jzman

mediaFormat.setInteger(MediaFormat.KEY_PCM_ENCODING, AudioFormat.ENCODING_PCM_FLOAT);

 static boolean isPcmFloat(MediaFormat format) {
  return format.getInteger(MediaFormat.KEY_PCM_ENCODING, AudioFormat.ENCODING_PCM_16BIT)
      == AudioFormat.ENCODING_PCM_FLOAT;
 }

// Assumes the buffer PCM encoding is 16 bit.
short[] getSamplesForChannel(MediaCodec codec, int bufferId, int channelIx) {
  	ByteBuffer outputBuffer = codec.getOutputBuffer(bufferId);
  	MediaFormat format = codec.getOutputFormat(bufferId);
  	ShortBuffer samples = outputBuffer.order(ByteOrder.nativeOrder()).asShortBuffer();
  	int numChannels = format.getInteger(MediaFormat.KEY_CHANNEL_COUNT);
  	if (channelIx < 0 || channelIx >= numChannels) {
    	return null;
  	}
 	short[] res = new short[samples.remaining() / numChannels];
  	for (int i = 0; i < res.length; ++i) {
    	res[i] = samples.get(i * numChannels + channelIx);
  	}
  	return res;
}

 MediaFormat format = decoder.getOutputFormat(…);
 int width = format.getInteger(MediaFormat.KEY_WIDTH);
 if (format.containsKey("crop-left") && format.containsKey("crop-right")) {
    width = format.getInteger("crop-right") + 1 - format.getInteger("crop-left");
 }
 int height = format.getInteger(MediaFormat.KEY_HEIGHT);
 if (format.containsKey("crop-top") && format.containsKey("crop-bottom")) {
    height = format.getInteger("crop-bottom") + 1 - format.getInteger("crop-top");
 }

// 獲取可用的輸入緩衝區的索引
public int dequeueInputBuffer (long timeoutUs)
// 獲取輸入緩衝區
public ByteBuffer getInputBuffer(int index)
// 將填滿數據的inputBuffer提交到編碼隊列
public final void queueInputBuffer(int index,int offset, int size, long presentationTimeUs, int flags)
// 獲取已成功編解碼的輸出緩衝區的索引
public final int dequeueOutputBuffer(BufferInfo info, long timeoutUs)
// 獲取輸出緩衝區
public ByteBuffer getOutputBuffer(int index)
// 釋放輸出緩衝區
public final void releaseOutputBuffer(int index, boolean render) 

// 創建MediaCodec進入Uninitialized子狀態
public static MediaCodec createByCodecName (String name)
public static MediaCodec createEncoderByType (String type)
public static MediaCodec createDecoderByType (String type)
// 配置MediaCodec進入Configured子狀態，crypto和descrambler會在後文中進行說明
public void configure(MediaFormat format, Surface surface, MediaCrypto crypto, int flags)
public void configure(MediaFormat format, @Nullable Surface surface,int flags, MediaDescrambler descrambler)
// Error
// 編解碼過程中遇到錯誤進入Error子狀態

// start之後立即進入Flushed子狀態
public final void start()
// 第一个输入缓冲区出队的时候进入Running子状态
public int dequeueInputBuffer (long timeoutUs)
// 输入缓冲区与流结束标记排队时，编解码器将转换为End-of-Stream子状态
// 此时MediaCodec将不接受其他输入缓冲区，但会生成输出缓冲区
public void queueInputBuffer (int index, int offset, int size, long presentationTimeUs, int flags)

// 編解碼完成結束後釋放MediaCodec進入釋放狀態(Released)
public void release ()

// 創建MediaCodec
public static MediaCodec createByCodecName (String name)
public static MediaCodec createEncoderByType (String type)
public static MediaCodec createDecoderByType (String type)

/**
 * 查詢指定MIME類型的編碼器
 */
fun selectCodec(mimeType: String): MediaCodecInfo? {
    val mediaCodecList = MediaCodecList(MediaCodecList.REGULAR_CODECS)
    val codeInfos = mediaCodecList.codecInfos
    for (codeInfo in codeInfos) {
        if (!codeInfo.isEncoder) continue
        val types = codeInfo.supportedTypes
        for (type in types) {
            if (type.equals(mimeType, true)) {
                return codeInfo
            }
        }
    }
    return null
}

// 獲取指定格式的編碼器
public String findEncoderForFormat (MediaFormat format)
// 獲取指定格式的解碼器
public String findDecoderForFormat (MediaFormat format)

// 是否軟解
public boolean isSoftwareOnly ()
// 是Android平台提供(false)還是廠商提供(true)的編解碼器
public boolean isVendor ()
// 是否支持硬件加速
public boolean isHardwareAccelerated ()
// 是編碼器還是解碼器
public boolean isEncoder ()
// 獲取當前編解碼器支持的合適
public String[] getSupportedTypes ()
// ...

// 硬解編解碼器
OMX.qcom.video.encoder.heic
OMX.qcom.video.decoder.avc
OMX.qcom.video.decoder.avc.secure
OMX.qcom.video.decoder.mpeg2
OMX.google.gsm.decoder
OMX.qti.video.decoder.h263sw
c2.qti.avc.decoder
...
// 軟解編解碼器
c2.android.aac.decoder
c2.android.aac.decoder
c2.android.aac.encoder
c2.android.aac.encoder
c2.android.amrnb.decoder
c2.android.amrnb.decoder
...

// 1. MediaFormat
// 創建MediaFormat
public static final MediaFormat createVideoFormat(String mime,int width,int height)
// 開啟或關閉功能，具體參見MediaCodeInfo.CodecCapabilities
public void setFeatureEnabled(@NonNull String feature, boolean enabled)
// 參數設置
public final void setInteger(String name, int value)

// 2. setCallback
// 如果使用的是異步處理數據的方式，在configure 之前要設置 MediaCodec.Callback
public void setCallback (MediaCodec.Callback cb)
public void setCallback (MediaCodec.Callback cb, Handler handler)

// 3. 配置
public void configure(MediaFormat format, Surface surface, MediaCrypto crypto, int flags)
public void configure(MediaFormat format, @Nullable Surface surface,int flags, MediaDescrambler descrambler)

// csd-0、csd-1、csd-2同理
val bytes = byteArrayOf(0x00.toByte(), 0x01.toByte())
mediaFormat.setByteBuffer("csd-0", ByteBuffer.wrap(bytes))

// 獲取輸入緩衝區(同步)
public int dequeueInputBuffer (long timeoutUs)
public ByteBuffer getInputBuffer (int index)
// 獲取輸出緩衝區(同步)
public int dequeueOutputBuffer (MediaCodec.BufferInfo info, long timeoutUs)
public ByteBuffer getOutputBuffer (int index)
// 輸入、輸出緩衝區索引從MediaCodec.Callback的回調中獲取，在獲取對應的輸入、輸出緩衝區(異步)
public void setCallback (MediaCodec.Callback cb)
public void setCallback (MediaCodec.Callback cb, Handler handler)
// 提交數據
public void queueInputBuffer (int index, int offset, int size, long presentationTimeUs, int flags)
public void queueSecureInputBuffer (int index, int offset, MediaCodec.CryptoInfo info, long presentationTimeUs, int flags)
// 釋放輸出緩衝區
public void releaseOutputBuffer (int index, boolean render)
public void releaseOutputBuffer (int index, long renderTimestampNs)

MediaCodec codec = MediaCodec.createByCodecName(name);
 codec.configure(format, …);
 MediaFormat outputFormat = codec.getOutputFormat(); // option B
 codec.start();
 for (;;) {
  int inputBufferId = codec.dequeueInputBuffer(timeoutUs);
  if (inputBufferId >= 0) {
    ByteBuffer inputBuffer = codec.getInputBuffer(…);
    // 使用有效數據填充輸入緩衝區
    …
    codec.queueInputBuffer(inputBufferId, …);
  }
  int outputBufferId = codec.dequeueOutputBuffer(…);
  if (outputBufferId >= 0) {
    ByteBuffer outputBuffer = codec.getOutputBuffer(outputBufferId);
    MediaFormat bufferFormat = codec.getOutputFormat(outputBufferId); // option A
    // bufferFormat與outputFormat是相同的
    // 輸出緩衝區已準備後被處理或渲染了
    …
    codec.releaseOutputBuffer(outputBufferId, …);
  } else if (outputBufferId == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
    // 輸出格式改變，後續採用新格式，此時使用getOutputFormat()獲取新格式
    // 如果使用getOutputFormat(outputBufferId)獲取特定緩衝區的格式，則無需監聽格式變化
    outputFormat = codec.getOutputFormat(); // option B
  }
 }
 codec.stop();
 codec.release();

MediaCodec codec = MediaCodec.createByCodecName(name);
 MediaFormat mOutputFormat; // member variable
 codec.setCallback(new MediaCodec.Callback() {
  @Override
  void onInputBufferAvailable(MediaCodec mc, int inputBufferId) {
    ByteBuffer inputBuffer = codec.getInputBuffer(inputBufferId);
    // fill inputBuffer with valid data
    …
    codec.queueInputBuffer(inputBufferId, …);
  }
 
  @Override
  void onOutputBufferAvailable(MediaCodec mc, int outputBufferId, …) {
    ByteBuffer outputBuffer = codec.getOutputBuffer(outputBufferId);
    MediaFormat bufferFormat = codec.getOutputFormat(outputBufferId); // option A
    // bufferFormat is equivalent to mOutputFormat
    // outputBuffer is ready to be processed or rendered.
    …
    codec.releaseOutputBuffer(outputBufferId, …);
  }
 
  @Override
  void onOutputFormatChanged(MediaCodec mc, MediaFormat format) {
    // Subsequent data will conform to new format.
    // Can ignore if using getOutputFormat(outputBufferId)
    mOutputFormat = format; // option B
  }
 
  @Override
  void onError(…) {
    …
  }
 });
 codec.configure(format, …);
 mOutputFormat = codec.getOutputFormat(); // option B
 codec.start();
 // wait for processing to complete
 codec.stop();
 codec.release();

// 創建輸入Surface，需在configure之後、start之前調用
public Surface createInputSurface ()
// 設置輸入Surface
public void setInputSurface (Surface surface)
// 發送流結束的信號
public void signalEndOfInputStream ()

// 設置輸出Surface
public void setOutputSurface (Surface surface)
// false表示不渲染這個buffer，true表示使用默認的時間戳渲染這個buffer
public void releaseOutputBuffer (int index, boolean render)
// 使用指定的時間戳渲染這個buffer
public void releaseOutputBuffer (int index, long renderTimestampNs)

// 是否支持某項功能，CodecCapabilities＃FEATURE_AdaptivePlayback對應對應自適應播放支持
public boolean isFeatureSupported (String name)

// true表示可以通過stop、configure、start來恢復
public boolean isRecoverable ()
// true表示暫時性問題，編碼或解碼操作會在後續重試進行
public boolean isTransient ()