Android MediaCodec AMR-NB 实时解码

Question

我正在通过像 API 这样的套接字开发 VoIP。（使用窄带连接）

我需要对每个语音帧 (20ms) 进行编码并通过所述 api 发送，然后在另一端对其进行解码。

我尝试通过 NDK 与 Opus 合作，但它无处可去，所以我决定使用 MediaCodec 来 encode/decode 和 AMR-NB。

编码似乎有效，产生了预期大小的缓冲区（160 个原始字节到 20 个编码字节 + header 7.9Kbps）

但是当我处理编码缓冲区并尝试对其进行解码时，我收到了 INFO_OUTPUT_FORMAT_CHANGED 结果。

编码器：

// Set up recorder
    int recordBufferSize = AudioRecord.getMinBufferSize(SAMPLE_RATE, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT);
    arec = new AudioRecord(MediaRecorder.AudioSource.MIC, SAMPLE_RATE, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, recordBufferSize);

    // Set Up codec
    try {
        encoder = MediaCodec.createEncoderByType(MediaFormat.MIMETYPE_AUDIO_AMR_NB);
        MediaFormat format = new MediaFormat();
        format.setString(MediaFormat.KEY_MIME, MediaFormat.MIMETYPE_AUDIO_AMR_NB);
        format.setInteger(MediaFormat.KEY_SAMPLE_RATE, SAMPLE_RATE);
        format.setInteger(MediaFormat.KEY_CHANNEL_COUNT, 1);
        format.setInteger(MediaFormat.KEY_BIT_RATE, bitrate.getVal());
        encoder.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
    } catch (IOException e) {
        e.printStackTrace();
        return;
    }

    // Start Recording
    int read;
    byte[] buffer1 = new byte[bufferSize];

    ByteBuffer[] inputBuffers;
    ByteBuffer[] outputBuffers;

    ByteBuffer inputBuffer;
    ByteBuffer outputBuffer;

    MediaCodec.BufferInfo bufferInfo;
    int inputBufferIndex;
    int outputBufferIndex;

    byte[] outData;

    Frame frame;
    try {
        encoder.start();
        arec.startRecording();
        isRecording = true;
        while (isRecording) {
            read = arec.read(buffer1, 0, bufferSize);

            inputBuffers = encoder.getInputBuffers();
            outputBuffers = encoder.getOutputBuffers();
            inputBufferIndex = encoder.dequeueInputBuffer(-1);
            if (inputBufferIndex >= 0) {
                inputBuffer = inputBuffers[inputBufferIndex];
                inputBuffer.clear();

                inputBuffer.put(buffer1);

                encoder.queueInputBuffer(inputBufferIndex, 0, buffer1.length, 0, 0);
            }

            bufferInfo = new MediaCodec.BufferInfo();
            outputBufferIndex = encoder.dequeueOutputBuffer(bufferInfo, 0);


            while (outputBufferIndex >= 0) {
                outputBuffer = outputBuffers[outputBufferIndex];

                outputBuffer.position(bufferInfo.offset);
                outputBuffer.limit(bufferInfo.offset + bufferInfo.size);

                outData = new byte[bufferInfo.size];
                outputBuffer.get(outData);


                //-------------
                frame = new Frame(outData);
                handler.onFrameEncoded(frame);
                //------------

                encoder.releaseOutputBuffer(outputBufferIndex, false);
                outputBufferIndex = encoder.dequeueOutputBuffer(bufferInfo, 0);

            }
        }
        encoder.stop();
        arec.stop();
    } catch (Exception e) {
        e.printStackTrace();
    }

解码器：

@Override
        public void onFrameEncoded(Frame frame) {
            try {
                MediaCodec decoder = MediaCodec.createDecoderByType(MediaFormat.MIMETYPE_AUDIO_AMR_NB);
                MediaFormat format = new MediaFormat();
                format.setString(MediaFormat.KEY_MIME, MediaFormat.MIMETYPE_AUDIO_AMR_NB);
                format.setInteger(MediaFormat.KEY_SAMPLE_RATE, SAMPLE_RATE);
                format.setInteger(MediaFormat.KEY_CHANNEL_COUNT, 1);
                format.setInteger(MediaFormat.KEY_BIT_RATE, 7950);
                decoder.configure(format, null, null, 0);
                decoder.start();

                byte[] outData;

                ByteBuffer[] inputBuffers;
                ByteBuffer[] outputBuffers;

                ByteBuffer inputBuffer;
                ByteBuffer outputBuffer;

                MediaCodec.BufferInfo bufferInfo;
                int inputBufferIndex;
                int outputBufferIndex;
                inputBuffers = decoder.getInputBuffers();
                outputBuffers = decoder.getOutputBuffers();


                // Fill decoder input buffer
                inputBufferIndex = decoder.dequeueInputBuffer(-1);
                if (inputBufferIndex >= 0) {
                    inputBuffer = inputBuffers[inputBufferIndex];
                    inputBuffer.clear();

                    inputBuffer.put(frame.Buffer);

                    decoder.queueInputBuffer(inputBufferIndex, 0, frame.Buffer.length, 0, 0);
                }


                // Get Output
                bufferInfo = new MediaCodec.BufferInfo();
                outputBufferIndex = decoder.dequeueOutputBuffer(bufferInfo, -1);
                if (outputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) { // Just a check I threw in
                    MediaFormat format2 = decoder.getOutputFormat(); // Returns format RAW
                }

                while (outputBufferIndex >= 0) {
                    outputBuffer = outputBuffers[outputBufferIndex];

                    outputBuffer.position(bufferInfo.offset);
                    outputBuffer.limit(bufferInfo.offset + bufferInfo.size);

                    outData = new byte[bufferInfo.size];
                    outputBuffer.get(outData);


                    // Log.d("Decoder", outData.length + " bytes encoded");

                    decoder.releaseOutputBuffer(outputBufferIndex, false);
                    outputBufferIndex = decoder.dequeueOutputBuffer(bufferInfo, 0);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

我到处搜索 INFO_OUTPUT_FORMAT_CHANGED 但找不到任何可以帮助我的东西..

Answer 1

这是预期的行为。如果您使用的是 MediaMuxer，您会将 MediaFormat 传递给 addTrack()，这需要一些必须来自 MediaCodec 的信息。此行为是 added in API 18 引入 MediaMuxer 时。

参见 EncodeAndMuxTest 示例。

如果你没有使用 MediaMuxer，你可以忽略它。（您可能想要记录它只是为了确认一切都仍然是它应该的样子。）

Android MediaCodec AMR-NB 实时解码

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