MediaCodec.jpg

MediaCodec 的整體流程如上圖所示，從input 輸入數(shù)據(jù)，從output 輸出數(shù)據(jù)，編碼的時候輸入的是原始數(shù)據(jù)，輸出的是編碼后的數(shù)據(jù)。

初始化

configure 編碼器的時候要將flag 設(shè)置為encode。

public void startEncode(MediaFormat format) {
    mFormat = format;
    final String mimeType = format.getString(MediaFormat.KEY_MIME);

    // Check to see if this is actually a video mime type. If it is, then create
    // a codec that can decode this mime type.
    try {
        mCodec = MediaCodec.createEncoderByType(mimeType);
    } catch (IOException e) {
        throw new RuntimeException(e);
    }
    mCodec.configure(format,null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
    mCodec.start();
}

寫數(shù)據(jù)

將原始數(shù)據(jù)送給 MediaCodec。

public void sendFrame(byte[] input, long pts, int flags) {
    int size = input.length;
    int inputBufferId = mCodec.dequeueInputBuffer(timeOut);
    if (inputBufferId >= 0) {
        // fill inputBuffers[inputBufferId] with valid data
        ByteBuffer buffer = mCodec.getInputBuffer(inputBufferId);
        buffer.put(input);
        mCodec.queueInputBuffer(inputBufferId, 0, size, pts, flags);
    }
}

取數(shù)據(jù)

從 MediaCodec 中取出編碼后的數(shù)據(jù)，這里要注意返回的outputBufferId，會有不同的處理。

public VEAVPacket receivePacket() {
    VEAVPacket packet = new VEAVPacket();
    int outputBufferId = mCodec.dequeueOutputBuffer(mBufferInfo, timeOut);
    if (outputBufferId == MediaCodec.INFO_TRY_AGAIN_LATER) {
        Log.d(TAG, "INFO_TRY_AGAIN_LATER");
        return packet;
    } else if (outputBufferId == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
        // Subsequent data will conform to new format.
        packet.format = mCodec.getOutputFormat();
        return packet;
    } else if (outputBufferId < 0) {
        Log.d(TAG, "receivePacket：" + outputBufferId);
        return packet;
    }
    // outputBuffers[outputBufferId] is ready to be processed or rendered.
    ByteBuffer outputBuffer = mCodec.getOutputBuffer(outputBufferId);
    if (outputBuffer == null) {
        return packet;
    }
    byte[] outData = new byte[mBufferInfo.size];
    outputBuffer.get(outData);
    packet.buffer = ByteBuffer.wrap(outData);
    packet.bufferInfo = mBufferInfo;
    mCodec.releaseOutputBuffer(outputBufferId, timeOut);

    return packet;
}

結(jié)束

public void stopEncode() {
  mCodec.stop();
  mCodec.release();
}

注意事項(xiàng)

封裝的時候可能提前需要獲取 sps 和 pps，然而編碼器接收到一定數(shù)據(jù)才會吐出這些信息，因此，我們可以先送入一些空數(shù)據(jù)，將這個信息給擠出來。

public MediaFormat getOutputFormat() {
    if (mOutFormat != null) {
        return mOutFormat;
    }
    byte [] data = new byte[1];

    long time = System.currentTimeMillis();
    sendFrame(data, time, 0);

    VEAVPacket videoPacket = receivePacket();
    if (videoPacket.format != null) {
        mOutFormat = videoPacket.format;
    }
    return mOutFormat;
}