问题。

以下是我的整个代码，供参考：

MediaCodec codec = MediaCodec.createByCodecName("OMX.google.aac.encoder");      
MediaFormat format = new MediaFormat();
    format.setString(MediaFormat.KEY_MIME, "audio/mp4a-latm");
    format.setInteger(MediaFormat.KEY_AAC_PROFILE, 
                      MediaCodecInfo.CodecProfileLevel.AACObjectELD);
    format.setInteger(MediaFormat.KEY_SAMPLE_RATE, nSamplerate);
    format.setInteger(MediaFormat.KEY_BIT_RATE, 128000);
    format.setInteger(MediaFormat.KEY_CHANNEL_COUNT, nChannels);

    codec.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
    codec.start();

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

    boolean bEndInput = false;
    boolean bEndOutput = false;

while(true)
{
    if (!bEndInput)
    {
        int inputBufferIndex = codec.dequeueInputBuffer(0);
        if (inputBufferIndex >= 0)
        {
            int nLen = app.readPCM(nHandle,inputBuffers[inputBufferIndex]);//This line read PCM, return 0 if end of data.
            int nBufLen = inputBuffers[inputBufferIndex].capacity(); 
            if (nLen == nBufLen)
                codec.queueInputBuffer(inputBufferIndex, 0, nLen, 0,  MediaCodec.BUFFER_FLAG_SYNC_FRAME);
            else if (nLen < nBufLen)
            {
                codec.queueInputBuffer(inputBufferIndex, 0, nLen, 0,  MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                bEndInput = true;
                break;
            }   
        }
    }

    MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();
    if (!bEndOutput)
    {
            int outputBufferIndex = codec.dequeueOutputBuffer(info, 0);
            if (outputBufferIndex  >= 0)
            {
                int outBitsSize   = info.size;
                Log.d("test", "Offset:"+info.offset);
                Log.d("test", "Size:"+info.size);
                Log.d("test", "Time:"+info.presentationTimeUs);
                Log.d("test", "Flags:"+info.flags);
                if (outBitsSize <= 10)
                {
                    codec.releaseOutputBuffer(outputBufferIndex, false /* render */);
                    continue;
                }

                int outPacketSize = outBitsSize + 7;    // 7 is ADTS size
                ByteBuffer outBuf = outputBuffers[outputBufferIndex];

                outBuf.position(info.offset);
                outBuf.limit(info.offset + outBitsSize);
                try {
                    byte[] data = new byte[outPacketSize];  //space for ADTS header included
                    addADTStoPacket(data, outPacketSize);
                    outBuf.get(data, 7, outBitsSize);
                    outBuf.position(info.offset);
                    outputStream.write(data, 0, outPacketSize);  //open FileOutputStream beforehand
                } catch (IOException e) {
                    Log.e("test", "failed writing bitstream data to file");
                    e.printStackTrace();
                }

                outBuf.clear();
                codec.releaseOutputBuffer(outputBufferIndex, false /* render */);
                Log.d("test", "  dequeued " + outBitsSize + " bytes of output data.");
                Log.d("test", "  wrote " + outPacketSize + " bytes into output file.");

                if (info.flags == MediaCodec.BUFFER_FLAG_END_OF_STREAM)
                {
                    bEndOutput = true;
                    //break;
                }   
            }
            else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) 
            {
                 outputBuffers = codec.getOutputBuffers();
            } 
            else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) 
            {

            }
    }

    if (bEndInput && bEndOutput)
        break;
}

Answer 1

我弄清楚了。

（1）媒体格式的错误设置：

format.setInteger(MediaFormat.KEY_AAC_PROFILE, 
                      MediaCodecInfo.CodecProfileLevel.AACObjectELD);

应该是

format.setInteger(MediaFormat.KEY_AAC_PROFILE, 
                      MediaCodecInfo.CodecProfileLevel.AACObjectLC);

（2）只有当（info.flags == 0）

时，编码的帧才可以用adts文件写入文件

（3）输出文件名后缀应为＆＃34; aac ＆＃34;。＆＃34;的 MP4 ＆＃34;或＆＃34; m4a ＆＃34;可能不适用于某些应用程序。

MediaCodec codec = MediaCodec.createByCodecName("OMX.google.aac.encoder"); MediaFormat format = new MediaFormat(); format.setString(MediaFormat.KEY_MIME, "audio/mp4a-latm"); format.setInteger(MediaFormat.KEY_AAC_PROFILE, MediaCodecInfo.CodecProfileLevel.AACObjectLC); //fixed version format.setInteger(MediaFormat.KEY_SAMPLE_RATE, nSamplerate); format.setInteger(MediaFormat.KEY_BIT_RATE, 128000); format.setInteger(MediaFormat.KEY_CHANNEL_COUNT, nChannels); codec.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE); codec.start(); ByteBuffer[] inputBuffers = codec.getInputBuffers(); ByteBuffer[] outputBuffers = codec.getOutputBuffers(); boolean bEndInput = false; boolean bEndOutput = false; while(true) { if (!bEndInput) { int inputBufferIndex = codec.dequeueInputBuffer(0); if (inputBufferIndex >= 0) { int nLen = app.readPCM(nHandle,inputBuffers[inputBufferIndex]);//This line read PCM, return 0 if end of data. int nBufLen = inputBuffers[inputBufferIndex].capacity(); if (nLen == nBufLen) codec.queueInputBuffer(inputBufferIndex, 0, nLen, 0, MediaCodec.BUFFER_FLAG_SYNC_FRAME); else if (nLen < nBufLen) { codec.queueInputBuffer(inputBufferIndex, 0, nLen, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM); bEndInput = true; break; } } } MediaCodec.BufferInfo info = new MediaCodec.BufferInfo(); if (!bEndOutput) { int outputBufferIndex = codec.dequeueOutputBuffer(info, 0); if (outputBufferIndex >= 0) { int outBitsSize = info.size; Log.d("test", "Offset:"+info.offset); Log.d("test", "Size:"+info.size); Log.d("test", "Time:"+info.presentationTimeUs); Log.d("test", "Flags:"+info.flags); if (info.flags != 0) //fixed version { codec.releaseOutputBuffer(outputBufferIndex, false /* render */); continue; } int outPacketSize = outBitsSize + 7; // 7 is ADTS size ByteBuffer outBuf = outputBuffers[outputBufferIndex]; outBuf.position(info.offset); outBuf.limit(info.offset + outBitsSize); try { byte[] data = new byte[outPacketSize]; //space for ADTS header included addADTStoPacket(data, outPacketSize); outBuf.get(data, 7, outBitsSize); outBuf.position(info.offset); outputStream.write(data, 0, outPacketSize); //open FileOutputStream beforehand } catch (IOException e) { Log.e("test", "failed writing bitstream data to file"); e.printStackTrace(); } outBuf.clear(); codec.releaseOutputBuffer(outputBufferIndex, false /* render */); Log.d("test", " dequeued " + outBitsSize + " bytes of output data."); Log.d("test", " wrote " + outPacketSize + " bytes into output file."); if (info.flags == MediaCodec.BUFFER_FLAG_END_OF_STREAM) { bEndOutput = true; //break; } } else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) { outputBuffers = codec.getOutputBuffers(); } else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) { } } if (bEndInput && bEndOutput) break; }

Answer 2

请查看设备文件夹下的media_codecs_xxxx.xml （注意：xxxx通常取决于您的硬件平台）。

这里你可能有OMX.qcom.audio.decoder.aac和 OMX.google.aac.encoder.Please使用其中任何一个并评论其他

请参阅https://source.android.com/devices/media.html（将编解码器公开给框架），这会对你有所帮助

Answer 3

有趣的是，前段时间我在某些设备上遇到了类似问题：如果使用MediaCodec.createEncoderByType（），则会创建AAC解码器而不是编码器。为了解决这个问题，我使用了：

  String codecName = selectEncoder(mime);
  mediaCodec = MediaCodec.createByCodecName(codecName);

和

  private String selectEncoder(String mime) {
    for (int index = 0; index < MediaCodecList.getCodecCount(); index++) {
        MediaCodecInfo codecInfo = MediaCodecList.getCodecInfoAt(index);

        if (!codecInfo.isEncoder()) {
            continue;
        }

        for (String type : codecInfo.getSupportedTypes()) {
            if (type.equalsIgnoreCase(mime)) {
                return codecInfogetName();
            }
        }
    }
    return null;
 }

类似的东西

使用MediaCodec创建AAC编码器时出错

3 个答案: