// video device.
private Camera camera;
private MediaCodec vencoder;
private MediaCodecInfo vmci;
private MediaCodec.BufferInfo vebi;
private byte[] vbuffer;
// video camera settings.
private Camera.Size vsize;
private int vcolor;
private int vbitrate_kbps = 300;
private final static int VFPS = 20;
private
 
 final static int VGOP = 5;
private final static int VWIDTH = 640;
private final static int VHEIGHT = 480;

/* 首先需要初始化MediaCodec的配置 */
private void initMediaCodec() {
     // choose the right vencoder, perfer qcom then google.
    vcolor = chooseVideoEncoder();
    // vencoder yuv to 264 es stream.
    // requires sdk level 16+, Android 4.1, 4.1.1, the JELLY_BEAN
 

    try {
        vencoder = MediaCodec.createByCodecName(vmci.getName());
    } catch (IOException e) {
        Log.e(TAG, "create vencoder failed.");
        e.printStackTrace();
        return;
    }
    vebi = new MediaCodec.BufferInfo();
    // setup the vencoder.
    // @see https://developer.android.com/reference/android/media/MediaCodec.html
 

    MediaFormat vformat = MediaFormat.createVideoFormat(MediaFormat.MIMETYPE_VIDEO_AVC, vsize.width, vsize.height);
    vformat.setInteger(MediaFormat.KEY_COLOR_FORMAT, vcolor);
    vformat.setInteger(MediaFormat.KEY_MAX_INPUT_SIZE, 0);
    vformat.setInteger(MediaFormat.KEY_BIT_RATE, 1000 * vbitrate_kbps);
    vformat.setInteger(MediaFormat.KEY_FRAME_RATE, VFPS);
    vformat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, VGOP);
    Log.i(TAG, String.format("vencoder %s, color=%d, bitrate=%d, fps=%d, gop=%d, size=%dx%d",
            vmci.getName(), vcolor, vbitrate_kbps, VFPS, VGOP, vsize.width, vsize.height));
    // the following error can be ignored:
    // 1. the storeMetaDataInBuffers error:
    //      [OMX.qcom.video.encoder.avc] storeMetaDataInBuffers (output) failed w/ err -2147483648
    //      @see http://bigflake.com/mediacodec/#q12
    vencoder.configure(vformat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
    vencoder.start();
}

// for the vbuffer for YV12(android YUV), @see below:
// https://developer.android.com/reference/android/hardware/Camera.Parameters.html#setPreviewFormat(int)
// https://developer.android.com/reference/android/graphics/ImageFormat.html#YV12
private int getYuvBuffer(int width, int height) {
    // stride = ALIGN(width, 16)
    int stride = (int) Math.ceil(width / 16.0) * 16;
    // y_size = stride * height
    int y_size = stride * height;
    // c_stride = ALIGN(stride/2, 16)
    int c_stride = (int) Math.ceil(width / 32.0) * 16;
    // c_size = c_stride * height/2
    int c_size = c_stride * height / 2;
    // size = y_size + c_size * 2
    return y_size + c_size * 2;
}

// choose the video encoder by name.
private MediaCodecInfo chooseVideoEncoder(String name, MediaCodecInfo def) {
    int nbCodecs = MediaCodecList.getCodecCount();
    for (int i = 0; i < nbCodecs; i++) {
        MediaCodecInfo mci = MediaCodecList.getCodecInfoAt(i);
        if (!mci.isEncoder()) {
            continue;
        }
        String[] types = mci.getSupportedTypes();
        for (int j = 0; j < types.length; j++) {
            if (types[j].equalsIgnoreCase(VCODEC)) {
                //Log.i(TAG, String.format("vencoder %s types: %s", mci.getName(), types[j]));
                if (name == null) {
                    return mci;
                }

                if (mci.getName().contains(name)) {
                    return mci;
                }
            }
        }
    }
    return def;
}

// choose the right supported color format. @see below:
// https://developer.android.com/reference/android/media/MediaCodecInfo.html
// https://developer.android.com/reference/android/media/MediaCodecInfo.CodecCapabilities.html
private int chooseVideoEncoder() {
    // choose the encoder "video/avc":
    //      1. select one when type matched.
    //      2. perfer google avc.
    //      3. perfer qcom avc.
    vmci = chooseVideoEncoder(null, null);
    //vmci = chooseVideoEncoder("google", vmci);
    //vmci = chooseVideoEncoder("qcom", vmci);

    int matchedColorFormat = 0;
    MediaCodecInfo.CodecCapabilities cc = vmci.getCapabilitiesForType(VCODEC);
    for (int i = 0; i < cc.colorFormats.length; i++) {
        int cf = cc.colorFormats[i];
        Log.i(TAG, String.format("vencoder %s supports color fomart 0x%x(%d)", vmci.getName(), cf, cf));

        // choose YUV for h.264, prefer the bigger one.
        // corresponding to the color space transform in onPreviewFrame
        if ((cf >= cc.COLOR_FormatYUV420Planar && cf <= cc.COLOR_FormatYUV420SemiPlanar)) {
            if (cf > matchedColorFormat) {
                matchedColorFormat = cf;
            }
        }
    }
    for (int i = 0; i < cc.profileLevels.length; i++) {
        MediaCodecInfo.CodecProfileLevel pl = cc.profileLevels[i];
        Log.i(TAG, String.format("vencoder %s support profile %d, level %d", vmci.getName(), pl.profile, pl.level));
    }
    Log.i(TAG, String.format("vencoder %s choose color format 0x%x(%d)", vmci.getName(), matchedColorFormat, matchedColorFormat));
    return matchedColorFormat;
}