Android平台GB28181设备接入端实现实时快照

Android平台GB28181设计开发的时候，有个功能必不可少的：实时快照，特别是用于执法记录仪等场景下，用于图像留底或分析等考量。

实时快照的实现并不难，目前实现有两种方式，一种是拿到数据（比如摄像头数据）后，直接上层编码，存取快照；另一种模式是，数据投递到JNI层，底层针对投递过来的编码前数据，做png编码，并保存到设定的目录下，今天我们主要探讨第二种实现模式。

我们在publisher实例初始化的时候，设置是否启用快照：

private void InitAndSetConfig() {

	int audio_opt = 1;

	int fps = 18;
	int gop = fps * 2;

	Log.i(TAG, "InitAndSetConfig video_width: " + video_width_ + " cur_video_height" + video_height_ + " imageRotationDegree:" + cameraImageRotationDegree_);

	publisherHandle = libPublisher.SmartPublisherOpen(context_, audio_opt, 3,  video_width_, video_height_);

	if (publisherHandle == 0) {
		Log.e(TAG, "sdk open failed!");
		return;
	}

	Log.i(TAG, "publisherHandle=" + publisherHandle);

	if(videoEncodeType == 1)  {
		int h264HWKbps = setHardwareEncoderKbps(true, video_width_, video_height_);
		h264HWKbps = h264HWKbps*fps/25;

		Log.i(TAG, "h264HWKbps: " + h264HWKbps);

		int isSupportH264HWEncoder = libPublisher
				.SetSmartPublisherVideoHWEncoder(publisherHandle, h264HWKbps);

		if (isSupportH264HWEncoder == 0) {
			libPublisher.SetNativeMediaNDK(publisherHandle, 1);
			Log.i(TAG, "Great, it supports h.264 hardware encoder!");
		}
	}
	else if (videoEncodeType == 2) {
		int hevcHWKbps = setHardwareEncoderKbps(false, video_width_, video_height_);
		hevcHWKbps = hevcHWKbps*fps/25;
		Log.i(TAG, "hevcHWKbps: " + hevcHWKbps);

		int isSupportHevcHWEncoder = libPublisher
				.SetSmartPublisherVideoHevcHWEncoder(publisherHandle, hevcHWKbps);

		if (isSupportHevcHWEncoder == 0) {
			libPublisher.SetNativeMediaNDK(publisherHandle, 1);
			Log.i(TAG, "Great, it supports hevc hardware encoder!");
		}
	}

	boolean is_sw_vbr_mode = true;
	if(is_sw_vbr_mode)	//H.264 software encoder
	{
		int is_enable_vbr = 1;
		int video_quality = CalVideoQuality(video_width_, video_height_, true);
		int vbr_max_bitrate = CalVbrMaxKBitRate(video_width_, video_height_);

		libPublisher.SmartPublisherSetSwVBRMode(publisherHandle, is_enable_vbr, video_quality, vbr_max_bitrate);
	}

	if (is_pcma_) {
		libPublisher.SmartPublisherSetAudioCodecType(publisherHandle, 3);
	} else {
		libPublisher.SmartPublisherSetAudioCodecType(publisherHandle, 1);
	}

	libPublisher.SetSmartPublisherEventCallbackV2(publisherHandle, new EventHandePublisherV2());

	libPublisher.SmartPublisherSetSWVideoEncoderProfile(publisherHandle, 3);

	libPublisher.SmartPublisherSetSWVideoEncoderSpeed(publisherHandle, 2);

	libPublisher.SmartPublisherSetGopInterval(publisherHandle, gop);

	libPublisher.SmartPublisherSetFPS(publisherHandle, fps);

	// libPublisher.SmartPublisherSetSWVideoBitRate(publisherHandle, 600, 1200);

	boolean is_noise_suppression = true;
	libPublisher.SmartPublisherSetNoiseSuppression(publisherHandle, is_noise_suppression ? 1 : 0);

	boolean is_agc = false;
	libPublisher.SmartPublisherSetAGC(publisherHandle, is_agc ? 1 : 0);

	int echo_cancel_delay = 0;
	libPublisher.SmartPublisherSetEchoCancellation(publisherHandle, 1, echo_cancel_delay);

	libPublisher.SmartPublisherSaveImageFlag(publisherHandle, 1);
}

记得留意最后一句：libPublisher.SmartPublisherSaveImageFlag(publisherHandle, 1);

相关接口说明如下：

 /**
  * Set if needs to save image during publishing stream(设置是否启用快照)
  *
  * @param is_save_image: if with 1, it will save current image via the interface of SmartPlayerSaveImage(), if with 0: does not it
  *
  * @return {0} if successful
  */
 public native int SmartPublisherSaveImageFlag(long handle,  int is_save_image);

设置后，页面有需要实时快照的数据时，点击“实时快照”按钮即可，需要注意的是，实时快照需要存储路径和保存下来的快照文件名称。具体实现如下：

class ButtonCaptureImageListener implements View.OnClickListener {
	@SuppressLint("SimpleDateFormat")
	public void onClick(View v) {
		if(isPushingRtmp || isRecording || isRTSPPublisherRunning || isGB28181StreamRunning)
		{
			String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
			String imageFileName = "dn_" + timeStamp;    //创建以时间命名的文件名称

			String imagePath = imageSavePath + "/" + imageFileName + ".png";

			Log.i(TAG, "imagePath:" + imagePath);

			libPublisher.SmartPublisherSaveCurImage(publisherHandle, imagePath);
		}
		else
		{
			Log.e(TAG, "快照失败，请确保在推送、录像、GB28181推送或内置RTSP服务发布状态..");
		}
	}
}

快照截取成功后，publisher实例会回调以下事件：

case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_CAPTURE_IMAGE:
	publisher_event = "快照: " + param1 + " 路径：" + param3;

	if (param1 == 0) {
		publisher_event = publisher_event + "截取快照成功..";
	} else {
		publisher_event = publisher_event + "截取快照失败..";
	}
	break;

由于实时快照，功能复杂度不高，而且也可以在上层实现，很容易被忽略，如果做的精细的话，还是需要开发者花费一定的心思。